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31 featured content items: Featured articles (30) H, He, O, F, Zn, Ge, Y, Nb, Tc, Xe, Cs, Pb, At, Fr, Th, U, Pu, Cf, Db, Hs, Nh, Ts, Og, noble gas, metalloid, periodic table, heavy metals, radiocarbon dating, history of aluminium, island of stability Featured topics (1) period 1 elements Signpost interviews: 2011, 2013 Detailed list Article quality in the periodic table Other high-quality articles

Deprecated, last update Dec 2020; Regular archive Wikipedia talk:WikiProject Elements/Archive 60 -14:29, 10 December 2022 (UTC)

Long-term topics in WP:ELEMENTS
Isotopes WikiProject Isotopes is now incorporated into WikiProject Elements (see Archive 21)
Categories commons: Category:Periodic table, Category:Periodic tables using the enwiki classifications Metalloids, categorisation, including the categorising of astatine (2013; archive 15) Reclassifying nonmetals (2017/2018; archive 35 et al.)
The location and constitution of Group 3 Group 3 constitution (2017; Periodic table/archive 9) Group 3 (tyranny of blocks; arguments) (2018; archive 33) A conclusive argument for group_3, ... (Dec 2018–Mar 2019; Archive 38). A follow up is in #IUPAC and Group 3 (bifurcation), see also this PT (Apr 2019) Archive #42, #44, #46, #48: The location and constitution of Group 3 of the periodic table (Dec 2019–Aug 2020)
Periodic table More generally (Oct 2020)
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Periodic ziggurat of the elements

Extended content

This is based on gas phase electron configurations. There is a lot going on here. There are two images as I couldn't get the whole thing onto one screen with sufficient resolution. Every time I worked on it there was something else needing fixing. I hope I have it right now. @Double sharp: I'd be especially grateful for any thoughts on the An and super-heavies as far as whether I got them right. Our articles on these elements have been so helpful. Sandbh (talk) 08:14, 5 July 2020 (UTC) @Sandbh: As we can see strongly from this, the waves thrusting the gas-phase configurations here and there don't strongly result in anything consistent. In the d-block we can see lots of almost totally identical pairs like Nb-Ta and Mo-W which seem to not care at all about having different gas-phase configurations. And likewise in the f-block we see extremely different pairs like Sm-Pu with the same configuration. And compare both to the not very good resemblances Sn-Pb and Sb-Bi. ^_^ Note that this table clearly shows the superiority of Lu under Y, in avoiding Lu and Lr hanging around in the f block past the fully filled subshell and with no possibility of using their f electrons for chemistry. Critique of all notes: A. If we are allowing predictions, note that caesium is predicted to do much the same under pressure, acting like a seventh 5p element after Xe. In fact there have even been some vague experimental indications that it may be possible to get the Cs3+ even without the pressure (Greenwood and Earnshaw, p. 83), though nothing confirmed yet. B. Two points for this one. B.1. If you look at 2nd, 3rd, 4th IEs you can easily get high numbers that don't actually make sense with periodicity. The alkali metals will surely get you very high numbers for all of that. You have to instead look at what you're doing. Outside the transition metals, the first IE makes by far the most sense, as that is going straight from the neutral configuration, so you can immediately see where the half- and fully-filled shells are. Indeed, you get a peak at nitrogen and a fall to oxygen, that's perfect. Notice that you do not get this peak going from antimony to tellurium, in keeping with the trend that this effect diminishes for later and later periods. For transition metals (d and f blocks), then the third one makes more sense because usually the s electrons go first before the d and f ones go. B.2. Saying "low EA" are seen for Gd-Cm is rather missing the point. Here are the values for the f elements in kJ/mol: La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb 54 55 11 9 12 16 11 13 13 ≥34 33 30 99 0 Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No 34 113 53 51 46 0 10 27 0 0 0 34 94 0 Of course, you know what I think of negative EA. That's why I put zeroes instead of those negative numbers. But even if you don't, I think it's fairly obvious that you really cannot single out Eu-Am or Gd-Cm as being especially "low" alone. Tb is about the same as Gd, Bk is zero unlike positive Cm. So? The only thing we can consistently say here seems to be that as usual the zero value happens at the end of the block. As usual this is broken by gatecrasher Lu in the La table, even if not by Lr for once. C. What "dip" for tellurium? If you actually plotted it you'd find that the dip shrinks in each period until it goes away (continuum again). Terbium 1st IE is irrelevant to its position, see B.1. The relevant 3rd IE shows the expected strong dip at gadolinium. D. Yet again the 1st IE is irrelevant for these elements, you want the 3rd one. (Of course it should be noted that La and Ac in the d-block look like clear outliers.) E. Probably roentgenium will not form the −1 state. Predicted EA is closer to silver (which doesn't) than gold (which does). F. That's not its real electronegativity, that's because of cluster formation. Au is similarly overestimated by Pauling. G. and H. OK. I. and J. It's not "inaccessible". 1s in He is no problem to involve itself in bonding in charged compounds like HeH+, same thing for Ne 2p and Ar 3p. Neutral compounds are the problem. K. OK. L. I don't know if this means much of anything looking at the weirdness in the f-block (see point B.2). M. It's not "inaccessible" either. 3d contributes to the bonding in ZnF2, as previously presented here with sources. It's part of the valence MOs. N. See B.2. O. Correct. And a good sign that they are not f-block elements at all, since the f subshell is to the contrary accessible in La, Ac, and Th. P.1. The exact same thing has happened for La and Ac. Both have some delocalisation into the f subshell which overlaps the other valence bands and indeed they both have the "wrong" crystal structure for the group 3 column. Of course for this one it is just adding fuel to the fire with increasing d occupation in the metal as the atom gets bigger, but f participation and occupancy also is concurrently getting bigger (see Gschneidner) and is responsible for high coordination numbers and low melting points. P.2. ThIII in chemical environments is almost always 6d1, not 5f1. Double sharp (talk) 04:31, 6 July 2020 (UTC)

I would readily describe this PT as not being "groupic", but I would not say the same about "our" enwiki PT. (See special:diff/973773980) YBG (talk) 05:40, 1 September 2020 (UTC)

The periodic system landscape

Physics- philosophy	Proposed standard classroom version	Stowe's physicist's table Platonic, Left step, or Janet table	Henry Bent's line ADOMAH Periodic round table
	IUPAC 15LaAc  (old version)	14CeTh	14LaAc Landau & Lifshitz table Metallurgist's periodic table Quantum fold table
Chemistry	Inorganic chemist's table Alexander Arrangement Deming's table	Mendeleev's short form Giguère's Periodic Table	Benfey's spiral Octagonal prismatic PT
	Didactic		Designer-Aesthetic

Scerri (2020) talks about a continuum of periodic systems, with Rayner-Canham's unruly inorganic chemist's table at one end, and the left-step or Platonic periodic table at the other end. Somewhere in the middle is the currently popular 18-column table.

This is the physics—chemistry axis.

Cao et al. (2019) talk about chemical, pedagogic, and designer periodic tables.

This is the didactic—designer axis.

Combining the two axes results in a 3 × 3 grid, as shown.

The example placements are rough first go’s.

I probably need to expand the grid into a 5 x 5, and place the systems on the basis of a score out of 5 for each axis. Sandbh (talk) 06:29, 20 July 2020 (UTC)

• Cao C, Hu H, Li J, and Schwarz WHE 2019, "Physical origin of chemical periodicities in the system of elements", Pure & Applied Chemistry vol. 91, pp. 1969–1999
• Scerri E 2020, The periodic table: Its story and significance, 2nd ed., Oxford University Press, New York, pp. 402–403

• There's much to explore here, but from start there is this re the Proposed standard classroom version:

The confusion results from the false premise that the 18-column periodic table is derived from a "superior" 32-column periodic table by cutting and pasting the f-block below it.

— Brian Gregory, The Global Periodic Table and a Proposed Standard Classroom Version

Here the author is introducing/claiming a significant difference between the two forms. Even worse: for a classroom PT. Hope to to have more time for this shortly. -DePiep (talk) 15:51, 12 August 2020 (UTC)

From symmetry-regularity to asymmetry-irregularity: The texture of the world

[From] symmetry-regularity:

Tier	Notes
1a	Protons = regular = LSPT triads' 2nd/3rd members occur in periods of equal lengths^
1b	Electrons = regular arrangement = Madelung rule regular electron configurations

…via symmetry breaking

[to] asymmetry-irregularity:

Tier	Detail	Boundary
2	Electrons = ~20 imperfections	Madelung rule snap-back†
3	Neutrons = 254 stable isotopes	Neutron: proton ratio ≤ phi (golden ratio)
4	Elements = many irregularities	Hsueh & Chiang (1937); -AR-EA-IE-EN- ring
5	Periodic systems = 1,000+	Physics—Chemistry × Didactic—Designer matrix

^ see doi:10.1002/chem.201900460. Fig. 8
† after each variation from the MR the filling sequence returns to normal

Table updated Sandbh (talk) 12:21, 23 August 2020 (UTC)

--- Sandbh (talk) 07:31, 22 July 2020 (UTC)

If you cannot make a legible statement, Sandbh, then remove this post yourself please. -DePiep (talk) 00:24, 25 July 2020 (UTC)

Regularity and symmetry

It's curious that interest in the regularity and symmetry of periodic system representations has some basis in Z and the Madelung Rule. Yet the MR sort of has some bumps in it, and there was the early crisis of confidence in the periodic table when the old school physicists and chemists had to grapple with what to do with isotopes of the elements. Having accommodated that, it turns out the periodic law is only an approximation, rather than a Law, as such. That leads into the observation that there is no ideal periodic table, since the table depends on the properties of interest. Hence Tier 5. From the perfection of Tier 1, we descend into the "chaos" of Tier 5.

Thus, an emerging field of thought is the importance of symmetry breaking, rather than pure symmetry:

1. "…symmetries matter, largely because we like to see them broken sometimes: the laws, particles and forces of physics all have their roots in symmetry-breaking. They create what David Gross of the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara, calls the "texture of the world". These considerations have led Florian Goertz at the Max Planck Institute for Particle and Astroparticle Physics in Heidelberg to propose the existence of a new particle that is single-handedly capable of cleaning up five of the stickiest problems in physics. "Complete symmetry is boring," says Goertz. "If symmetry is slightly broken, interesting things can happen." " (Brooks 2018, p. 30)

2. "Through the work of many physicists, the concept of broken symmetry was introduced into elementary particle physics in the 1960s and 1970s. The idea was, in the simplest language, to keep the mathematical forms symmetrical, but the physical consequence unsymmetrical. The standard model, for which Glashow, Salam, and Weinberg shared the Nobel prize in 1979, was based on gauge theory with broken symmetry. It has been extremely successful." (Yang 1996, p. 286)

3. "Physical chemistry is fundamentally asymmetric. How could it not be when the proton weighs so much more than the electron?" (Philip Stewart, pers. comm. 30 Dec 2019).

Evidence of new physics could have been under our noses all along

4. "Many of these remaining problems boil down to one. Crudely phrased, some things are exceptionally small while related things are exceptionally big. This is known as the hierarchy problem, and once you spot it, you start seeing it everywhere.

Take the four fundamental forces of nature. The weakest two are gravity, and the weak nuclear force, which only operates on the tiniest of scales and is responsible for certain types of radioactive decay. The weak force is weak, but compared with it, gravity is some 25 orders of magnitude weaker – a bizarre state of affairs that, as yet, has no good explanation.

The asymmetry reappears elsewhere. Dark energy, the mysterious force that is causing the universe’s expansion to accelerate, is 120 orders of magnitude weaker than we would expect. Dark matter, which is the dominant form of matter in the universe, interacts very weakly with regular matter. Neutrinos, the lightest particles in the standard model, are thousands of times lighter than anything else.

These disparities are profoundly vexing to physicists, who prefer to see related parameters in a theory take broadly consistent values. This preference for "naturalness" drives much theoretical speculation – some would say to a fault. "Nature doesn’t care about our aesthetics," says [Nathaniel] Craig [a theoretical physicist at the University of California, Santa Barbara].

*     *     *

Ten years on, nothing has changed. We were fixated on supersymmetry for too long, says Isabel Garcia at the University of California, Santa Barbara, searching under the convenient street light to the detriment of the field. But the story of the LHC is far from over. The collider has recorded only 3 per cent of the data we expect it to collect in its lifetime, and an upgrade to higher energies in 2020 will further raise its chances of seeing something surprising.

But the LHC's failure to break any new ground has emboldened a new generation to question the hunches that motivated previous searches. "This optimism is most widespread amongst the youth," says Matthew McCullough, a theoretical physicist at CERN. "We've shaken off the cobwebs of the theories handed down by our PhD advisers." " (Eure 2019)

It remains to be seen if the YAPs (young asymmetrical pups) can teach the OSDs (old symmetrical dogs) some new tricks

Even so I consider that (a) asymmetry cannot be appreciated or understood without understanding (b) symmetry, and how and why things go from (b) to (a). See also Hegstrom & Kondepudi (1990), and Rosen (1996).

• Brooks, M.: This one particle could solve five mega-mysteries of physics. New Scientist, 3191, (2018)
• Eure, J. Evidence of new physics could have been under our noses all along. New Scientist, 3217, 16 Feb (2019)
• Hegstrom, R.A., Kondepudi, D.K.: The handedness of the universe. Sci. Am. 62, 108–115 (1990)
• Rosen, J.: Symmetry in science: An introduction to the general theory. Springer, New York (1996)
• Yang, C.N.: Symmetry and physics. Proceedings of the American Philosophical Society. 140, 267–288 (1996)

--- Sandbh (talk) 02:19, 25 July 2020 (UTC)

Four irregularities

Each of the four irregularities namely electrons; neutrons; element properties; and periodic systems has some kind of guided boundary.

This reinforces my impression that all periodic systems have their place under the sun. That is the key learning for students.

Tier 2: Electrons

The Madelung Rule always returns to running true after each wobble (analogous to a gyroscope?).

Tier 3: Neutrons

Their numbers are bounded by the neutron drip line, a subject about which, as yet, I know little.

Boeyens and Levenids (2008, p. 144) write:

"Harkins (1931) discovered a classification of the the stable nuclides in terms of the ratio N/P and showed that this ratio never exceeds the value of 0.62 in atomic species. The same classification was rediscovered independently many years later (Boeyens 2003) and the maximum was shown, more precisely, to be the golden ratio = 0.6180."

• Boeyens, JCA 2003, J. Radioanal. Nucl. Chem., 257, 33
• Boeyens JCA and Levendis DC 2008, Number theory and the periodicity of matter, Springer
• Harkins 1931, Phys. Rev., 38, 1270

Tier 4: Element irregularities

The irregularities in the properties of the elements might possibly be encompassed by the work of Hsueh and Chiang (1937). See appendix 2.

Chemically, the metallic or nonmetallic nature of the elements correlates with, to at least a first order approximation, the four key properties of

• atomic radius
• electron affinity
• ionization energy; and
• electronegativity.

On atomic radius, Peter Atkins (2019) wrote:

"The periodic table and the concept of the elements of education inspires all manner of other thoughts. One is the desert-island thought: if you were asked to identify the central elemental concept summarized by the periodic table which, with you isolated on a conceptual desert island and asked to set about rationalizing chemistry, what would it be? My choice would be atomic radius."

Here.

Godovikov & Hariya (1987) showed a relationship between atomic (orbital) radius and electron affinity:

Here.

Myers (1981) demonstrated a smooth curvilinear relation, for vertical groups in the periodic table, between the electron affinity of an atom and the ionization energy of its neighbour with atomic number larger by one:

Here.

I showed a correlation between EN and radius in my Constellation of electronegativity:

Here.

Thus:

Atomic radius	→	Electron affinity
↑		↓
Electro- negativity	←	Ionization energy

Tier 5: Periodic systems

I hope my periodic system landscape, based on the ideas of Scerri and Schwarz, represents a crude start to showing some semblance of order.

Appendix: Symmetry breaking

Much like a pencil falling to the ground from its tip in a trade-off of symmetry for stability, Davies (2007) writes that the Big Bang could have established a complex but stable universe (or multiverse) from symmetry breaking as the heat radiation in "space" lowered abruptly past the Curie Point.

Here.

Ethan Siegel, an astrophysicist, concludes:

"Our Universe may not be as elegant as we hoped for after all."

Here.

That said, there is a lot of order amongst the disorder. That seems to be the key: pure order = complete stasis; pure disorder = complete chaos. Interesting things happen between the two poles. As the Goldilocks principle goes, "Neither too much nor too little, but just right."

"When Coleridge tried to define beauty, he returned always to one deep thought; beauty, he said, is unity in variety! Science is nothing else than the search to discover unity in the wild variety of nature,—or, more exactly, in the variety of our experience. Poetry, painting, the arts are the same search, in Coleridge’s phrase, for unity in variety."

Bronowski J 2011, Science and human values, Faber & Faber, London

Appendix: Chin-Fang Hsueh and Ming-Chien Chiang

J. Chinese Chem. Soc, 5, 263 (1937). (In English)

I attempted to get a copy of this article via the Australian National Library, and the British Library Lending Service, without success. The Australian National University holds copies of the serial involved, but this particular volume was missing.

The article is cited in Moeller’s Inorganic chemistry (1953, p. 119) in the following passage:

"In an extremely interesting and searching article, Hsueh and Chiang consider any periodic property to consist of two factors, one a periodic factor determining the periodicity and the other an amplitude factor causing numerical change in the property within a given family of elements.

The periodicity factor is, in turn, a function of valency or outermost electronic configuration, and the amplitude factor is a function of energy state and atomic radius.

The periodicity function may be either a maximum at the center of a period or a minimum at the center.

Periodic properties of the increasing class embrace atomic frequency, melting point, boiling point, etc., whereas those of the decreasing class are atomic volume, atomic radius, atomic parachor, etc.

Correspondingly, the amplitude function may amount to either parallel or crossing combination, that is, the amplitudes for the sixteen periodic families may simultaneously increase or decrease or they may change in reverse order for positive and negative elements.

Properties involving parallel combination are such ones as atomic volume, atomic radius, ionic radius, and ionization potentials, whereas those involving crossing combination are such ones as melting point, boiling point, and hardness.

Periodic properties may therefore be classified, according to Hsueh and Chiang, into the four general types: parallel amplitude, increasing periodicity; parallel amplitude, decreasing periodicity; crossing amplitude, increasing periodicity; and crossing amplitude, decreasing periodicity.

By combining periodicity and amplitude functions, Hsueh and Chiang derive a property equation [to follow, Sandbh] from which the numerical magnitude of a property P is related to the atomic number Z of the element in question in terms of valence V, a function of the periodic factor y, the principal quantum number n, and two parameters a and p, which are constants for a given family of elements but different for different families.

By means of this equation and a consideration of the types of periodic properties already mentioned, theoretical variations in properties are evaluated and found to be in reasonably good agreement with observed variations. Certainly curves plotted from theoretical values so calculated against atomic number agree closely with similar ones drawn from measured values."

--- Sandbh (talk) 07:45, 26 July 2020 (UTC)

Defining a metal (chemistry perspective)

Extended content

This is the last reasonable definition we discussed: A metal is an element that has a lustrous appearance when freshly prepared or fractured and (a) has a densely-packed crystalline structure;1 or (b) forms a simple cation in aqueous solution;2 or (c) has a basic oxide. All other elements are nonmetals. 1 Hexagonal-close packed, face-centred cubic, α-lanthanum, α-samarium, body-centred tetragonal, or body-centred cubic 2 Including aqua-cations such as [Bi(OH2)8]3+ It's modelled after the IUPAC defintion of a hydrogen bond. The two physical and two chemical properties involved are mentioned in the literature as being characteristic of metals. I draw a distinction here from e.g. an astronomy-based definition of a metal: "Hydrogen and helium are nonmetals; elements having Z > 2 are metals. Sandbh (talk) 05:21, 24 July 2020 (UTC) I have some thoughts but they will wait till I am sure they satisfy the standards I believe are relevant. So I just note that antimony seems to satisfy your definition as calculations suggest it does form an aqueous cation. Double sharp (talk) 07:08, 24 July 2020 (UTC) ​I don't count [Sb(H2O)4(OH)2]+ as a simple cation. Sandbh (talk) 07:15, 24 July 2020 (UTC) @Sandbh: The unhydrolysed version [Sb(H2O)]~8]3+ also exists according to calculations. See 10.1016/j.cplett.2011.05.060 and 10.1021/ic901737y. Of course, first and second hydration spheres are strongly distorted, but that's exactly also the case for indium and tin aqua cations. Double sharp (talk) 07:22, 24 July 2020 (UTC) ​I'll amend the definition to say: "…forms a simple cation,2 of significant concentration,3 in aqueous solution;" 3 Greater than trace level, in ambient conditions, within a normal pH range (0–14) --- Sandbh (talk) 07:45, 24 July 2020 (UTC) @Sandbh: OK, now it gives what I think you want. I will still work on finding one I like more though. ;) Double sharp (talk) 08:01, 24 July 2020 (UTC) I look forward to it. Here it is completed then: A metal is an element that has a lustrous appearance when freshly prepared or fractured and (a) has a densely-packed crystalline structure;1 or (b) forms a simple cation,2 in aqueous solution;3 or (c) has a basic oxide. All other elements are nonmetals. 1 Hexagonal-close packed, face-centred cubic, α-lanthanum, α-samarium, body-centred tetragonal, or body-centred cubic 2 Including aqua-cations such as [Bi(OH2)8]3+ 3 Of a concentration greater than trace level, in ambient conditions, within a normal pH range (0–14) @Sandbh: Turns out, it is not hard to resolve to my taste. So here is my view. This is not a chemical question, but a physical one, because it is about properties of simple substances rather than elements. We can talk about metallicity of NaK or lack thereof for NaCl just as one can for Na or Ge, it is about the bonding. But for NaK or NaCl they are not elements, it doesn't just relate to one element's chemistry. The reason why it shows correlation with chemical behaviour for an element is because they both stem from the electronic structure giving the band structure, but again you can see differences. Germanium has an aqua cation (10.1002/jcc.21315; meanwhile this is super dependent on water as the solvent, if you change it iodine can have a cation as well) but is a semiconductor, tungsten is a metal but has no aqua cation. Close packing is structural, it's something similar to explain packing of Mn or Cu or Na or Sb vs packing of CsCl or NaCl or CuCl. So I don't consider most of these criteria relevant, they just show correlation because similar things drives both physical metallicity and chemical properties and thus creates chemical metallicity stereotypes. So I'd teach metals by the physical definition, and then say that because of what drives those physical properties to happen, they often share some chemical properties, but they're just tendencies with many many exceptions because that's not a defining criterion. Therefore, I revert to the old Droog Andrey criterion based on the solid state physicists. Just one criterion will do. All elements that are metallic or semimetallic as simple substances, in all stable enough forms at STP, can be called metals as they have the important thing which is binding by a delocalised electron cloud. Re borderline elements: Alpha-tin is a semimetal, so no problem there. (The grey tin formed from the phase transition is amorphous.) It has a Fermi surface. Of course beta-tin presents no problems whatsoever. Germanium is a semiconductor, so not a metal. No need to worry about beta-germanium, that needs 120 kbar. At high enough pressure everybody is a metal, but that's not the important thing. That takes care of all other metalloids too. Carbon doesn't count as a metal even though graphite is a semimetal. Diamonds are forever after all, that surely meets the criterion for "stable enough". ;) Antimony is a metal, as the yellow and black allotropes are unstable. Light turns the yellow allotrope back into the metallic one, even at 0°C the black one turns into metallic antimony, see Holleman & Wiberg p. 758. That has to do with the large size of Sb atom. Arsenic is not, because black arsenic doesn't conduct electricity, yet needs 270°C for the conversion to gray arsenic to start, see Holleman & Wiberg p. 743. As oganesson is bigger than tin I am in agreement with DA: intuitively, it seems more likely to be a (semi)metal. Copernicium just seems weird. So we wait for more predictions on period VII. As such I feel this is only just one property that contributes to periodicity among many. Therefore, I restore the colouring of blocks as primary on my userpage. This is just for there for now of course. You may disagree, of course. Double sharp (talk) 10:14, 26 July 2020 (UTC) ​The reference you gave for Ge2+ (aq) is a theoretical study. AFAIK there remains no empirical evidence for such a cation. Sandbh (talk) 13:03, 26 July 2020 (UTC) @Sandbh: It's good enough for me. Wulfsberg's generalisations imply this should have similar acidity to an average +3 d block ion, so it will not be impossible just from that. I suspect it is simply not known for sure because of (1) Ge being unstable in +2 state (it only stays there a while due to kinetic effects) and (2) maybe too ready complexation by other anions. As Droog Andrey suggested before, it could be tested for Ge2+ and Sb3+ and other doubtful transition metal cations with weakly complexing perchlorate or fluorocarboranate anions. Maybe it is interesting to find out for other reasons. But I think not for this classification, it is biased towards water. With different solvating ligands you may get iodine or phosphorus as cations. Again, you may disagree if you want. Double sharp (talk) 13:25, 26 July 2020 (UTC) ​From a chemistry perspective, the definition of a metal being something having a Fermi surface etc is too simple an answer to a complicated problem. As well, from chemistry-based perspective, I suggest a definition that includes some chemistry-based behaviour would be more appropriate. Your application of the Fermi surface definition is problematic. The most stable form of carbon is graphite, a semimetal. The most stable form of arsenic is the semi-metal form. The question of the status of amorphous grey tin remains outstanding. Packing efficiency is, I suggest, related to the Goldhammer-Herzfeld metallisation catastrophe. More specifically, the Goldhammer-Herzfeld criterion is the ratio of the force holding an individual atom's valence electrons in place with the forces on the same electrons from interactions between the atoms in the solid or liquid element. When the interatomic forces are greater than, or equal to, the atomic force, valence electron itinerancy is indicated and metallic behaviour is predicted. Otherwise nonmetallic behaviour is anticipated. It is a simple measure of how metallic an element is, the recognised metalloids having ratios from around 0.85 to 1.1 and averaging 1.0. As the ratio is based on classical arguments it does not accommodate the finding that polonium, which has a value of ~0.95, adopts a metallic (rather than covalent) crystalline structure, on relativistic grounds. Even so it offers a first order rationalization for the occurrence of metallic character amongst the elements. Sandbh (talk) 13:37, 26 July 2020 (UTC) @Sandbh: You may have your opinion. I'm satisfied with how I handled carbon and arsenic in my original posting (anything metastable enough to persist at room temperature without obvious spontaneous transformation is good enough), and because it seems from the previous discussion that we start from too different premises on most things, I think a debate on those two will not be fruitful and will end up just generating more heat than light. As for tin, I do not know what "amorphous grey tin" might mean anyway because "amorphous" means "lacking crystalline structure", so I do not know what the difference between "amorphous grey tin" and "amorphous white tin" would be. Maybe I am wrong about that, in which case I would like a reference or two. Double sharp (talk) 13:41, 26 July 2020 (UTC) @Double sharp: There's nothing you need to change. The Fermi-surface definition, based on the behaviour of the elements at absolute zero, is a physics-based definition. What physicists refer to as metals is not the same as what chemists refer to as metals, as our metal article makes clear. Sandbh (talk) 14:06, 26 July 2020 (UTC) @Sandbh: Well, there you have it; I prefer the physics-based definition as metallicity or not is a property that can be applied to compounds, not just simple substances. You will find it in NaK just as surely as in Na or K. Whereas chemistry-based definitions are about properties of the elements, that's something different. Similar things give rise to both, that's why there are strong parallels, but as you can see they are not perfectly correlated (e.g. rhenium passes your physics criteria, fails your chemistry criteria). When an element gives rise to multiple simple substances (allotropes), I simply say that all allotropes metastable at room temperature must at least have Fermi surfaces: that's both a reasonable extrapolation of the physics-based idea and gives a metal-nonmetal boundary that chemists would also probably find not bad (metals Li-Be, Na-Al, K-Ga, Rb-Sb, Cs-At, Fr-Og maybe minus Cn and Og awaiting predictions). They may remove antimony if they wish as its chemistry has about equal relations to stereotype behaviour of metals and stereotype behaviour of nonmetals, and not being physically a real metal, I have considered it, but then as DA helpfully reminded me beryllium becomes a problem as it's not a true metal physically either (10.1103/PhysRevB.100.045145) and is also pretty weak chemically. So I decide to keep antimony there. Double sharp (talk) 14:14, 26 July 2020 (UTC) @Double sharp: Jones notes that in classification science, categories are usually defined by more than two attributes. In this context, I had in mind the following working definition for you: "An element is categorised as a metal if, in all of its crystallised bulk forms at or near ambient conditions, it has Fermi surface. Carbon and arsenic are precluded from this definition since they have stable semi-conducting allotropes (carbon as, for example, C60, and arsenic as arsenolamprite)." I read the article on Be and saw nothing specifically there saying it's not a "true" metal, whatever that means. They observe Be is a nodal-line topological semimetal. 10.1103/PhysRevLett.117.096401 say Mg, Ca, and Sr also harbor Dirac Nodal Lines and speculate that the topological property of the DNL might naturally exist in other elemental metals as well. This appears to be scope creep to the point of verging on something less than useful, categorically speaking. Harrington (1946) referred to the true metals as being in groups 1 to 11. Klemm (1950) divided the elements into true metals, meta-metals, half-metals, and nonmetals. True metals were the alkali metals, the alkaline earth metals (excl. Be), the group 11 metals, and Al. Klemm counted Be as a meta-metal along with the group 12 and remaining group 13 metals, and beta-Sn, and Pb. Russell and Lee (2005, p. 158) more simply observe, as follows: "The cause of Be's low ductility is its proximity to the nonmetallic elements in the upper right corner of the periodic table, which results in mixed metallic and covalent bonding. In HCP Be bonding within the (0001) basal plane is metallic, but bonding between (0001) planes is partly metallic and partly covalent. This causes large differences in the critical resolved shear stresses among Be's three active slip systems and gives Be the lowest c/a ratio (1.56%) of any HCP element. The Poisson ratio of Be is only 0.02, much lower than the 0.25 to 0.40 Poisson ratios of most metals." --- Sandbh (talk) 00:42, 27 July 2020 (UTC) @Sandbh: Well, that does eliminate some difficulties regarding checking amorphised forms of everybody (which is maybe hard to find in some cases), so yes, this does seem like a useful simplification. It excludes red phosphorus, but that will be a nonmetal no matter what anyway. "True" metal means as opposed to being a semimetal. I agree that this is not a useful distinction for these purposes because the important thing is the delocalisation and they have both. Beryllium is just an illustration of why it doesn't seem useful. Antimony It is also why I continue to regard antimony as a metal. It is just too much trouble to exclude it. If one worries that it is a semimetal – then beryllium is in trouble (and not for very useful reasons). If one worries that its structure is not close packed and has only six nearest neighbours – then polonium is in trouble (and again not for what seem like very useful reasons). If one worries that it forms no aqueous cation or basic oxide – then rhenium is in trouble. If one worries that it has the unstable forms that are not metallic – well they spontaneously convert to the metallic form at standard conditions already, so they're hardly representative, and considering unrepresentative forms opens Pandora's box for me. So I prefer to leave it in because all the simple ways to exclude it give unwanted consequences, anything else is likely too complex, and I don't feel the gains are justified. Will the chemists complain in droves if antimony is regarded as a metal on physical grounds? I don't think so. I guess most chemists who don't use a "metalloid" category already do that. And besides antimony is noticeably more metallic than the other bunch of metalloids even if it is less so than bismuth. So simplest sufficient complexity in the form I prefer to apply it favours leaving Sb in AFAICS. That is if we start from my premise that this is a question more usefully answered from the physical perspective and simple substances. You may disagree based on the history, but you know I prefer to ignore the history when coming up with the classifications and just ask how we would do it if starting afresh now. Usually the result I get from that is "something quite like the history but maybe with a few points of minor difference", which seems reasonable to me: in the past they saw the same thing, so only minor differences (small enough that inertia sets in and people don't feel a need to change it as the theory doesn't go quite deep enough) will be observed. You saw it in my approach to the periodic table with He and Lu/Lr, you see it again now in metallicity with Sb. ;) P.S. From Metallium you can see how many elements look as rods. Unfortunately not all the key region is seen, but you can see how silicon and germanium do not have the metallic lustre of the preceding element, but a glassy mirror-like one. Antimony and bismuth have the metallic lustre. Tellurium has no rod listed, but it does look more glassy like selenium. Arsenic is not very clear in the sample though. For the other useful link: their element series coins (and descriptions). Apparently, bismuth and antimony despite being brittle do not shatter upon striking coins. Arsenic is not mentioned but also not offered for sale yet, so I presume the obvious approach fails to work. Tellurium was offered, but from hot-pressing instead. Double sharp (talk) 04:22, 27 July 2020 (UTC) @Double sharp:Yes, it doesn't matter about antimony. It's fine to regard it as a metal, just as it's fine to put Lu in group 3, as long as the context is explained to readers, colleagues, and students. Then one can sit back and appreciate the perspective that this context offers and, if appropriate, compare it with other contexts, e.g. the one that treats the metalloids as the semimetals + semiconductors = B, C, Si, P, Ge, As, Se, Sb, Te, I, Bi. It'd be useful to have good responses up one's sleeve to the following observations: "When non-metallic elements react with the oxidizing acids, acidic oxides or acids are formed… The trisulphides of arsenic and antimony are acidic, forming salts with yellow ammonium sulphide and alkali, while that of bismuth is typical of a metal." (Moody 1969, pp. 267, 321) "Interest centres on the trend from non-metallic to metallic properties with increasing atomic weight. Thus there are many parallels between phosphorus and arsenic, but considerably fewer between phosphorus and bismuth, which is a typical B metal like tin or lead. Arsenic and antimony are important largely because of their intermediate or metalloid character…" (Smith 1973, p. 547) "All the elements react readily with halogens but are unaffected by nonoxidising acids. Nitric acid gives, respectively, phosphoric acid, arsenic acid, antimony trioxide, and bismuth nitrate, which well illustrates the increasing metallic character as the group is descended." (Cotton & Wilkinson 1976, p. 288) "In the nitrogen family, we move from nonmetals that form acidic oxides—nitrogen and phosphorus—to metalloids that form amphoteric oxides—arsenic and antimony—to the last element—bismuth—that is barely a metal and forms a basic oxide." (Brady & Holum 1996, p. 61) "Antimony is found in forms analogous to those of arsenic… The most common antimony chalcogenide ore is stibinite (antimonite), Sb2S3… Some metal antimonides are breithauptite = NiSb… and dyscrasite (antimony silver) = Ag3Sb… Bismuth is not found in large amounts in nature… Unlike arsenic and antimony, it is not found as anionic bismuthides." (Wiberg 2001, p. 757) "Bismuth(III) oxide occurs naturally as bismite and is formed when Bi combines with O2 on heating. In contrast to earlier members of group 15, molecular species are not observed for Bi2O3 and the structure is more like that of a typical metal oxide.’ (Housecroft & Sharpe 2008, p. 474) --- Sandbh (talk) 04:59, 27 July 2020 (UTC) @Double sharp: For you consideration, Yb is a topological semimetal, as well as the alkaline earths. There is nothing to worry about the fact that Sb is a semimetal, so too is Bi. The tricky part is that there are too many "ands" for apparent comfort, unlike Po which forms a cation in aqueous solution, unlike rhenium, which is close packed. Thus, in support of Sb as a metalloid: brittle semimetal semiconducting allotrope low packing efficiency (41%) only six nearest neighbours (3+3) intermediate IE intermediate EN abnormally high heat of fusion (19.79 kj/mol) compared to 14.5 average for close-packed metals intermediate thermal conductivity 24.3 W m−1 K−1 predominately nonmetallic chemistry no simple cation in aqueous solution no basic oxide Sb2O3 is polymeric, amphoteric, and a glass former GH-ratio near unity In support of Sb as a metal: relatively high reflectivity: Si 41%; Ge 35%; As 46%; Sb 70%; Te 59%. fair electrical conductor; the liquid form is a metallic conductor; it can form alloys with one or more metals such as aluminium, iron, nickel, copper, zinc, tin, lead, and bismuth; displaces hydrogen from water, when heated the otherwise acidic pentoxide Sb2O5 shows some basic (metallic) behaviour in that it can be dissolved in very acidic solutions, with the formation of the oxycation "SbO+ 2" the compound Sb8(GaCl4)2, which contains the homopolycation, Sb82+, was prepared in 2004. No need for a debate, nor do I have an expectation of one. Sandbh (talk) 07:25, 27 July 2020 (UTC) Lu + metallicity @Sandbh: Two parts to this post. First one is about group 3 (since you mention Lu in group 3 as contextual), and second one is about metallicity. I say things calmly (I think, if not you can scold me and tell me what to change) about group 3 because the approaches I take for both subjects seem parallel. You may skip that part or ask me to delete it if you feel it is off topic, I just wanted to draw the parallels. So let's start. It's not a debate, just a description of how I see both things. Lu: Contextual or universal I view Lu in group 3 as not contextual, rather I consider it universally applicable. However I also consider universally applicable the secondaries not explicitly shown by it, like Sc-Y-La and B-Al-Sc. Sc-Y-La is a valid linkage, it is totally valid secondary periodicity and useful in any context. And, so is B-Al-Sc, so is C-Si-Ti, so is He-Ne, so is H-F, so is even Ti-Zr-Ce. The working chemist should be aware of all of those and then some, no matter which field he is in. It's not just that some are more useful in this field, some in that field; they are actually all useful in all fields of chemistry. The continued popularity of the 8 column form in Russia (with B, Al, Sc all in one column) speaks to that. Why I favour He-Be + Sc-Y-Lu is for reasons of pedagogy and consistency in requirements. It is quite easy to teach (let us say, not harder than standard He-Ne + Sc-Y-La), and avoids awkward questions from the back of the classroom about why Sc-Y-La is considered important enough to reflect as primary periodicity but not, say, B-Al-Sc, or why He-Ne is important enough but not H-F (just think of physical properties for that one). And the reason why I have to avoid such questions is because of my rejection of gas-phase ground-state configurations and condensed-phase configurations (that's why I don't appeal to electron configurations to remove B-Al-Sc from consideration, because after all there are legitimate similarities and it's something useful for chemists to know). Because to my taste, those configurations are drilling down too deeply to something that will not be useful until the students reach a rather advanced level of chemistry. One can ask students to memorise the gas-phase exceptions (I did memorise them), but then they cannot use them to predict much outside some very specialised topics that occur very late and that most will not go on to, so then it feels like I'd be asking them for something that they'll probably never use. And it is hard to ask for memorising condensed-phase configurations, when solid state physics is generally not part of the high-school chemistry syllabus, when there are just fractions of many configurations added together, and the energy differences are so low that configuration may be impacted by turning on the lights (visible-light photons are enough). These two will be important for too few things for the first-year students getting a periodic table, I find. And I want to be able to start the g block without getting a migraine painstakingly characterising a bear that looks like it wants lunch by some hard-to-observe property to borrow your analogy. And I think that's important because the kids need to get some wonder about how things are still being discovered, so when these elements appear I still think they should go (and they probably will go) on everyone's periodic tables. But you see, calculations already cannot yet determine lowest-energy configuration for single atom of element 123, and anyway in many such early g elements we have a bunch of electron configurations that are extremely extremely close in energy (sometimes there is really even no definite ground state, just fractions of one configuration plus fractions of another). I just don't want to deal with all this complexity. It's good enough for almost all purposes to just look at how many valence electrons there are and which orbitals are valence orbitals to determine blocks, without actually going further and asking for an exact configuration. I guess it can be called simplest sufficient complexity. And the result isn't even bad. Lutetium is not further from scandium and yttrium than lanthanum, and helium over beryllium gives hydrogen over lithium a partner (and some understanding of kainosymmetry too for later; this way, no one has to unlearn stuff if they do choose to go deeper), so the table is sound enough for vigorous use both by beginners and by expert chemists. Of course, one can add criteria to make current standard He-Ne + Sc-Y-La come out as the result, but again: do I think adding some more complexity in teaching the criteria for element placement is going to be worth the added benefits this might give? I think, to my taste, not really. And remember that I do ask to keep in mind that secondary periodicity exists and comes from having the same number of electrons above or below a noble gas configuration. So we don't lose sight of Sc-Y-La (all three electrons over a noble gas core). We also don't lose sight of B-Al-Sc (same), C-Si-Ti (all four electrons above), P-V, S-Cr, Cl-Mn (same idea, five, six, or seven electrons), d elements to actinides (Y-Ac, Zr-Th, Nb-Pa, Mo-U), and of course He-Ne (all noble gas cores), H-F (both one electron short), and Be-Mg-Zn (all six electrons away from a noble gas core) and Ca-Sr-Yb (all sixteen electrons away from a noble gas core). Even stuff like Pt to chalcogens or Au to halogens are not neglected because I would mention that Hg has relativistically induced properties of a noble gas (so, same thing probably happens for Rg with halogenic properties and Nh as very two-faced like astatine). So all important linkages are covered, they will help all chemists. And definitely, when discussing group 3, don't just cover Sc-Y-Lu-Lr, also please include not just La-Ac but also Al (maybe even boron to some degree) for comparison. That's why I feel it should be good for real chemists: I favour showing Sc-Y-Lu, but also teaching how to get this sort of thing to generally get not just Sc-Y-La but all those other things that are helpful like B-Al-Sc and C-Si-Ti. Those are all fine, and I ask to keep them in mind. But I just treat the one from valence orbitals as primary for actually drawing. Because it is good enough, and based on very few criteria (two seem to do: one about valence electrons, and one saying that if subshells happen to get drowned within a block, then just treat them consistently as valent or non-valent when counting valence electrons). It is also very easy to motivate, teach, predict from, and use to classify future elements that we hope should come this decade, without having to do too much work. I don't want to teach multiple forms when I can take one that is very good in itself and just supplement it with secondary periodicity readings to get almost the same thing. And I don't want to have to restrict any generalisations because I want to take the simplest possible thing (so, start with very few things to remember) that will let you guess properties of almost everything quite well to build intuition. So, for me I just want to teach things that work everywhere. Local stuff that works only in some places is fine, but only later when they drill down to the part of the table they want to carve out for themselves. @Double sharp:What you have set out above is a considered approach to your preference for HeBe and Lu in group 3. Is there a condensed description for this interest dependence context e.g. "the periodic table in the context of valence orbitals" or something like that? Sandbh (talk) 00:10, 28 July 2020 (UTC) @Sandbh: You can call it that as a premise, that is a good name for it. I simply think it's so particularly useful as a premise (because of valence orbitals being key to chemistry) that it is worth making universal, as you know. We will not lose the secondary relationships by doing so, as we know how to read them off (same distance from either side of the table but different columns). Just some examples below courtesy of DA. Of course, you can already read those off even without the parentheses as I said above. I just think this is a far more universal premise than any other. In chemistry valence orbitals are ubiquitous in their importance. Ground state electron configuration is only important for some very specialised topics involving gas phase atoms (we have discussed that, that is what I understand from reliable sources, if you want you may disagree), and then you will want to show the anomalies like Cr and Cu as well, not only La and Ac. So, that's why I don't think there are very many contexts in which He-Ne + Sc-Y-La is important. My opinion: why just those two secondary periodicities? Maybe He-Ne is exceptional, but if Sc-Y-La is important, then probably B-Al-Sc or Be-Mg-Zn cries out for some attention too. That's how I think. Again you are free to disagree. Double sharp (talk) 03:28, 28 July 2020 (UTC) Metallicity So, how do I deal with metallicity? I guess the answer comes from how I would respond to your observations. I would not really lose sleep over the fact that Sb has some significant chemical properties that are more characteristic of the nonmetals, because otherwise the situation becomes a bit awkward for the more electronegative metals that favour higher oxidation states. If we demand basic oxides, or formation of oxoacid salts, then questions will arise about niobium or tantalum which have neither. If we complain about antimonides, then we face the problem that polonium is found in nature as polonides (Po decays to Pb, ergo lead polonide appears in nature). If we complain about reactions with nitric acid, then questions arise about tin, because while dilute nitric acid forms tin nitrate, concentrated nitric acid produces stannic acid. If we complain about molecular species for oxides, then questions arise about rhenium or osmium in high oxidation states when they are at their most electronegative. In particular, Sn seems also dangerously close to the border. The stable state at STP of 0°C is a semimetal (can even be called a zero band-gap semiconductor) that has only four nearest neighbours (conversion of beta to alpha form will already happen), it has no basic oxide, and its simple cation is badly hydrolysed (you won't find a more hydrolysed +2 cation except maybe uncertain germanium). Meanwhile it will become a bit difficult to classify even the already known superheavy elements even provisionally from predictions because there are a lot of things to think about and we don't even have all properties predicted yet (crystal structure predictions are still not around for Mc, Lv, and Ts, and I am not aware of any predictions about the aqua cations of elements past Rf). So, again: I do not want to have to deal with this complexity, it's starting to become a similar problem to the above issues for electron configurations. I do not want to force the students to memorise a lot of different things for different parts of the table (especially because, well, how many chemists actually focus on the whole table in their work?), when a single generalisation could get almost everything across and draw a simple line that they can use. They can drill down later when they decide where in the table they will make their home. But for beginners I prefer stuff that generalises everywhere, as it will be the most useful to start from. So I apply the same principle as I did to group 3 to resolve metallicity for my taste with basically two criteria (one about Fermi surfaces, one about stable allotropes). And that will immediately let me say provisionally that the whole 7th period may just as well be called metals (except maybe copernicium, 6d expansion appears not to be enough) due to big atomic radii, and probably the whole 8th period is metallised for the same reason except element 172 because of closed-shell (probably a dispersion-force solid or liquid like a tri-xenon). I do not want to complicate the definition with details to kick out antimony, when the result of the very simple definition looks good enough. Antimony is very weak as a metal, yes, but maybe the logical endpoint after tin and bismuth's steps towards nonmetallicity (all other metalloids are more nonmetallic). And it does not look totally out of place. DA mentioned that in Russian textbooks Sb is often treated as a metal (there are no metalloids), and I doubt anyone complains much. As a parallel to secondary periodicity I of course would teach that near the borderline elements will have some echoes of the other side, and then happily go along adding elements on the wrong side when describing "the nonmetals" (where I would always try to include at least tin, astatine, polonium, bismuth, maybe even lead for comparison) as well as "the metals" (where I would probably include for comparison all typically recognised metalloids plus selenium). Silicon and germanium conduct electricity like metals when melted, antimony stays metallic, but arsenic loses metallic conductivity. Tin, antimony, and bismuth all have significant nonmetal-like chemical properties, so do many transition metals in high oxidation states. Some metal-like chemistry is observed with germanium in the lower oxidation state +2. All of that is useful to know too. For comparisons, therefore, elements coming out a little to the wrong side can be included, but the usual line I draw remains useful enough for most work and not complex to motivate. So I take simplest sufficient complexity and say "well, Sb and only Sb added from metalloids to metals is not so bad I want to lose sleep over it". There's no need to have lots and lots of different metal-nonmetal lines when we can just draw one and say "of course, keep in mind that elements near the line can have both characters". That's again my parallel to secondary periodicity; yes, a good chemist must keep relationship of B-Al-Sc-Y-La in mind, just as a good chemist should not let a metal-nonmetal difference blind him to similarities like As-Sb-Bi, the nonmetallic properties of Sb, or the metallic properties of Ge. But again: a short and simple definition and line is always there for you to start from and treat as primary for teaching and showing. So, for me: is Sb as a metal universally applicable? Yes, I would say it is, because it's useful to keep in mind, and is sound enough as a classification for vigorous use by both beginners and expert chemists. So, of course, is Sb as a nonmetal: all chemists seriously working with it must be aware of both sides of the coin. And a book on elements split into metals and nonmetals would do very well covering Sb in both parts. I simply put the former as primary because it makes the definition less complicated. You can see that what I do here is basically parallel to how I handle group 3. Again, that's all my view, I simply describe it, hopefully calmly. You may disagree if you want. Double sharp (talk) 10:18, 27 July 2020 (UTC) @Double sharp: This is all good except I don't understand what the simple line is. Is it the useful simplification I suggested? Tin, being ductile and forming a simple cation (aq.), is a distraction, so to speak. I suggest another distraction is STP (0 °C 100 kPa). Not much aqueous chemistry will occur in ice. More meaningful is SATP (25 °C 100 kPa). Compare with the NTP of NIST: 20 °C, absolute pressure of 1 atm (14.696 psi, 101.325 kPa). Sandbh (talk) 00:31, 28 July 2020 (UTC) The simple line @Sandbh: Yes, it is your suggested improvement to my definition (still including antimony). So my metal-nonmetal line cuts off H from Li, He from Be in the s block; and then within each period of the p block it goes between Be and B; Al and Si; Ga and Ge; Sb and Te; At and Rn. I don't yet really know where it'll be in the seventh period, so I wait for more predictions. (I cannot believe oganesson as a semiconductor, intuition revolts and says that if it's larger than tin in terms of atomic radius it should get metallised; as for copernicium, well, all depends on how active 6d orbitals turn out to be.) Tin pest just worries me because the transition can still start above freezing point of water. Regarding Sn2+: be careful of this cation. ;) Coordination number is small, the metal cation is very acidic, because lone pair is polarising and water molecules are forced into positions where they easily lose protons (same problem as Sb3+), see 10.1021/ja039248p. Actually aquated Sn2+ is not even known in the gas phase, it seems to exist in condensed phase only due to thermal motion of water molecules. Same problem happens with Pb2+, so likely also with Bi3+. Double sharp (talk) 03:59, 28 July 2020 (UTC) @Double sharp: I'm OK with Sn2+. I can see it on the E-pH diagram, within pH 0–1, straddling either side of 0.0 E(volts). Even as grey tin it still has a Fermi surface, since it's a zero-gap semimetal. Sandbh (talk) 07:13, 28 July 2020 (UTC) @Sandbh: And is Sn4+ also on those E-pH diagrams? Double sharp (talk) 07:16, 28 July 2020 (UTC) @Double sharp: Yes, it is. pH <= −0.5; 0.25–3.0 V. PS: Chemically, grey tin falls marginally on the metal side of the line given tin is ordinarily regarded as chemically weak metal rather than a chemically weak nonmetal. Sandbh (talk) 07:21, 28 July 2020 (UTC) @Sandbh: And does that seem convincing to you considering that it surely must be more acidic than Zr4+ by Fajans' rules? It doesn't to me, but maybe you disagree. Double sharp (talk) 07:25, 28 July 2020 (UTC) @Double sharp: You’ll have to elaborate what it is that is supposed to be convincing, or not. Sandbh (talk) 11:22, 28 July 2020 (UTC) @Sandbh: The presence of Sn4+ on the E-pH diagrams. Double sharp (talk) 11:26, 28 July 2020 (UTC) @Double sharp: I see the same patterns in the Atlas of Electrochemical Equilibria in Aqueous Solutions. The Pourbaix authors refer to, "The ion Zr++++, which has been identified only in concentrated solutions of very low pH". The tin authors don't say anything notable (that I could understand) about Sn++++. Parish says of the 4d- and 5d- metals (Zr to Cd; Hf to Hg) that most redox potential data refer to complexes rather than aquated species (p. 133). The most important species in acidic solution is the tetrameric cation, Zr4(OH)88+. There is no evidence for mononuclear species, and the 'zirconyl' ion, ZrO2+, seems definitely to have been disproved. (p. 135). Lidin (1996) says Zr forms no aqua-cations; Sn forms the Sn2+ cation in a highly acidic medium in the form of the complex [Sn(H2O)3]2+. He includes Sc and Y in the chapter on the 4f metals. He says the 4f metals have a very simple chemistry since with but few exception only one oxidation state is displayed, viz. +3. In this respect they resemble the s-block elements, and indeed there are pronounced similarities to Ca, which often occurs in Ln minerals, and to Sr and Ba, particularly in the complicated solid-state structures found. (p. 143). Parish goes on to say of the 4d- and 5d- metals that, "all the compounds show considerable covalency, and descriptions in terms of the ionic model are likely to be rather inaccurate." (p. 137) --- Sandbh (talk) 13:56, 28 July 2020 (UTC) @Sandbh: Basically, I cannot believe it myself because Sn4+ has about equal size to Zr4+, and Sn is more electronegative than Zr. For simple reason of Fajans' rules it has to be more polarising, so it does not make sense that there would exist Sn4+ but not Zr4+. Recent calculations and experiments support what I say here. In perchloric acid medium, if concentration of Zr is kept low (to avoid tetramerisation) and [H+] kept high (1-2 M), you will get [Zr(H2O)8]4+. In review of aqueous metal cations (10.1351/PAC-CON-09-10-22), both [Zr(H2O)8]4+ and [Hf(H2O)8]4+ were included (along with Th, U, Np, Pu +4 cations): and this even when Sb3+ is excluded from metals: of course it is mentioned that they are prone to hydrolysis and tetramerisation. From the paper doing calculations (also on Sb), it appears we indeed have experimental evidence for Zr and Hf cations as we do for Ce and U (just make pH low). That's a far cry from what they calculate for Ge4+, Sn4+, and Pb4+ (hydrolysis within picoseconds). As for covalency: that is, as we have discussed already at great length, just oxidation states. You will find more ionic character if you take electronegative anions and force the metals into low oxidation states. Zirconium and hafnium have very simple main-group-like chemistry too, as with few exceptions only +4 is displayed. Same story for niobium and tantalum with +5. Greenwood and Earnshaw say it. "Lower oxidation states are rather sparsely represented for Zr and Hf" (p. 958), "most of the chemistries of niobium and tantalum are confined to the group oxidation state of +5" (p. 979). In 4d and 5d metals, real transition properties only start strongly at molybdenum and tungsten with cluster compounds in lower oxidation states. We have gone over this. If you want to disagree, that's fine. Double sharp (talk) 14:23, 28 July 2020 (UTC) @Double sharp: I have no concerns wrt to Zr, Hf, and Sn cations. On covalency and oxidation states, Parish writes wrt the 4d- and 5d- series (excl. group 3), "In their compounds a wide range of oxidation states is shown, but all are characterised by the formation of bonds of high covalent character, and there are no simple ionic compounds. Only in a few cases are even simple aquated cations known, other ligands, often anions, being bound in preference to water." (p. 112) The very simple main-group-like chemistry of Zr and Hf is more like the very covalent chemistry of the p-metals. Thus, Parish writes: "The most striking aspect of the chemistry of the p-block metals is the pronounced tendency to covalency." (p. 192) In her entry for Zr, Rossotti writes, "As we shall find with other members of the 2nd and 3rd transition series, simply hydrated cations are fairly scarce." (p. 337) On Hf, she writes, "between La and Hf come the fourteen 4f elements…this Ln contraction has repercussions beyond the 4f series and one of its effects is that the elements of the 3rd transition series…have (except for La) radii that are very similar to those with the same value of n in the second transition series…" (p. 461) Talbot and Talbot (2019, p. 336), in Corrosion Science and Technology, 3rd ed., write, "The only important oxidation states are Zr(IV) and Hf(IV). The charge density that would result from removing all four valence electrons is so high that compounds of Zr(IV) and Hf(IV) are mainly covalent." On Sc, Rossotti writes, "Its chemistry is largely, but not entirely that of the Sc3+ cation"; for Y, "…behaves very much like Sc"; for La, "…forms predominately ionic compounds"; for Ac, "…might also be expected to resemble La as the launch pad element for a series of successors with increasingly filled f orbitals." I do like the phrasing Rossotti uses viz. "repercussions beyond the 4f series", and "launch pad element". PS: Rossotti notes ScH2 is a metallic conductor and asks if it can be Sc3+.2H− with a free electron in the conduction band. That is how Wiberg formulates it. On CsScCl3 she asks if it does really contain ScII. --- Sandbh (talk) 02:07, 29 July 2020 (UTC) @Sandbh: We have gone over this, with sources, and going over it again will not be helpful. So I stop here rather than argue. Thank you for the suggestion for the definition, I have put in something like it on my page, but I continue to regard Zr-Hf and Nb-Ta as s-like pre-transition, just modified for higher oxidation states. Not so much difference between them and Th and Pa, really. Double sharp (talk) 02:36, 29 July 2020 (UTC) @Double sharp: That's fine. It's all water under the bridge, or food for thought (or not). Sandbh (talk) 06:23, 29 July 2020 (UTC) Antimony P.S. Chemically speaking, when a "metalloids" category is not used, Sb usually goes to the metals (that's standard with Russian textbooks). Double sharp (talk) 07:37, 28 July 2020 (UTC) That’s fine as long as they explain the context for so doing, given Sb has a predominately non-metallic chemistry. And how do they treat As? For what it is worth, I have a Russian textbook, General Chemistry, 3rd ed., by N.L. Glinka, Mir Publishers, Moscow, 1980, English translation. Glinka says N-Bi are characterised as a whole as non-metals. Antimony has nonmetallic and metallic properties to an equal extent, and in Bi the metallic properties predominate over the non-metallic ones. (Vol. 2, pp. 66–67). [He treats Group 3 as Sc-Y-La-Ac.] Sandbh (talk) 11:22, 28 July 2020 (UTC) @Sandbh: I don't know, I got the info about Sb from DA. Probably As is a nonmetal following staircase (which he said is usually drawn) and as he said serious sources there call Ge one as well. Glinka says what DA said about Sb, I see. Double sharp (talk) 11:26, 28 July 2020 (UTC) Citations References Back in 2018 I proposed a simple criterion: Neighbours “ Look at chemical bonds formed by element E with itself and its two closest neighbours in the sense of atomic number. If metallic phases prevail, E is a metal. If covalent or ionic phases prevail, E is a reactive non-metal. If bond absence prevails, E is a noble gas. ” Droog Andrey (talk) 11:48, 3 August 2020 (UTC)

Categorising nonmetals

​​​​​I've been looking again at categorising the nonmetals.

We may discern: (a) H, C, N, O, P, S and Se; (b) the halogen nonmetals; and (c) the noble gases.

I'll set aside the noble gases.

The halogen nonmetals F, Cl, Br, and iodine are called that in recognition of their tendency to form "salts". The name "halogen" means "salt-producing". The etymology is Greek halo, ἅλς, ἁλο- salt; French -gène, ultimately representing Greek -γενής, γεν- root of γίγνεσθαι to be born, become, γεννάειν to beget, γένος kind, etc. Thus, from our halogen article: "When halogens react with metals, they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide." The IUPAC Gold Book defines a salt as, "a chemical compound consisting of an assembly of cations and anions". Bear in mind that while the halogens tend to give rise to salts, they can also (less often) produce non-salts.

Now, when it comes to the type (a) nonmetals, they tend to form polymeric or covalent compounds, bearing in mind that (to a lesser extent) they can also produce salt-like compounds (the azides, for example). A little clarification about oxygen. Metal oxides are usually ionic. On the other hand, oxides as a whole, including the metalloids and nonmetals, are usually either polymeric or covalent. A polymeric oxide has a linked structure composed of multiple repeating units.

So, is there a word meaning either "non-salt" or "non-ionic compound", where non-ionic means polymeric or covalent?

"Coactive" means, "acting in concert; acting or taking place together". That seems like a good word wrt the covalent compounds of H, C, N, O, P, S and Se. For their polymeric compounds, e.g. of H, N, O or S, the connection is to the linked nature of their repeating structural units. Thus, there would be (1) "coactive nonmetals"; (2) halogen nonmetals; and (3) noble gases. That is how the literature tends to deal with the nonmetals, except that it has no common term for the first category.

Bear in mind the expression coactive nonmetals is not currently found in the literature. For me, that is not such a big issue given the schemozzle-like state of nonmetal categories in the literature, a topic which I revisit at the end of this contribution. If needs be, I could get it into the literature by way of a journal article. I already have an article in the literature doi:10.1007/s10698-020-09356-6 categorising the nonmetals into metalloids; intermediate nonmetals; corrosive nonmetals, and noble gases. I have no issue with writing another article proposing a slight adjustment to this categorisation scheme. Certainly, a division into coactive nonmetals, halogen nonmetals, and noble gases is easy to remember, giving the popularity of the halogens category.

Further properties that characterise all or most of the type (a) nonmetals, are: (2) their prominent biological roles; (3) their proclivity to catenate i.e. form chains or rings; and (4) their uses in, or as, combustion and explosives.

It’s memorable to see their dualistic Jekyll (#2) and Hyde (#4) behaviours. Sandbh (talk) 05:33, 31 July 2020 (UTC)

It's puzzling that, in the literature, the metals start out loud and proud, as alkali metals; alkaline earth metals; Ln/An; transition metals; and then fade away with the sixteen different names for the post transition metals. Then there are the reasonably well established metalloids, even though their boundary can move around a bit. And then we come to the first of the really well recognised nonmetals, and a train wreck of classification science. They may as well be called the schemozzle nonmetals. After them follow the well-known halogen nonmetals; and the noble gases. Wither the schemozzle nonmetals? On April 1 2021, barring any other developments, shall we categorize H, C-O, P-S, and Se as "schemozzle nonmetals," for a day, in order to draw attention to their plight? Sandbh (talk) 07:40, 30 July 2020 (UTC)

Chain of relationships

The vertical, horizontal and diagonal linkages between the coactive nonmetals.

H → C Chemical similarities between hydrogen and carbon, including the possible relocation of hydrogen to group 14, have been discussed (Cronyn 2003). They include comparable ionization energies, electron affinities and electronegativity values; half-filled valence shells; and correlations between the chemistry of H–H and C–H bonds.

H → C → N → P → S → O Parathion C₁₀H₁₄NO₅PS is an illustrative example of an organophosphorus compound.

H → N Both are relatively unreactive colourless diatomic gases, with comparably high ionization energies (1312.0 and 1402.3 kJ/mol), each having half-valence subshells, 1s and 2p respectively. Like the reactive azide N³⁻ anion, inter-electron repulsions in the H⁻ hydride anion (with its single nuclear charge) make ionic hydrides highly reactive. Unusually for nonmetals, the two elements are known in cationic forms. In water the H⁺ "cation" exists as an H₁₃O₆⁺ ion, with a delocalised proton in a central OHO group (Stoyanov et al. 2010). Nitrogen forms an N₅⁺ pentazenium cation; bulk quantities of the salt N₅⁺SbF₆⁻ can be prepared. Coincidentally, the NH₄⁺ ammonium cation behaves in many respects as an alkali metal anion (Rayner-Canham and Overton 2010 p. 265).

H → N → O Several hydroxo-nitrogen acids or there salts are known of composition H_xN_yO_z (x = 1–3; y = 1–2; z = 1–4). The best example is nitric acid HNO₃.

H → N → O → S Nitrosylsulfuric acid NOHSO₄ is a colourless solid that is used industrially in the production of caprolactam, a colourless solid with a lobal demand of about five million tons per year, the vast majority of which is used to make nylon filament, fiber, and plastics.

C → N With nitrogen, carbon forms an extensive series of nitride compounds including those with high N:C ratios, and with structures that are simple (CN₁₂); chain-like (C₆N₂ for example); graphitic (linked C₆N₇ units); fullerenic (C₄₈N₁₂) or polymeric (C₃N₃ units). Most of the compounds prepared to date also contain quantities of hydrogen (Miller et al. 2017).

C → P Carbon and phosphorus represent another example of a less-well known diagonal relationship, especially in organic chemistry. Spectacular evidence of this relationship was provided in 1987 with the synthesis of a ferrocene-like molecule in which six of the carbon atoms were replaced by phosphorus atoms (Bartsch et al. 1987). Further illustrating the theme is the extraordinary similarity between low-coordinate trivalent phosphorus compounds (in which phosphorous has less than three nearest neighbours) and unsaturated carbon compounds (in which carbon has at least one double bond, or a triple bond), and related research into organophosphorus chemistry (Rayner-Canham 2011; Dillon et al. 1998).

N → P Like nitrogen, the chemistry of phosphorus is that of the covalent bond; the two nonmetals rarely form anions. Despite them being in the same group, and the composition of some of their compounds resembling one another, the individual chemistries of nitrogen and phosphorus are very different (Wiberg et al. 2001, p. 686). That said, the two elements form an extensive series of phosphorus–nitrogen compounds having chain, ring and cage structures; the P–N repeat unit in these structures bears a strong resemblance to the S–N repeat unit found in the wide range of sulfur–nitrogen compounds, discussed next (Roy et al. 1994).

N → O Nitrogen and oxygen represent the main parts of air. They both become toxic under pressure thus, nitrogen narcosis; oxygen narcosis. They react readily with one another. Nitrogen forms several oxides, including nitrous oxide, N₂O, in which nitrogen is in the +1 oxidation state; nitric oxide, NO, in which it is in the +2 state; and nitrogen dioxide, NO₂, in which it is in the +4 state.

Many of the nitrogen oxides are extremely volatile; they are prime sources of pollution in the atmosphere. Nitrous oxide, also known as laughing gas, is sometimes used as an anaesthetic; when inhaled it produces mild hysteria. Nitric oxide reacts rapidly with oxygen to form brown nitrogen dioxide, an intermediate in the manufacture of nitric acid and a powerful oxidizing agent utilized in chemical processes and rocket fuels.

More generally nitrogen resembles oxygen with its high electronegativity and concomitant capability for hydrogen bonding and the ability to form coordination complexes by donating its lone pairs of electrons. There are some parallels between the chemistry of ammonia NH₃ and water H₂O. For example, the capacity of both compounds to be pronated to give NH₄⁺ and H₃O⁺ or deprotonated to give NH₂⁻ and OH⁻, with all of these able to be isolated in solid compounds.

N → S Nitrogen and sulfur have a diagonal relationship, manifested in like charge densities and electronegativities especially when sulfur is bonded to an electron-withdrawing group. The two elements are able to form an extensive series of seemingly interchangeable sulfur nitrides, the most famous of which, polymeric sulfur nitride, is metallic, and a superconductor below 0.26 K. The cyclic S₃N₂²⁺ cation, in particular, serves as an exemplar of the similarity of electronic energies between the two nonmetals (Rayner-Canham 2011, p. 126).

N → O → S Sulfur nitride oxide chain and ring compounds are known of composition S_xN_yO_z (x = 3,4,7,15; y = 2,4,5,6; z = 1,2,5,8).

O → S Oxygen and sulfur react readily with one another, forming lower sulfur oxides (S_nO, S₇O₂ and S₆O₂); sulfur monoxide (SO) and its dimer, disulfur dioxide (S₂O₂); sulfur dioxide (SO₂); sulfur trioxide (SO₃); higher sulfur oxides (SO₃ and SO₄ and polymeric condensates of them); and disulfur monoxide (S₂O). The burning of coal and/or petroleum by industry and power plants generates sulfur dioxide (SO₂) that reacts with atmospheric water and oxygen to produce sulfuric acid (H₂SO₄) and sulfurous acid (H₂SO₃). These acids are components of acid rain, lowering the pH of soil and freshwater bodies, sometimes resulting in substantial damage to the environment and chemical weathering of statues and structures. In most oxygen-containing organic molecules, the oxygen atoms can be replaced by sulfur atoms.

P → S (Se) Phosphorus reacts with sulfur and selenium (and oxygen) to form a large number of compounds. These compounds are characterized by structural analogies derived from the white phosphorus P₄ tetrahedron (Monteil and Vincent 1976).

S → Se Commonalties between sulfur and selenium are abundantly obvious. For example, selenium is found in metal sulfide ores, where it partially replaces sulfur; both elements are photoconductors—their electrical conductivities increase by up to six orders of magnitude when exposed to light (Moss 1952).

*     *     *

Somewhat like the post-transition metals, the coactive nonmetals have represented terra incognita in terms of a holistic treatment. We record a dozen different organisational arrangements and class names for them, including other nonmetals. To my knowledge this is the second time the relationships among the nonmetals in this part of the periodic table have been delineated in other than a group-by-group or perfunctory manner. --- Sandbh (talk) 08:43, 30 July 2020 (UTC)

Clockwise 45° rotation

To properly gauge the diagonal relationships among the non-metals, the arrangement of the early non-metals can be rotated clockwise by 45 degrees to bring their diagonal relationships into the vertical.

O, being the shape it is, minds it own business. ^_^

The new arrangement suggests four extra diagonal relationships among the non-metals. These are found in the literature but not recognised as such:

B → P

1. B₂O₃ and P₄O₆ are each white polymeric glass-forming acidic oxides
2. Boron‐phosphorus compounds and multiple bonding

Si → Se

1. SiO₂ and SeO₂ are each white polymeric glass-forming acidic oxides
2. New developments in the chemistry of silicon selenides
3. Si and Se: Two vital trace elements that confer abiotic stress tolerance to plants
4. Si_xSe_1−x glasses with x ⩽ 0.17 exhibit remarkable systematics

C → S

1. CO₂ and SO₂ are each colourless glass-forming acidic oxides (CO₂ at 40 GPa)
2. Organosulfur compounds
3. CS₂, which polymerizes upon photolysis or under high pressure to give an insoluble material called car-sul or "Bridgman's black", named after its discoverer; trithiocarbonate (-S-C(S)-S-) linkages comprise, in part, the backbone of the polymer, which is a semiconductor
4. C₃S₂ is a deep red liquid that readily polymerizes at room temperature to form a hard black solid

H → O

1. The two together form aqua vitae. Amorphous ice, as used in cryogenic electron microscopy, is a glass.
2. Water is a spectacular anomaly. Extrapolating from the heavier hydrogen chalcogenides, water should be "a foul-smelling, poisonous, inflammable gas…condensing to a nasty liquid [at] around –100° C". Instead, due to hydrogen bonding, water is "stable, potable, odourless, benign, and…indispensable to life" (Sacks 2001, pp. 204–205). Other H-O compounds are the peroxide, trioxide, tetroxide, and pentoxide. Alkali metal ozonide salts of the unknown hydrogen ozonide (HO₃) are also known; these have the formula MO₃.
3. There are the ubiquitous ionic forms namely the hydroxyl anion OH^– and the hydroxonium H₁₃O₆⁺ cation.
4. Finally, there is the protonated superoxide HO₂ or hydroperoxyl. This plays an important role in the atmosphere and, as a reactive oxygen species, in cell biology. See: HO₂•: The forgotten radical.

• Sacks O 2001, Uncle Tungsten: Memories of a chemical boyhood, Alfred A Knopf, New York

In the regular PT these four relationships appear as putative knight's move relationships. --- Sandbh (talk) 05:16, 3 August 2020 (UTC)

Categories more broadly

I can now breathe a huge sigh of relief, as it would have really spoiled my day to have two of my best WP friends have a falling out with each other. I do have a few thoughts

1. I am a bit queasy about the idea of getting a journal article published in order to have something in a RS that we can quote. In writing this now it occurs to me that I should have AGF and presumed that this was not the only or even the primary motivation, and also assumed that there would be no attempt to self cite unless it was picked up by others. (God help us if disputogen ever appears in a RS.)
2. Submitting a dispute about the appropriateness of citations from technical articles seemed to me to be a fool's errand. The WP denizens who would be likely to respond to this would be very unlikely to have the stamina to read through all of the detailed technical material to say nothing of the technical expertise to make sense of it all. I did have some ideas about how we could have created an appropriate resolution process, but thankfully it was not needed.
3. The concern about our categorization scheme being WP:OR does raise a bit of a niggle with me. But I agree that it does serve a useful purpose pedagogically and in arousing interest and engagement, so I am loathe to throw the baby out with the bathwater. One of the dangers of the YBG rules is that if we use a scheme satisfying those rules it might tend to imply greater certainty than actually exists. It might be helpful to seek out presentation schemes that imply less certainty. We have considered and rejected using stripes or other multi colored techniques, but maybe there is some other way.
4. RL and WP stress are real problems, and if they occur together, they compound the stress. Wikibreaks or semibreaks can be very helpful, especially if used as a prophylactic before the onset of symptoms rather than as a curative afterwards. For several years now I have taken an annual wikibreak, and this has proven to be very helpful
5. I had some more points that I cannot remember now. Sigh.

All the best! YBG (talk) 07:14, 8 August 2020 (UTC)

@YBG: It's good and refreshing to hear from you.

OR. Our categorisation scheme is not OR, is it? AM, AEM, Ln, An, TM, PTM, Metalloids, NG are found in the literature. The remaining nonmetals were called by our WP:ELEMENTS predecessors as other nonmetals. We now call them reactive nonmetals which, well… they are(!), compared to the NG. This term is found in the literature: "The reactive nonmetals include the halogens and other nonmetals" (Burns & Hill 1995, Essentials of chemistry, p. 186). Our PT is a summary visual depiction of what is written in the literature.

YBG rules. Thank you for reminding us of the YBG rules. That is another great outcome of our work here. I suggest there is no meaningful danger of a YBG scheme implying greater certainty than actually exists, in the same way that this is not an in issue for the concept of a chemical group. We discuss this in our periodic table article, thus, "Placing elements into categories and subcategories based just on shared properties is imperfect. There is a large disparity of properties within each category with notable overlaps at the boundaries, as is the case with most classification schemes."

Non-metal categories. More deeply, there were the series of mega-discussions about the loathed "other nonmetals" category, which led to where we are now, with (a) reactive nonmetals and (b) NG, as the most suitable high-level unobjectionable solution. My recollection is we were stymied by the seemingly uncategorisable nature of the other metals.

Coactive nonmetals. I suggest a scheme of coactive, halogen, and NG nonmetals, meets the YBG rules. A bonus is that these three categories already appear in the literature as other nonmetals, halogen, and noble gas nonmetals. My reservation is that "coactive nonmetals" does not appear in the literature as a name for the other nonmetals. That said, "coactive" is a real word.

I intend to publish this scheme as an update to my first scheme in FoC. It'll be a good to bring more characterizational certainty to the other nonmetals, which the coactive nonmetals label does, in five different ways.

The "other" ^_^ thing is that this will be an outcome of our endeavours here. I might write it up in a journal but I'm only standing on the shoulders of WP:ELEMENTS, and other editors. We finally cracked the other nonmetals mega-conker.

The nonmetal categorisation landscape, aside from the metalloids, halogens, and NG, is schemozzle anyway, and that surely gives us the flexibility to choose which name we use for {H, C, N, O, P, S and Se} in the interests of building a better encyclopaedia. The rubbish name "other nonmetals" partly explains why Zuckerman and Nacho (1977) said "The marvelous variety and infinite subtlety of the non-metallic elements, their compounds, structures and reactions, is not sufficiently acknowledged in the current teaching of chemistry."

The importance of classification. From: Minelli, A.: The nature of classification: Relationships and kinds in the natural sciences—By John S. Wilkins and Malte C. Ebach. Systematic Biology. 63 (5), pp. 844–846:

"At any given time, during the historical development of a scientific discipline, classification of available evidence offers itself as the explanandum that asks for a theory (or alternative theories) able to explain it. But this is just one segment in a potentially unending chain of recursive relationships between classification and theory. Theory and classification indeed change over time. As a consequence, the theory that provides explanation for the data organized in a classification at a given time can influence subsequent classificatory effort, and so on. “By means of this a discipline advances: each new pattern raises questions that call for explanations, and each verified phenomenon or fact gives a new pattern” (p. 163). What counts as a fact or a theory is a matter of temporal relativity. The authors’ “concern is that we do not replace observation with theory and think that we have made some progress. Science is founded upon empirical observations, no matter how these are tied up with local and cross-disciplinary theoretical commitments or stances. Once we abandon this aspect of science…science becomes little more than a matter of worldviews and epistemic statements of faith” (p. 163)."

That's why, as I see it, it's important to strive to get the nonmetals right. Sandbh (talk) 04:48, 9 August 2020 (UTC)

@YBG, Дрейгорич, and R8R: Regarding colour schemes, here's a suggestion. Not for the choice of colours, but to instead show that only seven colours are required. Note especially, that the transition metals and noble metals have the same colour (just as they do now), but that the noble metals are intentionally flagged or "crowned" to show their noble status. I've shown other nonmetals, rather than coactive nonmetals as R8R, so far, does not think coactive nonmetals will do. Sandbh (talk) 01:51, 12 August 2020 (UTC)

Is it necessary to separate the halogens from the other nonmetals if we're not separating the alkali and alkaline earths from each other? I would propose six categories: active metals (groups 1+2), transition metals (d+f blocks), post-transition metals, metalloids, reactive nonmetals (non-noble gases... pre-noble gases?), and noble gases. ― Дрейгорич / Dreigorich Talk 03:32, 12 August 2020 (UTC)

​@Дрейгорич: The alkali metals and the alkaline earth metals are reasonably comparable. In contrast, the traditional aspect of teaching the periodic table is to contrast the alkali metals with the halogens (although I see YBG has some thoughts about this which I haven't yet looked closely at). So that'd be a relatively strong consideration. I've never seen it but I'd expect dropping some sodium into bromine would be illustrative, if not explosive. Another observation is the distinction between the halogen nonmetals and the other nonmetals is relatively easily made. So:

"The electropositive elements are on the left side of the chart and the electronegative elements on the right. In any given horizontal row of representative elements, the alkali metal element is the most electropositive element, and the halogen the most electronegative. Elements midway between these two extremes are relatively weakly electropositive and relatively weakly electronegative." --- Gregg DC 1961, College chemistry, Allyn and Bacon, Boston, p. 125 "Across each period is a more or less steady transition from an active metal through less active metals and weakly active non-metals to highly active nonmetals and finally to an inert gas." (Beiser 1968, p. 234) "Between Groups I and VII there are gradations from active metals (Col. I) to less active metals to moderately active nonmetals to volatile nonmetals (halogens Col. VII)." --- Perlman JS 1970, The atom and the universe, Wadsworth Publishing, Belmont, California, p. 439 "A period represents a stepwise change from elements strongly metallic to weakly metallic to weakly nonmetallic to strongly nonmetallic, and then, at the end, to an abrupt cessation of almost all chemical properties." --- Booth VH & Bloom ML 1972, Physical science: a study of matter and energy, Macmillan, New York, p. 426 "Since the elements along this line are neither strongly metallic nor strongly nonmetallic, they are called metalloids." --- Fuller EC 1974, Chemistry and man's environment, Houghton Mifflin, Boston, p. 207 "…the strongest nonmetals, as we have seen, are the halogens." --- Young HD 1976, Fundamentals of waves, optics, and modern physics, McGraw-Hill, New York, p. 332 "With the exception of the Li–Cs group there are closer similarities within the [halogen] group than in any other in the Periodic Table." (Cotton & Wilkison 1999, p. 547)

Table 1: NONMETAL PROPERTIES

Nonmetal	Ionisation energy (kJ/mol)	Electron affinity (eV)	Electro-negativity
H	1,318	73	2.2
C	1,093	122	2.55
N	1,407	−0.07	3.04
P	1,018	72	2.19
S	1,006	200	2.58
Se	947	195	2.55
O	1,320	141	3.44
F	1,687	328	3.98
Cl	1,257	349	3.16
Br	1,146	324	2.96
I	1,015	295	2.66
He	2,372	−50	5.5
Ne	2,088	−120	4.84
Ar	1,521	−96	3.2
Kr	1,351	−60	2.94
Xe	1,170	−80	2.4
Rn	1,037	−70	2.06

Have a look at Table 1, and see how the halogens have consistently high IE, EA and EN.

Similarly there here is a pretty good distinction between the transition metals and the Ln/An. Sandbh (talk) 05:35, 12 August 2020 (UTC)

Only EA seems to be a good distinguisher between the halogens and the other reactive nonmetals, as the other criteria mix the reactive nonmetals with the halogens - there are reactive nonmetals that score higher than halogens. Only EA makes a clear division between them. ― Дрейгорич / Dreigorich Talk 12:18, 12 August 2020 (UTC)

@Дрейгорич: What distinguishes the halogens is that they’re the only nonmetals each having high values for IE and EA and EN. The noble gases are distinguished by, among other things, not having any EA. Before the noble gases were discovered, nitrogen was called a noble gas. Sandbh (talk) 13:39, 12 August 2020 (UTC)

Interesting. Didn't know that, thanks. ― Дрейгорич / Dreigorich Talk 16:05, 12 August 2020 (UTC)

Unification of AM and AEM

I think that a unification of AM and AEM into one category is rather uncalled for, for Wikipedia at least. Both names are better known than any combination of the two.

I would assume that a unified s-block category also calls for more unification: one category for the f-block, for instance, and fewer categories for the p-block. Yet we still have two categories for the d-block and five for the p-block (but also zero for the f-block). I don't see a good consistency here.--R8R (talk) 11:44, 1 September 2020 (UTC)

@R8R and YBG: The AM and AEM names are better known, I agree. That said, our table is not a group-by-group table. Rather, it is more of a metallicity-nonmetallicity table, consistent with the seven quotes from the literature in the above quote box. That is why we do not have categories for the individual p-block groups, apart from the noble gases. From that perspective, the categories of AM and AEM are somewhat inconsistent. A unified s-block category does not necessarily call for more unification; chemistry is full of idiosyncrasies.

In any event, as well as our metallicity categories, we also show the group names in the bigger table, and we used to show the Ln and An labels too. Sandbh (talk) 08:11, 5 September 2020 (UTC)

I'm not sure our table is a metallicity-nonmetallicity table, I wouldn't put it with that. Only our p-block really has this theme. The d-block, for instance, is collectively called the "transition metals" even though they differ a lot by chemical properties (compare, say, copper and zinc on one hand and gold on the other). The existence of a lathanide category is not covered by the description of our table as a metalicity-nonmetalicity table, and the actinides are rather diverse, too, perhaps too diverse for a single grouping if we consider that it's best to split off the four main halogens from the rest of the reactive nonmetals. However, we use those names (TM, Ln, An) because they are widely known (unlike the name "reactive nonmetals" which we can sacrifice because it's not that well-known), and that's the best criterion for Wikipedia I can think of, and that's why we use them. The same goes for AM and AEM. We should stick to these categories here to remain oriented towards the general reader and the description they may find elsewhere. This doesn't invalidate the idea as a whole, I'm merely saying that this is not the place.--R8R (talk) 10:20, 5 September 2020 (UTC)

@R8R and YBG: As per the literature, the transition metals represent a transition from the physically weak but chemically strong metals to their left, and the physically and chemically weak metals to their right. A quick look at the electronegativity values for the s-block metals and the f-block shows a similar gradation in diminishing metallic character.

The complete L-R gradation is s > f (i.e. Ln/An) > d (transition) > p metals > metalloids > pre-halogen nonmetals > halogen nonmetals ~> noble gases. This phenomenon is discussed in our periodic table article.

AE and AEM are not worth keeping as category names as we include them along the top of our main periodic table as group names, together with all the other group names including the halogens. That is the beauty of it: being able to appreciate the table by category and by group. Having the AE and AEM as categories and as groups is an unnecessary duplication. Sandbh (talk) 13:16, 6 September 2020 (UTC)

I agree with @R8R: in his doubts that our table is a metallicity-nonmetallicity table. Our color scheme is certainly oriented in that direction, and I suppose that one could say that the color scheme is one of the distinguishing features of the enwiki PT. I take issue with @Sandbh:'s previous statement our periodic table is not a groupic table. It is a metallicity table. I think his recent statement That is the beauty of [the enwiki PT]: being able to appreciate the table by category and by group.

I agree with @Sandbh: that having the AE and AEM as categories as well as groups is an unnecessary duplication. On this same basis I say that having the Halogens as both a group and as a category is an unnecessary duplication. Of course, the same logic applies to the noble gasses - but as I've said before, if any group is distinct enough to merit being both a group and a category, it is the noble gasses.

—YBG (talk) 23:08, 6 September 2020 (UTC)

@R8R and YBG: I suspect our table is not the first to use colour categories and that, these days, names like alkali metals, and alkaline earth metals sound rather old fashioned, although still part of the lexicon. Halogens and noble gases are fine. We wouldn't really have a category and a group each called "halogens". There would be the group 17 halogens (F, Cl, Br, I, At, Ts); and the halogen nonmetal category (F, Br, Cl, I):

Periodic table blocks, group names, and metallicity colour categories

−− s −−	−− f −−	−−−− d −−−−		−−−−−−−−−−−−−− p −−−−−−−−−−−−−−
1. Alkali metals 2. Alkaline earth metals	3 (La-Ac)	3 (Sc-Y); 4−11	12	13−16	14. 15. Pnictogens 16. Chalcogens	17. Halogens	18. Noble gases
Metal				Metalloid	Nonmetal
Pre-transtition metal	Lanthanoid	Transition metal (✣ = noble metal)	Post transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
	Actinoid

--- Sandbh (talk) 03:57, 7 September 2020 (UTC)

Here are several examples from the literature, including the use of the pre-transition metal label:

1. "The pre-transition metals. These occur in Group IA and IIA of the Periodic Table, and for a number of purposes it also convenient to include with these the Group III metals, Al, Sc and Y…" Phillips and Williams (1966, p. 4)
2. "In contrast , the coordination chemistry of the ocean would , at first, seem to be the exclusive province of the pretransition metals; this is seen clearly by looking at an average composition of an ocean" (ACS 1967, p. 256)
3. "The ionic hydrides chiefly comprise the pre-transition metals: alkalis, alkaline earths, etc." (Goldschmidt 1967, p. 446)
4. "The chemistry of these elements [AEM] resembles that of the IA metals to a large degree. (Hamm 1969, p. 369)"
5. "It is convenient to deal with the subject by considering the derivatives in turn of the three main types of metal: (a) light and pre-transition metals (Li, Mg, Al etc.); (b) the post-transition metals (Zn, Sn, Pb etc.); (c) the transition metals (Ni, Pd etc…" (Nyholm 1970, p. 35)
6. "The difference between the Group I and Group II elements (except Be) is more of degree than kind." (Choppin and Russell 1972, p. 334)
7. "This concept will be considered in Chapter 2, but suffice it to say here that complexes of the pre-transition metals (Na+, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Al³⁺) are held together by electrostatic forces…" (Eichorn 1973, p. 4)
8. "In this scheme, the alkaline-earth metals, Ca, Sr, and Ba, may be regarded as pre-transition metals and the noble metals, Cu, Ag, and Au, as post-transition metals." (Collings 1984, p. 46)
9. "Aluminium and the elements of groups 1 and 2 are classed as pre-transition metals…" (Cox 2012, p. 188). Cox also discusses the properties of the pre-transition metals as a whole, as did Deming (1940, pp. 650‒672), the guy who popularized the medium-long form of the periodic table (except he called them light metals).
10. "Pre-transition-metal oxides (e.g. MgO, Al₂O₃, etc.) usually are good insulators and inert to redox gas molecules" (Wang & Gouma 2012, p. 169).

--- Sandbh (talk) 07:45, 7 September 2020 (UTC)

@Sandbh and YBG: I don't see how "alkali metals" or "alkaline earth metals" are old-fashioned. Is it a personal feeling? If not, are "halogens" and "noble gases" also not outdated? If not, why those two aren't outdated while the other two are?

I don't see why having a column and a category overlap completely is that much of a problem. I really don't. And if that confusion weren't enough, we also have the "noble gases" category that's not going away, which is precisely a group-category. Why is it okay in that case but not in the other?

I'm not saying that the idea is unworkable, not even in principle. I'm noting that, however, we in Wikipedia are a tertiary source, and we must first of all reflect on what others say. While I don't doubt that the 'pre-transition metal" label exists, AM and AEM are both well-established categories, both more widely known than the merger, as you noted yourself a few messages ago. That is the ultimate argument as I see it. That was also how we ended up with a -La-Ac group 3: not because it's better but first and foremost because it's more common, and that's a fine line of argumentation as I see it, and that's the number one line of argumentation as long as Wikipedia is concerned. This change is uncalled for here at the time; this assessment may change if chemical literature embraces the "pre-transition metal" label more closely. It may be a worthy change but it shouldn't start here.--reaR8R (talk) 17:28, 9 September 2020 (UTC)

@R8R: For the record, I think that the old fashioned argument should be completely disregarded.

To me, the crux of the matter is why we have categories at all. I suggest that the reason why we have categories is to provide some broad, high-level organization that enables the reader to see the structure of the PT. A few general principles flow out of our primary goal, serving the reader.

1. The number of categories should be small, ideally 7±2.
2. The categories should present information that is not otherwise obvious in the PT.

Our current 10 categories (counting unknown properties) seem to me to be unwieldy, particularly in how they make exacerbate the difficulties of selecting a good set of colors that satisfy the need for contrast and accessibility issues. (This is the reason why I apply the 7±2 ideal to the entire set of categories and not separately to the metal and nonmetal categories, which would be sufficient for "chunking".) Consequently, I am inclined to oppose Sandbh's proposal to subdivide the reactive nonmetals into pre-halogens and halogens, and I am generally inclined to support Sandbh's proposal to merge AM and AEM.

I say "inclined" because this reason in and of itself is not sufficient for a final decision.

Let me start by making the case for the noble gasses being a one-group category. The NG are so different from all of the other elements that a perfectly reasonable 2-category PT would have the NG in one category and everything else in another category. All of the other elements share a common characteristic (reactiveness) that none of the noble gasses have. Yes, it is true that the NG form compounds, but only under coercion. And it is true that the gold group is also noble. But the gap between the least most-reactive noble gas and the least-reactive of the other elements is a wide gulf indeed. Thus it makes good sense for the NG group to be elevated to category status.

Now consider applying the same standard to groups 1 and 2.

Yes it is true that the AM elements share common characteristics that none of the other elements share. Likewise, the AEM share common characteristics that non of the other elements share. But the pertinent questions are much stronger. Do all of the non-AM-elements share a common characteristic that the AM lack? Does that characteristic divide the AM and non-AM with a wide gap? Do all of the non-AEM-elements share a common characteristic that the AEM lack? Does that characteristic divide the AEM and non-AEM with a wide gap? If these are the true, then I would heartily agree that the AM group and the AEM group should reasonably have elevated category status.

But this is not the case, and in fact the AM and AEM, while different, share many common characteristics.

By representing groups/families as labeled columns, our PT already identifies the AM and AEM. If there were only 4 or 5 other categories, I would be in favor of keeping the AM and AEM separate. But because we have 7 or 8 other categories, I believe our categorization scheme will be improved by merging them into an "active metal" or "pre-transition metal" category. The terms "alkali metal" and "alkaline earth metal" will continue to exist as group/family names, just not as separately named and separately colored categories.

YBG (talk) 18:52, 9 September 2020 (UTC)

I appreciate the YBG reasoning here, as in: keep it as a category if it can stand up to all other elements. It's a strong test. However, when arguing that 10 categories is unwieldy, particularly in how they make exacerbate the difficulties of selecting a good set of colors that satisfy the need for contrast and accessibility issues. I've made some off-wiki research and excercises and one can be sure, even 'only' seven categories do not eliminate accessability-issues (like colorblindness, contrast). Also, those issues could be alleviated by other methods. All in all, I appreciate the tough requirements, checks and tests YBG introduces; and I'd prefer this discussion not be coerced because of sole coloring issues. IOW: if the PT would need 14 categories, coloring is the smallest problem. -DePiep (talk) 19:15, 9 September 2020 (UTC)

@R8R, YBG, and DePiep: I suggest the halogen group or category name is the most popular name in the literature alongside the noble gases. Yet—to my complete astonishment—we got rid of it like falling off a log, without any tears; fuss; hue and cry; or objections. Why? Because it's still there as a group name, as it should be. I agree with DePiep that colouring is the smallest problem. I support the pragmatic application of the 7±2 rule, as an ideal, yet not ahead of the principles of good classification science. It is quite an achievement to get the 118 elements down to nine categories. The pre-transition metal + pre-halogen nonmetal scheme falls within the 7±2 rule, at nine categories; I don't count "unknown properties" as a category. "Unknown" just means "in the waiting room, pending assignment to a category".

@R8R: May I ask for a little movement on your part in the same good spirit as your support for getting rid of the halogen category, yet (most importantly) keeping the AM and AEM as displayed group names, noting your support for bifurcating the reactive nonmetals?

@YGB: May I ask for a little movement on your part in supporting a reactive nonmetal split, noting the WP PT has featured such a split for the last 16 of 18 years (with ten[!] categories, not counting the unknown properties pseudo-category), and that I support your proposal for a group 1-2 merge?

@DePiep: thank you for chiming-in with your thoughts.

For my part I will support the retention of metalloids as a major category, noting they are no more than chemically-weak nonmetals, a fact that has been known, and recorded in the literature for over 120 years.

I feel neither of my requests represent die-in-a-ditch matters. Sandbh (talk) 06:44, 10 September 2020 (UTC)

re the halogen group or category name by Sandbh. For sure, halogen is undisputed a group name. That should do, it is in our PT. A more relevant question would be whether we are fine with the words "metal, nonmetal" being only present in secondary order (to be deducted from the legend). Now, I do not see why squeezing 'halogen' into a category name too would help or clarify anything. (Even the construction cat:halogen nonmetals / grp:halogens is not helpful except for using the word once more; consider "f-block lanthanides"). Then re lamenting "—to my complete astonishment—we got rid of it": well, who wrote "...astatine is currently better classified as a metalloid" then back in 2012, and more? I don't think this meandering and free thought releasing helps towards a sound decision base for category changement. Is there a basic structure of approach here I am missing? -DePiep (talk) 14:36, 10 September 2020 (UTC)

@DePiep, R8R, and YBG: For clarity, here is what I have in mind:

Periodic table blocks, group names, and metallicity colour categories

−− s −−	−− f −−	−−−− d −−−−		−−−−−−−−−−−−−− p −−−−−−−−−−−−−−
1. Alkali metals 2. Alkaline earth metals	3 (La-Ac)	3 (Sc-Y); 4−11	12	13−16	14. 15. Pnictogens 16. Chalcogens	17. Halogens	18. Noble gases
Metal				Metalloid	Nonmetal
Pre-transtition metal	Lanthanoid	Transition metal (✣ = noble metal)	Post transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
	Actinoid

The labels metal and nonmetal are included in group or category names where appropriate.

We took a considered approach to categorising astatine. Immediately following its production in 1940, early investigators considered it a metal. In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal. In 1950 astatine was described as a halogen and (therefore) a nonmetal. In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure.

We first changed it from a nonmetal to a metalloid. In 2013 it was predicted to be metal. We didn't doing anything about that for a while. Since the article was published it has been cited 35 times without dissent. So we changed the category of At to a post-transition metal.

The above colour category proposal means there is still, as there always has been, a halogen Group 17, comprising the nonmetals F, Cl, Br and I, and the metal At.

If no one likes highlighting the noble metals then that is another matter I won't die in a ditch over.

As I see it, the structured approach to categories is:

1. good classification science;*
2. categories are usually defined by more than two attributes;
3. such attributes are found in the literature;
4. categories may change over time as new insights are uncovered
5. the 7±2 rule where feasible;
6. categories should be beneficial to an economy of description, to structuring knowledge, and to our understanding; and
7. hard cases should constitute a small minority.

* i.e. distinctive categories, whilst acknowledging there is a spectrum of attributes within each class; that the distinction between classes is not absolute; and that boundary overlaps will occur as outlying members in each class show or begin to show less-distinct, hybrid-like, or atypical properties

The context is:

1. for the past 16 out of 18 years we have had three nonmetal categories, with good reason;
2. "other nonmetals" is a less than desirable category name; and
3. the difference between the AM and AEM is more of degree than kind.

--- Sandbh (talk) 01:33, 11 September 2020 (UTC)

I've got a few thing to say about this.

Could I please move?

I could in principle. For instance, if we were writing a book, I think we could have a discussion about whether such a move is a good thing; if it's not clear, then to what extent it is and to what extent it is not, and from there we could have decide whether it was worth it. I don't intend to insist on anything I like best if other things are good enough and somebody feels strongly about them.

House rules

That would be if we were writing a book and thus were free with respect to what we wanted to write. However, we are not writing a book. We are writing for an encyclopedia, which has its own house rules. The principal rule I keep referring to is that Wikipedia is a tertiary source and thus we are supposed to first and foremost what other sources say. This is very important: when in Rome, do as the Romans do.

Are alkali metals and alkaline earth really all that similar?

I'd say whether the difference is of degree or kind is secondary to whether the combined category could exist in this encyclopedia given its house rules.

Other nonmetal?

My thinking was and is that "other nonmetal" is not a term worth replicating as it is generic and meaningless. This is a unique situation, or if I'm wrong and we once upon a time also had "other metals," then I'm sure I propagated a move to "post-transition metals" to add some meaning to the category.

What do the sources say?

According to Google Ngram, the term "pre-transition metal" was in 2019 roughly 1,000 times less popular than "alkaline earth metal" and roughly 4,000 times than alkali metal. Interestingly, the idea that "halogen" and "noble gas" are most popular names for a chemical category of elements is contradicted by the graph, which shows that "alkali metal" was consistently more common than the latter.
This graph also shows the comparison between "metalloid" and "chalcogen" and "pnictogen." It can be seen that "metalloid" is more popular than both, however, it is still less popular than "halogen." The category of metalloids, however, owes its appearance to the existence of the general terms "metal" and "nonmetal". The term "metal" is very well-known in chemistry and beyond, and if you were to add it to the graph, it would dwarf all the other lines, including that of the halogens ("metal" was roughly 75 times as popular as "halogen" in 2019).

There are still groups, we could use those two names there

With all due respect, I don't think this is anything that resembles a trade-off. I never thought about groups in our big table. What I have always looked at is the small table in the infobox, and I sometimes think about the table at the bottom of our articles. This was also never the reason why I advocated the removal of the halogens category back in the day, so I don't see why it could matter now.

In conclusion

If there were a category even remotely resembling in popularity AM and AEM, we could consider it. But there isn't one, so there is nothing to change to given the house rules of Wikipedia. The thinking could be different on a different platform but here, it stands.--R8R (talk) 11:43, 11 September 2020 (UTC)

Ngrams, House rules

Name	Frequency
Heavy metals	1,320
Precious metals	590
Transition metals	300
RE, REE, REM	275
Halogens [G]	200
Noble metals	130
• Base metals • Ferrous metals • Noble gases [G] • Rare earths	120
• Alkali metals [G] • Rare earth elements	115
• Lanthanides • Actinides	100
Metalloids	85
Transition elements	50
• Alkaline earth metals [G] • Rare earth metals	40
Refractory metals	29
• Active metals • Platinum group metals • Reactive metals	25
• Lanthanoids • Light metals • Representative elements	13−15
• Actinoids • Chalcogens [G] • Fusible metals • Main group elements	8−10
• Coinage metals • Electropositive metals • f-block elements • Ordinary metals • Other nonmetals • Volatile metals	4−6
• Native metals • s-block elements	~3½
Inner transition elements	2½
• Electronegative metals • Group 18 elements • p-block metals • Pnictogens [G] • Poor metals • Post-transition metals • Reactive nonmetals • s-block metals • White metals	½−1½
• Acid earths • Helium group • Pre-transition metal • Super metal	0.04–0.07
• Diatomic nonmetals • Polyatomic nonmetals	≈ 0

@R8R, YBG, and DePiep: In an ngram search, the singular forms AM, AEM and halogen are less than relevant since the subject matter is categories of the element types, not individual examples of the elements concerned.

A search of the plural forms yields the ratios you can see in the table. Bold = IUPAC-endorsed. [G] = Group name.

From these results, the recipe for colour category names features, or has featured, a combination of [1] literature popularity; [2] pragmatism; and [3] convenience. Thus, we:

• use transition metals in preference to the IUAPC-endorsed transition elements, as the latter is less popular;
• use metalloids since this category name is more popular than some other IUPAC names, including AEMs (which we do use);
• use post-transition metals as the best of a bad choice;
• used polyatomic nonmetals and diatomic nonmetals as a convenient way to reflect the most popular practice in the literature of having there being two categories of "reactive" nonmetals.

Our colour categories appear to be arbitrary in at least three aspects:

1. no mention of rare-earth metals, a popular and IUAPC-endorsed name;
2. no mention of noble metals, a popular and IUPAC-endorsed name; and
3. the absence of two categories for the "reactive" nonmetals, contrary to the literature.

Item 1 is trumped by the popularity of the lanthanide category.

Item 2 should be addressed, in accordance with our house rules, and this can be done easily, as suggested.

Item 3 should be addressed in accordance with our house rules, and this can likewise be done easily via judicious use of the "halogen" noun, as pre-halogen nonmetals (in the absence of anything better c.f. post-transition metals, as mentioned courtesy of R8R) and halogen nonmetals, which is precisely what they are.

Is there a case for merging the AMs and AEMs consistent with our house rules?

1. We have a precedent i.e. the removal of the highly popular halogens category.
2. The literature provides a precedent: we are not breaking new ground.
3. The alkaline earth metals category is no more popular than the rare earth metals category, and we do not show the latter (for a good reason).
4. While AMs and AEMs warrant separate articles, they are not worth separate colour categories given the difference is one of degree rather than kind. Further, the progenitor of the AEMs, beryllium, is not alkaline; the second member of the AEMs, magnesium, is not an "earth": that is why there is a need for an article on the AEMs, to explain what is going on. Historically, only calcium, strontium and barium were regarded as alkaline earths.
5. The frequency of the s-block metals category name (3½) is remotely—per R8R's request—as popular as the average (77½) of the AMs and AEMs.
6. s-block metals is x3 as popular as the post-transition metals and reactive metals, which we do show.
7. s block is as popular as the AEMs; metals is 250x AEMs.
8. Light metals (15), per Deming, is not unreasonable, being even less remote from the AMs and AEMs.
9. We have a limited amount of real estate available on our small colour category periodic table; an internally weak category is one category too many, consistent with the YBG rules i.e. #3, insufficient between-group dissimilarity. Even the name AEMs was derived from the fact that that the hydroxides of calcium, strontium, and barium, like sodium and potassium hydroxides, have alkaline properties. Said another way, the s-block is not worth a split, whereas the other blocks are (1 split for the f-block; 2 for the d-block (3 if you include the noble metals); and 4 "splits" for the p-block, where the metals meet the nonmetals.
10. Aspirationally, in terms of legibility and readability, this is closer to the worthy 7±2 rule. On an associated note, the "too loud" red shade of the AMs is removed.
11. The above items are consistent with building a better encyclopaedia; there is no OR.
12. The above items are not subject to the deliberations of an IUPAC project. Further we do not follow IUAPC recommendations with respect to the transition metals category name, nor does IUPAC recognise post-transition metals; metalloids (it has a historical record of disavowing its use, or preferring semimetals), or reactive nonmetals.

--- Sandbh (talk) 07:20, 13 September 2020 (UTC)

This is going to be a partial reply to the 12 items. Perhaps it may need added to in the future.

My thinking is that we as a tertiary source (I say this phrase a lot because it really is important) should use categories that are well-known and are well-defined in the literature. The list of such names goes more or less like this: metal, metalloid, nonmetal; alkali metal, alkaline earth metal, rare earth metal, lanthanide, actinide, transition metal, platinum group metals, pnictogen, chalcogen, halogen, noble gas. There are some other names that I would advise against on basis of their ambiguity: for instance, I have no doubts about what the composition of the alkali metals group is; what is the composition of the group of noble metals, does it include, say, gold? mercury? On top of that, we have one more constraint, which is that categories should not overlap. This set of constraints gives us two problems: one is that some categories do overlap and we must choose (we even have an unsolvable overlap between transition metals and lanthanides and actinides), which is why we don't use some names, for instance, rare earth metals and platinum group metals. On the other hand, there are elements that didn't fall in any category, such as carbon, and as such we had "other metals" and "other nonmetals." We eventually changed "other metals" to more descriptive names, IIRC "poor metals" and then "post-transition metals". "Other nonmetals" was harder to get rid of.

Removal of "halogens" is not a precedent. It really isn't, I'm not stretching anything to fit my liking. There were a few advantages other than editorial preference: intersection of halogens and metalloids and existence of a meaningless name (other nonmetals). Neither is a concern with the proposed move in s-block, where we would merely remove two well-known names in exchange for a less-known one to match some editorial preference.

"s-block metals" is 40 times less popular than "alkaline earth metals" and 115 times than "alkali metals." I think that's a bit too distant. Notwithstanding that, I would argue that "s-block metals" is not a name at all, it's merely a description. A name adds some image to a group; even the transition metals are about some transition. Compare "alkali metal" (a name) and "group 1 metal" (not a name). Names are more reader-friendly, and as such I propose we use them as we always have.

Can you specify where IUPAC endorses "noble metals"? The Red Book doesn't mention this name: "The following collective names for like elements are IUPAC-approved: alkali metals (Li, Na, K, Rb, Cs, Fr), alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra), pnictogens8 (N, P, As, Sb, Bi), chalcogens (O, S, Se, Te, Po), halogens (F, Cl, Br, I, At), noble gases (He, Ne, Ar, Kr, Xe, Rn), lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (Sc, Y and the lanthanoids) and actinoids (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr)." (Red Book, 2005) The Red Book also mentions "transition elements" and "inner transition elements."

I will leave aside the discussion whether the s-block merits a split because it's up for sources, not us, to introduce a new name since there are already some names, but such a name is yet to be seen. Just as I won't ask whether Be or Mg should really be in the same category as Cs.

The red of alkali metals is easy to fix. I'd say it's a few hours' work to improve the existing colors. As DePiep (rightly) notes, color choice should not be a consideration for category choice.

We don't need a precedent for a change; we need to see that the number of instances is at least comparable. That is not the case. Removing two well-known names for an unknown or worse, dubious name (I'd argue aluminum is a "light metal," for instance) is not helpful in our quest for building a better encyclopedia. I once again note that I am primarily concerned with encyclopedia-building, rather than pure categorization where more freedom is allowed. It could very well be that a common category for the s-block metals could help you write a better book of your own; I'm merely arguing against using that category in our encyclopedia for the time being. If a name ever picks up, we can reconsider.--R8R (talk) 15:03, 19 September 2020 (UTC)

• • I have taken my time to consider what you said and formulate my response based on this close consideration. I'll try to write it down soon enough.--R8R (talk) 10:57, 14 September 2020 (UTC)
  • So will I. -DePiep (talk) 22:17, 15 September 2020 (UTC)

For starters: Sandbh how is popularity an agument at all? -DePiep (talk) 23:07, 15 September 2020 (UTC)

DePiep: As an encyclopedia we aspire to take account of the literature. The Google ngram bookworm has been criticised for an overabundance of scientific literature! That's the kind of criticism I like. Sandbh (talk) 00:31, 16 September 2020 (UTC)

(point-of-return for DePiep) -DePiep (talk) 23:13, 18 September 2020 (UTC)

Sandbh responds to R8R

@R8R, YBG, and DePiep: Responding to R8R.

Tertiary sources. Yes, I agree these are important. So are well-known, well-defined categories.

Yes, I agree these important aspects sometimes clash, or cannot be so well-attained.

For example:

• At the very start, the boundary between metals and nonmetals is blurry.
• Halogen is a well known collective term, and the most popular of the IUPAC-endorsed names. We do not show it since it clashes with the metalloid category.
• The metalloid category is not well defined. Some authors do not recognise such a category. However, we can at least see, based on the COSMIC database (z = 194), which elements are most commonly recognised as metalloids.

Already we have to exercise some editorial pragmatism. This does not matter as long as we provide the context for doing so, and the basis for the decision.

Noble metals. Rayner-Canham (2018) recently considered how to parse the transition metals, on chemistry grounds. He surveyed the TM classification literature. His biggest sub-category was the noble metals, as PGM + gold. Silver, in comparison, is so much more chemically reactive and has such a different chemistry. Mercury is effectively not a transition metal. Once again we need to exercise some editorial pragmatism. IUPAC does not endorse noble metals as category. Nor do they endorse post-transition metals; metalloids; and reactive nonmetals. The great German text by Wiberg comments, "In place of the noble gases, the transition metal grouping has the noble metals." (2001, p. 1133).

Categories should not overlap. It’s a commendable aspiration but very many categories overlap. The overlaps are not so important. More important is that the categories provide an economy of description, a tool for structuring knowledge, and can also lead to deeper understanding.

Overlaps are solvable. We can show them using diagonal lines of demarcation, as some other authors do. The German Wikipedia has a nice table, in its lead, featuring some of these. This table has its own issues but we can do better.

Taxonomy of our scheme. Our category scheme is based primarily on metallicity and secondly on categories (not Groups):

I. Metals-metalloids-nonmetals

II. Categories.

Note the absence of a Roman-numeral-level for Groups. So the coinage metals, volatile metals, chalcogens, and pnictogens are not shown. Of course, the noble gases are shown as a category and that is fine. The noble gases are not a “Group” per se since they will not be able to accomodate oganesson, which is expected to be a solid, reactive (i.e. not noble) semiconductor (band gap 1.5 eV) having a sub-metallic appearance.

Census of periodic tables in chemistry (COPTIC database)
I looked up the taxonomical structure of periodic tables found in 62 more recent chemistry textbooks:

COPTIC results, preliminary

Taxon (% or average)	Notes (ditto, as applicable)
1. Metal-metalloid-nonmetal (35%)	Metalloid aka semiconductor; semimetal
2. Blocks (15%)	When blocks are shown, nearly all sources show all four.
3a. Categories (~50%)	Actinide; Lanthanide (67.5%) Metal (transition); Transition element; Transition metal (30%)
3b. The rest of the categories (~4.5%)	Hydrogen (~1.5%) Active metal; Light metal; Reactive metal (~5%)^ Inner transition element/metal; Metal (inner transition) (8%) Rare earth (Ln); Rare earth (Ln, An) (3%) Other metal; Poor metal; Post-transition metal (~5%) Life element; Other nonmetal (5%)
4. Groups (~10%)	Alkali earth metal; Alkali metal (8%) Alkaline earth metal (9.5%) Chalcogen (~1.5%) Halogen (11%) Noble gas (~19%)
Sundries (~3.5%)	Main group element; Representative element (~5%) Gas-liquid-solid (~3%) Nil (~3%) Main group metal; Metal (main group) (~3%)

^ Groups 1 and 2

Observations and conclusions

1. The frequency with which the Ln and An are flagged is astonishing.
2. The frequency with which Groups are not flagged is remarkable.
3. 67.5% of sources include the words lanthanides and actinides on their table.
4. Given only 10% of sources (on average) flag Groups, the field is wide open after the allocation of the categories: s-block or equivalent (~20%)§; Ln; An; TM; Metalloid; and Noble gas.
5. Post-transition metals appears to be a reasonable choice for the leftover metals between the TM and the metalloids, given the limited range of names for the metals in this part of the periodic table.
6. I'm not sure I ever understood what was "wrong" about poor metals.
7. Looking subsequently at the ngram results, "Halogen" warrants a place in some fashion, as does "Noble metal".
8. The periodic table in the lead of our periodic table article is deficient given there is no immediately accompanying colour category legend (cf the German example).

§ = s-block (15%) + Active metal; Light metal; Reactive metal (~5%) = ~20%

Nonmetal categories

"While I am eager to be proven wrong, I continue to think that there is no good divide at all. I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one. --R8R (talk) 17:36, 10 September 2017 (UTC)

In light of item 7 above, and table 1 below, this does indeed happen.

The numerous properties that distinguish the halogen nonmetals from the remaining "reactive nonmetals" are set out in the literature. Here they are again:

Table 1: Shared properties of H, C-O; P-S; Se

1. Sub-metallic, coloured or colourless appearance, and brittle comportment if solid	6. Multiple vertical, horizontal and diagonal relationships
2. Moderate net non-metallic character	7. Uses in combustion and explosives
3. Covalent or polymeric compounds†	8. Uses in nerve agents
4. Prominent biogeochemical roles	9. Uses in organocatalysis
5. Proclivity to catenate (form chains or rings)‡	10. Dualistic Jekyll (#4) and Hyde (#7, 8) behaviours.

† A small clarification about oxygen. Metal oxides are usually ionic. On the other hand, high valence oxides of metals, and the oxides of metalloids and nonmetals, are usually either polymeric or covalent.

‡ Since H₃⁺ is featured in interstellar chemistry this could be said to be unconvincing. Yet that is not the point. Instead, there is a spectrum of applicable properties in each category. Carbon is the most prolific catenator. Hydrogen happens to the poor cousin, that is all.

While it is essential that a periodic table displays important trends in element chemistry at ambient conditions we need to keep our eyes open for unexpected chemical behaviour in near ambient, or unusual conditions. A combination of ambient, near ambient, and unusual condition experimental data and theoretical insight supports a more nuanced understanding of complex periodic trends and non-periodic phenomena.

In ambient or near ambient conditions there is more to hydrogen:

• Theories of the structure of water involve three-dimensional networks of tetrahedra and chains and rings, linked via hydrogen bonding.
• A polycatenated network, with rings formed from metal-templated hemispheres linked by hydrogen bonds, was reported in 2008.
• In organic chemistry, hydrogen bonding is known to facilitate the formation of chain structures. C₁₀H₁₆O 4-tricyclanol, for example, shows catenated hydrogen bonding between the hydroxyl groups, leading to the formation of helical chains; crystalline isophthalic acid C₈H₆O₄ is built up from molecules connected by hydrogen bonds, forming infinite chain.
• In unusual conditions, a 1-dimensional series of hydrogen molecules confined within a single wall carbon nanotube is expected to become metallic at a relatively low pressure of 163.5 GPa. This is about 40% of the ~400 Gpa thought to be required to metallise ordinary hydrogen, a pressure which is difficult to access experimentally.

In light of these further considerations I argue that hydrogen has a not insignificant linking capacity.

Light metals

"If there were a category even remotely resembling in popularity AM and AEM, we could consider it. " R8R (talk) 11:43, 11 September 2020 (UTC)

Deming included Al among the light metals, along with the group 1 and 2 metals. It’s a good category name since that is exactly what these metals are. The link between Be and Al is strong. And light metals avoids the problems with the "alkaline earth metals" name i.e. that Be and Mg are not alkaline earths. Light metals got an Ngram of 13-15; the AM and AEMs average 77. I’d say 18% is more than good enough to regarded as, at least, "remote".

Light metals is fourteen times as popular as post-transition metals and reactive nonmetals, both of which we show.

Objective

Here's where this is headed; I've discussed replacing the lanthanides with the rare earth metals elsewhere:

Legend 3: Periodic table categories

Metal				Metalloid	Nonmetal
Light metal A	Rare earth metal	Transition metal (ρ, ✣)	Post-transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
	Actinide

A Including aluminium

ρ Transition (rare earth) metal: Sc, Y, La

✣ Transition (noble) metal: Ru-Pd, Os-Pt, Au

Rare earth metal is there in light of its ngram popularity, and the fact that at least the label "Lanthanide series" ought to be shown on our table. That is, the lanthanide category name will be retained. R8R: I see you responded to the rare earth proposal separately; I'll follow on with a response.

YBG supports a merge of AM and AEM, as do I. R8R has expressed support for two nonmetal categories, in addition to the noble gases. I support this one too.

R8R: In terms of encyclopedia-building, all of the above more closely follows the literature than is the case now. It therefore represents an improved taxonomy.

I'll draft a better PT for the lead of our article, for you all to consider.

DePiep: Grateful for your thoughts. Sandbh (talk) 06:42, 21 September 2020 (UTC)

Well-known, well-defined categories. I absolutely agree on that they are important. We are on the same foot about this.

We have to exercise some pragmatism, that's right, too. However, we must not exercise more pragmatism than we absolutely have to. This limitation is specific to Wikipedia and it's a big part of why I keep repeating it's important that we are writing a tertiary source. If halogens were more important than metalloids, then it would only be natural we had chalcogens, too, and perhaps pnictogens. Where carbon goes then remains a mystery. So in terms of a whole picture having metalloids over halogens is very clear. This groups 1-2 issue, however, does not have such far-reaching consequences; it doesn't affect anything else (I'll take it Al is fine either way).

Noble metals To quote you, "once again we need to exercise some editorial pragmatism," and therein lies the problem. This is not some pragmatism that we absolutely have to exercise. It's a good hint that we may not need this category at all. Alone, it does not prove anything, of course, because there are some ties such as whether group 12 elements should be colored as TMs or PTMs, but it's a very good sign. Yet I still don't see the need to include this term in our general classification in the first place. For example, this suggestion moves us further from the 7±2 argument that has just been used in a different circumstance. Whereas I don't think 7±2 argument is the sole arbiter, I agree with the general point that there shouldn't be more categories that there have to be. We already have those elements covered as TMs. There's no real need for more; that's just enough. Just because a term exists doesn't mean we should display it in our general classification, just as we don't display the term "chalcogen," for instance.

Categories should not overlap Once again, a quote: "More important is that the categories provide an economy of description, a tool for structuring knowledge, and can also lead to deeper understanding." The big question is, what description do we want to use. What knowledge should we structure? Could it be we wanted to display and structure too much knowledge for a single graph? I think that's a case of what we're having here. I don't disagree with what you said, I simply mean to say that it wasn't an argument for your side (or mine): you could interpret those words however you like. Having to have no overlaps, however, is a tangible limitation.

Both Johansson et al. and de.wiki use overlaps between different categories. It is well established in de.wiki that there is a halogen category and a metalloid category, most elements in these groups are not defined as anything other than halogens and metalloids, respectively. We have decided we should handle those cases by putting all elements into one group or another. Having to have a group that entirely falls into another group is something neither Johansson et al. nor de.wiki do. Perhaps somebody does, but it doesn't matter: if someone uses this kind of overlap, it doesn't mean we should. It would be beneficiary if we had established the importance of having to have an element in two groups. As I said, no such case has been shown and I don't believe there is. I regard all subcategories as not needed. If we do want to show this knowledge, we can very well do that in our articles, not in a first-level classification.

I am not convinced by the arguments in favor of the new nonmetal division per se, but I will not at this moment argue against them, mostly because I am myself not sure whether a division of reactive nonmetals could be an overall positive thing or not. The strongest argument in my head in favor of this division is that it brings back the term "halogen" into the fold, however, I'm afraid that people will assume that "halogen nonmetal" is tautology even while noting that At is not a part of the scheme. I know that, strictly speaking, there is no problem of definition, but I am afraid this name will be misunderstood and cause more confusion than there should be. I have not made my mind about that yet.

I think the term "light metal" merits a consideration based on its popularity. No question about that.

What is a light metal, precisely? If you asked me, I'd say, "it's a metal with a density of less than 5 g/cm³." That's the definition I think of when I think about this term. The problem with it is that it's not a good definition to classify chemical elements: it is about physical properties, not chemical ones. All other category names are based on chemical properties of those elements that constitute those groups. It hadn't even crossed my mind we could be considering a not-chemistry-based category names. Second, what elements would constitute that group? I think of titanium as of a light metal, and the proposed category name does not match my expectations when it comes to its constitution. That would leave me puzzled. The existing category names cause no confusion whatsoever. It is clear to me that after a consideration, having "alkali metals" and "alkaline earth metals" is a better option. I suggest we do that.

"R8R has expressed support for two nonmetal categories" -- I want to be clear about what I said, I have expressed conditional support, and the condition is that we have two good category names to use. I am still pondering whether the condition has been met. I can't say off the top of my head that it has not, but I can't say it has, either.--R8R (talk) 09:47, 26 September 2020 (UTC)

@Sandbh: I apologize for taking so long to reply. It takes me quite some time to write such long responses down and I can't always find it on working days. It is likely I may have a problem doing that in the future, too, though I'll try to respond more quickly.--R8R (talk) 09:54, 26 September 2020 (UTC)

YBG comments

@R8R, YBG, DePiep, and Sandbh:

A few quick comments after a quick read-through of Sandbh's latest post.

• We do not show [Halogen] since ...

  On the contrary, we do show halogen as a group, just not as a category.

• IUPAC does not endorse noble metals as category.

  As I understand it, all IUPAC does is endorse named lists of elements. "Category" is term with a specific meaning at enwiki and it would be best not to confused things by using it in other ways or in ambiguous ways.

• The frequency with which Groups are not flagged is remarkable.

  I'm not entirely sure what you mean by "flagged". But all periodic tables are designed to show periodicity by placing groups in columns. They may or may not be labeled, but they are always displayed. It's what makes a periodic table "periodic".

• Light metals is fourteen times as popular as post-transition metals and reactive nonmetals, both of which we show.

  As I've mentioned elsewhere, I am very skeptical about using popularity this way. Frequency of occurrence is useful to determine what name to use for a particular element, or what elements should be included in a particular collection. It would also be useful to compare the frequency of different systems of categorization, but this cannot be determined by simplistic ngram comparisons.

YBG (talk) 06:07, 22 September 2020 (UTC)

@YBG: Yes, I agree about halogen. The WP PT showed it as a colour “zone” for ten years.

“Flagged” means to mark something in order to draw attention to it.

According to the COPTIC database the most popular categorisation scheme is either metal-metalloid-nonmetal (8%) or Ln-An (8%). The average number of categories is ~4½, within a range of 0 to 9. The 62 schemes are diverse.

Following the literature, the WP colour category table would just show metals; metalloids; nonmetals; Ln and An. That is not so informative. TMs merit a guernsey, as do NGs. That leaves the s-block; the metals between the TM and the metalloids; and the nonmetals between the metalloids and the noble gases. At this point, and in terms of the literature, the ngrams then have their place. Sandbh (talk) 13:30, 22 September 2020 (UTC)

re Sandhbh: I don't understand 'guernsey' here. re The WP PT showed it as a colour “zone” for ten years: true and trivial. (but why use "zone" out of the blue? Is that different from category?). Anyway, that discussion is available. I have not read a single argument against it recently but lamentations and qualified popularity claims. Also a Venn-category ("nonmetal halogens") is proposed for similar absent reason. And, of course, the set name halogen is already in use. -DePiep (talk) 15:58, 23 September 2020 (UTC)

@DePiep: Meriting a 'guernsey' means you are on the sports team, and get to wear a top with the team colours on it. I used "zone" as a vanilla way of referring to a set of elements without necessarily being concerned about whether they are a formal Group, or a category. For example, the end zone in American Football, or a red zone as a loose name for any area of concern. If I understand you right I am not proposing a Venn category spanning the nonmetals. Rather, I am proposing two sub-categories of reactive nonmetals: 1. Reactive (pre-halogen) nonmetals; and 2. Reactive (halogen) nonmetals. In other words, something along the lines of "Colour category PT: Proposal 2", below. Sandbh (talk) 00:14, 24 September 2020 (UTC)

Taxonomic periodic table

Colour category PT: Proposal 1
The 18-column form of the periodic table, with a placeholder between groups 3 and 4 for the lanthanides and actinides

---

A detailed interactive version is found in § Overview below; an interactive 32-column form, after § External links.

@R8R, YBG, and DePiep: Further to the previous section, here is draft table for the lead of our periodic table article, followed by the current version.

I have temporarily abandoned the rare earth category. It seems like too much bother. Sandbh (talk) 02:50, 22 September 2020 (UTC)

@R8R, YBG, and DePiep: The third version retains the categories we have now. The intensity of the red shade for the AM has been toned down. The noble metals are denoted by a carat symbol. The pre-halogen reactive nonmetals are each flagged with a degree symbol = a circle of life; the associated note mentions alt-names found in the literature. The Group 17 marker has a dagger-note referencing F to I as halogen nonmetals. Sandbh (talk) 11:39, 22 September 2020 (UTC)

The circle further corresponds with the catenative tendencies of the nonmetals involved. Sandbh (talk) 23:00, 22 September 2020 (UTC)

Colour category PT: Current version
The 18-column form of the periodic table

---

A detailed interactive version is found in § Overview below; an interactive 32-column form, after § External links.

Colour category PT: Proposal 2
The 18-column form of the periodic table, with a placeholder between groups 3 and 4 for the lanthanides and actinides

---

A detailed interactive version is found in § Overview below; an interactive 32-column form, after § External links.

Colour category PT: Proposal 3
The 18-column form of the periodic table, with a placeholder between groups 3 and 4 for the lanthanides and actinides

---

A detailed interactive version is found in § Overview below; an interactive 32-column form, after § External links.

What grams are good for - and not

Imagine for a moment that we are not categorizing elements but some portion of the animal kingdom. Imagine further that there are no biologists talking about this issue. Implausible, I know, but bear with me.

At issue is whether we should have separate categories for platypus and echidna -- or a single category for monotremes.

What do the google grams tell us? Check it out here.

Platypus and eckidna are way more popular than monotreme, so of course we have two categories, not one. Right?

No, that is absurd.

Likewise, it is absurd to use ngrams to decide whether to combine AM & AM.

What good then are ngrams? Well, if we do decide to merge two groups into one category, it might be useful in deciding a name, by using something like this ngram. Of course one would have to determine if "active metal" is being used in the sense intended. And one would need to figure the right way to encode pre-transition. But i hope you get the point. Ngrams may help us decide a name of a category, but not whether something should be a category.

YBG (talk) 08:09, 12 September 2020 (UTC)

I see your point. While I don't disagree with it generally, I'd like to point out that I would not have brought up Ngrams if there were not enough difference, like in the case you mention. "Platypus" is ten times more popular than "monotreme" (based on the 2019 data) and "echydna" 3.5 times, which to me is a sign that the amount of occurrences of "monotreme" is not negligible. The difference between "alkaline earth metal" and "pre-transition metals" is three orders of magnitude, not one---that's a big difference and I'd say, it's telling enough.

I see "pre-transition metals" as a generic term. We also have other generic terms, say, "post-transition metals," so it's possible to have another in principle. However, "post-transition metals" has no non-generic alternatives whereas "pre-transition metals" does, and on basis of that we shouldn't add "pre-transition metals" to our fold of categories. That was my initial hunch to check Ngram, and I'd say I have my hunch confirmed as convincingly as that tool could.--R8R (talk) 09:19, 12 September 2020 (UTC)

re YBG. I greatly enjoy the more abstract, maybe mathematical, approach (met more than once here). I find it amusing (not really, worrying actually) that this thread refers to "popularity" of a wording. As if that is going to be an argument, or source even (I mistyped: artgument. lol). What happened to finding RS for a claim? As for tallying, this is the furthes we can go I'd say.

Then zoom out: in what discussion is this brought up? If I am reading all this right, renaming and reorganising categories. (Another weird approach I find: somehow trying to merge groups and categories; for & by their names even. Ouch for such aim).

In general: if a category is related internally strong, and externally weak: good. -DePiep (talk) 21:10, 12 September 2020 (UTC)

Allow me to add yet another reason I am skeptical about using ngrams to decide whether a particular collection of elements should be considered an enwiki category.

By ngrams alone we cannot determine much about the context. As DePiep concisely said, the relationship or similarity between elements of a category to other elements should be internally strong, and externally weak. There are three things we need to note about a collection to help us in this.

1. What elements are being discussed? In some cases this is trivial; in others, it requires a meta-analysis such as that at Lists of metalloids.
2. How are the internal similarities described? In particular, how strong are they?
3. How are the external comparisons described? In particular, what other collections are contrasted?

For example if we are wondering about the noble gasses, 1 and 2 are fairly obvious, but 3 is telling. In discussing the NG, does an author merely compare and contrast them to other groups? Then the article is discussing the NG as a PT group. But if an author compares the NG to larger collections of elements or even all other elements, then the article is discussing the NG as a higher level of the taxonomy, eg, as what we at enwiki call a metallicity category.

What about the AM (or AEM)? Again, 1 and 2 are obvious, but 3 interesting. If an author contrasts the AM (or AEM) to groups like the NG, AEM/AN, or group 3, then the author is discussing the AM (or AEM) merely as a group. Only if the author compares the collection to larger collections that are bigger than groups would I be willing to say the author is treating the AM (or AEM) as more than just a group, as something at a higher level of the taxonomy, like our enwiki metalicity categories.

My main point here is that such information - which I submit is critical for whether we should consider a group to be not just a group but also a metalicity category - such information cannot be deduced from ngrams.

This is hopefully a better and more complete explanation than my discussion of Australian megafauna above.

-- YBG (talk) 07:53, 21 September 2020 (UTC)

@YBG, DePiep, and R8R: From my reading of the literature, external comparisons of sets of elements is uncommon. That is due to the established existence of meta-properties such as metallic; nonmetallic; IE; EA; EN; standard reduction potentials; outer sub-shell configurations; differentiating electrons; and crystalline and molecular structures. There is no intrinsic need to compare or contrast sets of elements, since any particular set of elements can be implicitly placed within the overall scheme of things by reference to these properties without the need for benchmarking with other sets of elements.

@DePiep: Your category-fidelity criterion of related internally strong, and externally weak appears to have merit. The AM and AEM don't warrant a category, given the strong external relationship the AM and AEM have with one another:

TABLE A: Category-fidelity check for sets of chemical elements

Set	Internally strong?	Externally weak?	Notes	Attributes
AM	✓	❌	Quite similar to the AEM	Mostly strongly electropositive, with a few of the light An (U to Am) being only moderately electropositive.
AEM	✓	❌	1. Quite similar to the AM 2. Be is an outlier 3. Mg is not an earth
Ln	✓	~	Chemistry quite similar to AM and AEM
An	✓	✓ ❌	1. Early AN closer to period 6 TM analogues 2. Late AN virtually the same as Ln
TM	✓✓	✓	Ag is an outlier with a predominately main-group chemistry in its preferred +1 oxidation state	1. Moderately to weakly electropositive in nature 2. A small number, such as Zr, are more strongly electropositive; several others are chemically very weak (or noble), like Pt, with these representing the noble metals
PTM	✓	✓	Al is an outlier; categorically, per Deming, it is closer to Be than to the PTM (or Sc)	1. As a set, adjacent to the frontier territory between the metals and nonmetals 2. Most of them, such as Sn and Bi, are chemically weak; a minority are moderately electropositive (Zn, for example) 3. Being near the non-metals, their crystalline structures tend to show covalent or directional bonding effects, having generally greater complexity or fewer nearest neighbours than other metallic elements
Metalloid	✓	✓	Based on normalised values of IE, EA and EN, B is the most metallic metalloid; Te is the most non-metallic	1. Sub-metallic appearance; all known in semiconducting forms 2. Weakly nonmetallic chemistry; their oxides are weakly acidic, or amphoteric 3. Organic compounds of the metalloids fall within scope of the definition of organometallic compounds, as a long-standing tradition
Orphan nonmetals	✓✓	✓	1. Oxygen is an outlier in a few respects e.g. M oxides are usually ionic 2. Based on normalised values of IE, EA and EN, P is chemically the weakest orphan nonmetal; O is chemically the most non-metallic	1. Sandwiched between the strongly electronegative halogen nonmetals and the weakly nonmetallic metalloids, their physical and chemical character is overall moderately non-metallic 2. Sub-metallic, coloured or colourless appearance; a brittle comportment if solid (including black N) 3. Overall tendency to form covalent compounds featuring localized and catenated bonds as chains, rings, and layers 4. Prominent geological, biochemical (beneficial and toxic), organocatalytic, and energetic aspects 5. Marked dualistic character; unified in their diverse yet shared attributes
Halogen	✓✓	✓	A classic contrast to the AM-AEM	Characterised by coloured appearance and acridity, and uniformly high values of IE, EA and EN
NG	✓✓	✓✓	Rn, which shows cationic behaviour, is an outlier	Characterised by invisibility and torpidity

--- Sandbh (talk) 01:39, 23 September 2020 (UTC)

Halogens

I'm unconvinced of the helpfulness of separating out the halogens .... they already are grouped together. Similarly, I don't see the advantage of having alkaline metals and alkaline earth metals as full-blown categories .... they already have recognition as groups. Thus, I'd have a reactive metal category. I know that the same logic could also be used to preclude a NG category, but if any group is unique enough to be distinguished as a full-blown category, it is the NG.

As to OR, yes, all of these things are attested to in the literature, but there are many, many categories in the liturature, not just the ones we've chosen. Where we come close to the line is in our elevating one particular scheme of mutually exclusive and jointly exhaustive categories to the prominence of our infoboxes. On balance, I think it is ok but I can respect those who think we've crossed the OR line.

YBG (talk) 06:38, 9 August 2020 (UTC)

​Well, the traditional aspect of teaching the periodic table is to contrast the alkali metals with the halogens. So that'd be a relatively strong consideration.

This supports keeping the alkali metals, and separating out the halogen nonmetals noting the focus on the latter is always fluorine, chlorine, bromine, iodine. We did not do this with our current table. IIRC that was because we weren't able to satisfactorily characterise the other nonmetals as something other than {other nonmetals}. So we decided that they and the halogen nonmetals would collectively be the reactive nonmetals.

Going back to our first ever periodic table, there certainly are lots of categories in the literature. The chosen colour categories were an outcome of a discussion in WP:ELEMENTS based on the most popular categories seen in the literature, with some hand-waving and confusion when it came to the leftover nonmetals. The latter train-wreck, as seen in the literature and the eight different categorisation schemes seen in our nonmetals article, resulted in the {other nonmetals} category, as there didn’t seem to be anything better at the time.

In our endeavours to nail the other nonmetals we've now gone full circle from {other nonmetals and halogens} → {polyatomic nonmetals and diatomic nonmetals} → {reactive nonmetals}. Now we have a putative YBG-rules-compliant categorisation scheme for going from {reactive nonmetals} → {coactive nonmetals and halogen nonmetals} that would fulfil the worthy intent of our predecessors.

The remaining consideration is that while the characterisation involved is robust, the actual descriptive category label {coactive nonmetal} is not recorded in a reliable source. Not yet, anyway.

On the mini-table seen in our info-boxes, I find the colour scheme to be a helpful navigational aid. Richey et al. (2010), writing on learning theory, support the use of colour to differentiate ideas and direct attention to key topics.

Richey, R.C., Klein, J.D., Tracey, M.W.: The instructional design knowledge base: Theory, research, and practice. Routledge, New York (2010)

--- Sandbh (talk) 23:38, 9 August 2020 (UTC)

The traditional pedagogy contrasting halogens with alkali metals says nearly nothing about the question at hand because both are groupa. A desire for consistency in our categorization does make that argument, but consistency could equally be used in favor of a reactive metals category. I strongly believe that only the noble gases are deserving of a monotypic category. It seems to me that one fewer category would make our system would be better pedagogicallly, better esthetically, better taxonomically, and better mnemonicly. Of course, when you discuss a given category, it would make sense that you begin by a group-by-group discussion. If such an approach works for the transition metals, then why not for the reactive metals and reactive nonmetals?

As a separate issue, we could reduce the number of categories by one more by adopting the term inner transition metals. This would have another advantage in eliminating the only horizontal boundary line. Its not quite as bad as summer time zones in Australia, but ...

In short, our current nine categories is quite unwieldy being at the extreme limit of the magic number 7±2. Increasing it to ten is really too much, going in the wrong direction. I'd much rather see us go to eight or even seven.

--- YBG (talk) 04:55, 10 August 2020 (UTC)

PS check https://colorbrewer2.org to see how much more flexibility we have with fewer categories. YBG (talk) 05:13, 10 August 2020 (UTC)

@YBG: There is hope. I don't know how other members would feel about it:

               Noble gases
               He to Rn
Active metals           Halogen nonmetals
Groups 1-3, Ln, An      F to I
Transition metals       Coactive nonmetals
Most of them            H, C-O, P-S, Se
Post-transition metals  Metalloids
Ag, Sn, Bi etc          B, Si, Ge, As, Sb, Te
               Noble metals
               Ru, Rh, Pd, Os, Ir, Pt, Au

Eight categories. Symmetrical relationships. These can facilitate learning since fewer observations are required to describe the applicable system. Further, concepts that possess symmetry can be more easily grasped than those that do not (Randall 2006).

"Active metals" is in the literature. The noble metals are a subset of the transition metals (MacKay et al. 2018; Rayner-Canham 2018). I presume we will want to retain the popular notion of the metalloids being an intermediate category. That is fine. We can simply note that it has been known for over 120 years that metalloids have a predominately nonmetallic chemistry (Newth 1894; Friend 1914).

All categories meet the YBG rules. Note this is a consistently non-Group approach. That said, we additionally list the Group names along the top of each group as we do in the main body periodic table of our article of the same name. Ditto, we include the category names lanthanoids and actinoids to the left of the respective rows, as we used to do.

Winners all round. Eight consistent categories. Simpler colour scheme. No more tears over categorising nonmetals.

I note in the past we rec'd an objection to removing the alkali and alkaline earth categories.

PS: When discussing a category, you can start at the category level and examine its shared characteristics. Then you could examine the 18 groups from L to R (presumably) so you can track, among other things, the transition in metallic to nonmetallic behaviour. As well, where relevant you can examine the groups within each category. Much flexibility as to approach.

• Friend, J.N.: A Text-book of Inorganic Chemistry, vol. 1. Charles Griffin and Company, London, p. 9 (1914): "Usually, the metalloids possess the form or appearance of metals, but are more closely allied to the non-metals in their chemical behaviour"
• MacKay, K.M., MacKay, R.A., Henderson, W.: Introduction to Modern Inorganic Chemistry, 6th ed. Nelson Thornes, Cheltenham, p. 204 (2002)
• Newth, G.S.: A Text-book of Inorganic Chemistry, pp. 7 − 8. Longmans, Green, and Co, London (1894)
• Randall, L.: Warped passages: Unravelling the universe’s hidden dimensions. Penguin Books, London, p. 193 (2006)
• Rayner-Canham, G. Organizing the transition metals. In Scerri E., Restrepo G. (eds.) Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table. Oxford University Press, New York, pp. 195–205 (2018)

--- Sandbh (talk) 06:40, 10 August 2020 (UTC)

So I'm trying to draw the periodic table with these color schemes. I have two questions. First, where does copper go? Transition metal I assume, but based on its position, it seems that it might be a post-transition metal. Second, what happens after bohrium? Is hassium a transition metal or a noble metal? Meitnerium? Copernicium? Oganesson? ― Дрейгорич / Dreigorich Talk 03:43, 11 August 2020 (UTC)

@Дрейгорич: Nothing else changes compared to our current table. Cu is TM, as are Bh and Hs. Anything after that is unknown properties. Sandbh (talk) 11:51, 11 August 2020 (UTC)

@Sandbh: Ah. Curious why hassium isn't considered as one of the noble metals then. It's right below osmium, which definitely is a noble metal. Hassium should be even more so of a noble metal. Or does the trend break down? ― Дрейгорич / Dreigorich Talk 14:56, 11 August 2020 (UTC)

@Дрейгорич: I suspect the reason why Hs isn't considered to be a noble metal is that we haven't so far had a way of flagging elements to show their predicted categories e.g with a circumflex^. If we did then I'd suggest Hs = noble^; Mt = transition metal^; Ds-Rg = noble^; Cn, Nh = unknown; Fl, Mc, Lv, Ts = post-transition metal^; Og = unknown. Sandbh (talk) 00:53, 12 August 2020 (UTC)

PS: I suggest colouring the noble metals the same as the transition metals. See here for an example of what I mean. Sandbh (talk) 00:58, 12 August 2020 (UTC)

@Sandbh: Huh. Any reason Mt isn't likely a noble metal? I think it would be a denser, super-radioactive version of iridium pretty much. Is there something in its chemistry that's predicted to stop it from being a noble metal? ― Дрейгорич / Dreigorich Talk 01:01, 12 August 2020 (UTC)

@Дрейгорич: Yes. Meitnerium is expected to about as noble as silver (the standard electrode potential for the Mt³⁺/Mt couple is expected to be 0.8 V, close to the +0.7993 V value known for the Ag⁺/Ag couple). Rayner-Canham (2018, p. 205) in, "Organizing the transition metals" says, "This author would contend silver is so much more chemically reactive…that it should not be considered as a 'noble metal.' " Sandbh (talk) 02:05, 12 August 2020 (UTC)

Huh. A minor surprise then. Didn't know that. Thanks for helping me learn something new. ― Дрейгорич / Dreigorich Talk 02:08, 12 August 2020 (UTC)

@Дрейгорич: Works both ways, coactively if you will. I think I learn something new just about every time someone posts here. Sandbh (talk) 05:24, 13 August 2020 (UTC)

Coactive terminology in the literature

About the term coactive nonmetal, the complementary term "coactive metal" is found in literature in the following senses:

• "…adding a coactive metal (such as Pt, Ir, or Rh metal)"
• "The same set of experiments was performed in presence of other co-active metal ions Fe ⁺², Fe ⁺³, Co ⁺², Ni ⁺², Mn ⁺², Cd ⁺², Ca ⁺², Mg ⁺²…".
• "It is of great interest and challenging to improve new catalysts that consist of any of those components and new active metal component (ie co-active metal, promoter)."

There are several other references in the literature to "co-active" elements, materials or substances, including manganese, iron, nickel, cobalt and plutonium.

It further transpires there is a field of organocatalysis that uses small organic molecules predominantly composed of C, H, O, N, S and P to accelerate chemical reactions. So there is nice overlap between organocatalysis, coactive nonmetals, and the {biogens} category of nonmetals.

Summarising, the coactive nonmetals are distinguished by their:

1. moderate net non-metallic character;
2. covalent or polymeric compounds;
3. prominent biological roles^¶;
4. proclivity to catenate i.e. form chains or rings;
5. multiple vertical, horizontal and diagonal relationships;
6. uses in, or as, combustion and explosives;
7. uses in nerve agents;
8. uses in organocatalysis; and
9. dualistic Jekyll (#2) and Hyde (#5−6) behaviours, thus, "coactive" ^_^

¶ such biological chemistry being only understandable in terms of the symbiotic use of the nonmetals involved, "symbiotic" meaning "characterized by or being a close, cooperative, or interdependent relationship" (c.f. "coactive"): Williams RJP 1981, The Bakerian Lecture, 1981 Natural selection of the chemical elements, Proc. R. Soc. Lond. B 1981 213, 361-397 (361, 396)

Is "coactive nonmetal" a neologism or is it a descriptive phrase, c.f. "coactive metal"? If there are coactive metals does this suggest there are coactive nonmetals? The other nonmetals category is well enough seen in the literature. The covalent-polymeric, biological, catenative, combustive/explosive, and organocatalytic properties of the nonmetals in this part of the periodic table are documented in the literature. Historically, the "other nonmetals" category is the most enduring nonmetal category used in the Wikipedia periodic table, until we started complaining about what a non-informative category name this was. Do we now have enough content, in pursuit of a better encyclopedia, to support a change back to a binary categorisation of the nonmetals as coactive (formerly other) nonmetals, and halogen nonmetals? I'll ask around. --- Sandbh (talk) 01:33, 10 August 2020 (UTC)

@Sandbh: I don't quite understand whether you propose a change for a new category scheme to be used now in en.wiki or not. I personally thought that this section started as a series of lighthearted jokes (I didn't have much to add but I liked how everyone was having fun) and have trouble understanding what it has evolved into since. Are you proposing a change or are you thinking out loud? I'd like to formulate my opinion, too, but for that I would need to understand what it is that I am to formulate my opinion about.--R8R (talk) 16:14, 10 August 2020 (UTC)

@R8R: Yes, I'm pitching a change to our scheme from reactive nonmetals, to coactive nonmetals and halogen nonmetals. It's funny how these things get started. You'll remember the other nonmetals saga, which resulted in our current scheme. At the time you said, "I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one." We now have such a divide with two clear self-descriptive relevant terms.

A consideration is that the adjective "co-active" is found in the literature as part of the phrase "co-active metals". But the phrase "coactive nonmetal" isn't. The closest we get is that coactive nonmetals have (organo-)catalytic applications; that coactive is a synonym for catalytic; and that coactive encompasses the various other synergic aspects of the coactive nonmetals. Oh, and it is pleasing that in going from reactive to coactive requires only two letters to change, by no more than three places in the alphabet.

One of the meanings of "other" is "existing besides". Synonyms for "besides" include "in conjunction with", (here conjunctive means, "relating to or forming a connection or combination of things"); conjointly"; and "jointly". So there is a pleasing link to the nature of the nonmetals in question.

See also my response to Dirac66, hereunder. Sandbh (talk) 07:47, 11 August 2020 (UTC)

I see. In that case, I will recall that my opposition back when we were establishing the term "reactive nonmetals" was based on that there was no well-known term to describe the division within the nonmetals other than the noble gases. In the absence of that, "reactive nonmetals" was the next best thing because it was fairly descriptive: these are nonmetals that commonly engage in chemical reactions, as opposed to the noble gases which don't. The word "reactive" is a part of the common language. A well-established term would be better but there isn't one, so we have to settle on that.

I am uneasy about the term "coactive metals". The thing is that I had never head the word "coactive" prior to this discussion and I thus didn't know its exact meaning, although I could guess. After writing this message, I genuinely had to check what this word meant. I take my own words with a pinch of salt since I am not the most potent English speaker, but I see that Dirac66 has similar concerns below.

So after (again, unironically) checking what the word meant, I learned it meant "acting in concurrence or together." With this knowledge in mind, I find it difficult to imagine that it will be easily understandable what the term means. I wasn't able to guess (which is worrying, too) but I just re-read the above to understand what was meant here. And unlike the rest of the terms (like "alkali metals" or even "reactive metals"), this term is not even about chemistry per se, which makes it rather doubtful that we want to use it as a part of the primary classification of the chemical elements. To me, these considerations are a deal-breaker.

I also think that "halogen nonmetals" is a rather deceptive term. We normally think of the halogens as of nonmetals, and I think it's going to be fairly common for common readers to not see the point why it can't be just "halogens." However, it can't, so the source of confusion is here to stay (yes, we can describe it but many people people won't click the link to find the explanation; they may not even guess a description is to be found behind that link). I think that bringing confusion isn't good for the purpose of having an encyclopedia for a common reader.

I think it's a fair attempt to renew our classification, but I'm afraid it's not fit for our purpose. That being said, this is not to say it can't be used at all (though I'd still be weary of having to intersect two independent terms "halogen" and "nonmetal" to get one).--R8R (talk) 15:25, 11 August 2020 (UTC)

@R8R: Thanks, it was a bonus to read your assessment that it’s a fair attempt to renew our classification. Things can only get better from there.

I'll attempt to carefully address your concerns.

1. No well established term for the division. That is not our concern. We have to deal with the literature as is. The most popular term is other nonmetals.

2. The term coactive is not understandable. Why are we applying a higher standard in this case? I agree, coactive is not a common term. Neither are alkali, alkaline earth, lanthanide, actinide, post-transition, and metalloid for our target audience of common readers. That is where wiki-links come into play. I do not concern myself if a common reader does or does not choose to click on a link.

3. Not about chemistry. The term "coactive" is found in the chemistry literature. It refers to catalysis. So, coactive nonmetals have (organo-)catalytic applications; coactive is a synonym for catalytic; and coactive encompasses the various other synergic, chemistry based aspects of the coactive nonmetals.

There is a further pleasing link to the nature of the nonmetals involved in that a subtle meaning of "other" is "existing besides". Synonyms for "besides" include "in conjunction with" (here “conjunctive” means, "relating to or forming a connection or combination of things"); “conjointly"; and "jointly".

4. Halogen nonmetals is rather deceptive. Common readers will not know what halogens are. On halogen nonmetals, this term is found in the literature. Common readers will not know this. They will have no reason to wonder why we don't just say halogens, in the same way we don’t just say alkaline earths.

*     *     *

The real issue, as I see it, is a gap in classification science terms. So, after applying the most popular categories found in the literature to the periodic table, what is leftover for the remaining nonmetals is other nonmetals.

Whereas a category name would normally be descriptive, other nonmetals is a non-defining-characteristic name.

In summary, while the category concerned already exists it's let down by its non-defining-characteristic name. It seems like a small step from "other" to "coactive".

All the properties of interest are set out in the literature, as is the "other nonmetals" category. Other nonmetals seemingly means nothing meaningful; coactive nonmetals may be unfamiliar but is rich with meaning.

It'd be funny to return to other nonmetals, which we should, since this is the most popular name for nonmetals in this part of the periodic table. I see no grounds for not doing so.

We do have a better descriptive phrase now, however. --- Sandbh (talk) 07:43, 12 August 2020 (UTC)

I have seen and read your message; not sure when I'll be able to write down a response; my apologies in advance in case I'm not able to do so quickly.--R8R (talk) 12:52, 13 August 2020 (UTC)

@R8R: I'll see if I can get around to drafting a nonmetal article based on other nonmetals, halogens, and noble gases. For the "halogen nonmetals", the oldest use of this term I've seen so far is from an 1885 Chemical News article. --- Sandbh (talk) 07:28, 14 August 2020 (UTC)

Here comes my response.

I suppose that we may ignore points 1 and 3 for now. My mind has been off this topic for a while now, and I can't be certain you're correct, but I can't claim the opposite, either, so I don't oppose those responses. Generally, this is why I offer myself as a sort of sanity check rather than a side of a discussion; the same also went for the last group 3 debate.

My greatest concern is point 2. I have been consistent about how there should either be a common term in the field or, in the absence of that, a term intelligible to a common English speaker. Say, "alkali metal" is very common; you learn it during the first year of your school chemistry classes. Same goes for AEM, Ln, An, TM, metalloid, and the noble gases. (The term "halogens," for that matter, would also fall into this category, and I assume this is why it was used in our classification for so long.) The term "post-transition metal" is intuitive for an English speaker (a metal that comes after a transition; it is precisely so, there is a transition to come after, and a metal in this category comes precisely after the said transition). What's left is the set of the non-noble nonmetals, which I suggested we define as "reactive nonmetals"---nonmetals that react (which, in fact, they do). We don't use the term "other nonmetals" solely on the account of its meaninglessness---you need to define the other terms first to see what's left.

I disagree that what the way I evaluate the suggested term is a higher standard. The standard has been the same. The term "coactive" doesn't appear to be understandable. I'd have my own reservations about this conclusion because it came from myself and I'm not the best English speaker out there---I learned the word "detergent" today, for instance---but another editor, whose English is probably better than mine, has said they hadn't heard it, either. Does it maybe somehow qualify as a professional term? I'm actually very willing to ask our fellow editors from WP:CHEM or WP:CHEMS to see what they have to say; I suspect that I'm right in my scepticism but I feel I can't claim that, so I'd gladly ask for more opinions. What would you say?

As for point 4. I assume that the common reader will know what a halogen is. It's an important consideration for me since I always try to have common readers in mind, so I'll expand on this.

The common reader I have in mind is a person who knows the very basics and that's pretty much it. The said basics of chemistry do include the term "halogen." I always write myself trying to make my texts as understandable as possible, but this sometimes requires too much explanation if I assume that the read doesn't know anything, and the complete explanation simply doesn't fit, so it turns out I have to assume some knowledge of the reader (or say that an article is not for them). In fact, the last time we had a discussion about this, you suggested I don't include an introduction to the superheavy elements to all respective articles because that's rather offtopic. Presumably you expected the common reader to know what the introduction had to say or say that the article wan't for them? What's the difference between that case and this one?

I also think that assuming that the common reader knows nothing we talk about anyway and all terms are on an equal footing is rather a disservice for the common reader. Some terms are better known than others. Even if they don't know them, they can look them up. If they won't look anything up, then they better learn a term they could say to someone who understand more and not hear in response, "never heard that term, where did you hear that?" We could deviate from this idea in principle if we weren't an encyclopedia that is meant to be a tertiary source.

coactive nonmetals may be unfamiliar but is rich with meaning -- that would be a fine rationale if you were to write your own book and you were thinking what terms to use. In Wikipedia, however, "unfamiliar" compounded with "uses a word that is uncommon in general" is a problem.--R8R (talk) 16:22, 15 August 2020 (UTC)

@R8R: Thank you.

Common reader. I take the common reader to be one of the people I meet on a day-to-day basis. Neighbours, friends, former work colleagues, coaching clients, social contacts, family. People who, these days, punch an unfamiliar term into WP rather than, as occurred in the old days, look it up in a hard copy dictionary. One of my neighbours is a chemistry teacher and he knows what I talk about. All the rest look at me dumbfounded. They usually recall what a periodic table is. Anything deeper than that is beyond them. Nonmetal—eh? Metalloid? Never heard it. Halogen? What's that? And so on.

The term coactive is not understandable. The word "coactive" is simple. It is made up the common "co-" prefix and the plain English word "active". Hence, for example, coaxial, co-operate, coauthor. I don't know of a simpler descriptive word for the orphan nonmetals. The word detergent, on the other hand, is not understandable. I would not know how to break if down (de-, tergent; what's a "tergent"(?); deter- gent?), although I know its meaning.

WP:MOSWTW says:

”Adding common prefixes or suffixes such as pre-, post-, non-, anti-, or -like to existing words to create new compounds can aid brevity, but make sure the resulting terms are not misleading or offensive, and that they do not lend undue weight to a point of view."

There is WP:NEO too, but that is about articles, not articles setting out concepts. Here I mean that the content on other nonmetals, or coactive nonmetals, will form a section of our nonmetal article, as we do now, not an article of its own.

Ask our fellow editors from WP:CHEM or WP:CHEMS Yes, I did this to test the water. I asked eight of them. Out of five responses, four raised concerns about WP:NEO; one, Dirac66, was concerned about WP:OR and asked why there is a need to change from the set {other nonmetals-halogens-noble gases}.

As I noted, WP:NEO does not apply here. Nor does WP:OR. The other nonmetal category exists in the literature. All the properties of interest are set out in the literature. No new ground in chemistry will be broken. The meaning of coactive is supported by reliable sources. The subject matter is notable.

An introduction to the superheavy elements to all respective articles. I suggested not including an introduction to this for the same reason we don't have an introduction to metals at the start of all respective articles. One can click on the first metal wikilink, for example. I recall suggesting the use of a hatnote, too.^ That is not the same as what I am trying to do here. Further, there will not be a coactive nonmetal article. The subject will instead be included in the nonmetal article, as we do now (we have no reactive nonmetal article; rather, the term links to the relevant part of the nonmetal article).

^ try looking up hatnote, hat note, or hat-note in the Oxford English Dictionary—you won't find it

^     *     *

I recall you supported a binary division of the non-noble nonmetals. We went with reactive nonmetals as we could not find a suitable term for the non-halogen nonmetals, aside from "other nonmetals", which nobody liked due to its meaningless nature. Well, now we have a suitable descriptive term.

"Other nonmetal", which by rights we should be using, is uncontroversial but uninformative. The logical alternative of "coactive nonmetal" is fully informative and encompassing, and does not breach WP policy. It may cause cause a ripple of excitement for unproductive and unfounded reasons—reasons that do not fundamentally have anything to with building a better encyclopedia. By "encyclopedia" I mean a reference work or compendium providing summaries of knowledge from all branches, rather than a reference work missing some summaries due to needless terminological confusion.

I think I've addressed all your concerns. Please let know of your thoughts. --- Sandbh (talk) 06:04, 16 August 2020 (UTC)

Again, I apologize but my response probably won't be very quick.--R8R (talk) 18:01, 18 August 2020 (UTC)

@R8R:. Sandbh has abandoned "coactive nonmetal" as a category name, now preferring "pre-halogen nonmetal".YBG (talk)

@YBG and R8R: Sort of abandoned. In my head it's like other metals → post-transition metals → frontier metals. The corollary is other nonmetals → pre-halogen nonmetals → coactive nonmetals. Sandbh (talk) 01:01, 19 August 2020 (UTC)

Term succession

@Sandbh: Although I see the name "coactive metals" has been abandoned, I still think it may be useful to reply to Sandbh's previous points. The usefulness may be in sharing the thinking why I pass judgment on different names one way or another.

Common reader: While I agree with what you're saying here, it is still not useful to those readers who will read the article as to people who have no clue about chemistry in general. First of all, my general assumption is that it's likely you have at least an interest in chemistry or some sympathy to it if you're really going to read an article on a grouping of elements or a Chemistry section of an article on an element. The term "common reader" in this context refers to people who don't have much beyond that but who do have that much. Second, while the said common reader is the primary audience, there is also the need not to have professionals scoff at what we write. If they all turn in saying they had never heard a term, then that term is a no-no. The way out of this, as I have mentioned, is descriptory phrases. I think it's easy enough to see how "post-transition metal" is such a phrase. The same goes for "reactive nonmetals" if you note that the only other category of nonmetals is the set of noble gases, which are famed for being unreactive. I doubt the same goes for "coactive metals."

The term coactive is not understandable. I sustain it is not, at least not for me. While the etyomology is clear from the mere look at the word (co- + active), the same does not necessarily goes for its meaning. Whereas the word "coauthor" is easily seen as the sum of co- and author, I've never thought the same way about, say, the word "cooperation." As one way out of this confusion, I'd suggest you try to explain in one short phrase what the term means by referring to the words used in it. A "post-transition metal" is a metal that comes after a transition. A "reactive nonmetal" is a nonmetal that commonly engages in chemical reactions. What's a coactive nonmetal then? Maybe there is an answer, but I would like to hear it if we were still discussing that term. It would help a lot.

Now as for the new term, I find it rather strange to have a pre-halogen category that has six member whereas the halogen category has only four. I am also somewhat uneasy about having to intersect the terms "halogen" and "nonmetal." While you mentioned a 1885 source doing that, that was plain tautology back then when astatine wasn't known---I rather doubt it was meant to be a term. Regardless, neither of these concerns is a dealbreaker; we could live with that. I'd prefer we didn't for the reasons I have just outlined, but that is a mere personal preference and I don't feel very strongly about the whole issue of categorization as long as we have names that do not immediately call for an objection.

By the way, I don't recall supporting a binary division. However, there's a great number of things I don't recall, so this remark is not a claim of the opposite. I may have written something along the lines of "we could have it in principle and that wouldn't be too bad." I thought you had quoted me saying that here and that quote could maybe rule out this possibility, but I can't find that quote.--R8R (talk) 09:20, 22 August 2020 (UTC)

@R8R: I agree with you about a descriptive phrase, as far as this is preferable to a “neologism”.

As I see it, "coactive nonmetals are noted for their catalytic, catenative and covalent associations" (or something like that). Although it is a moot question, how does that seem?

Pre-halogen nonmetals are precisely that, no more, no less. I cannot do anything about the fact that they are positioned before the halogens, and that there are four halogen nonmetals (or six halogens, from F to Ts, if you prefer) and seven pre-halogen nonmetals.

Intersecting halogen and nonmetal: In an Introduction to chemical principles, Fernandez & Whitaker (1975, p. 197) wrote:

"It was seen that the noble gases form a logical "buffer" zone of relatively unreactive elements separating the very reactive alkali metals and the very reactive halogen nonmetals."

In our Block (periodic table) article we say:

"Metals of the s-block form ionic compounds with the halogen nonmetals in group 17."

Here’s a 2020 example using the term halogen nonmetal:

"Most semiconductor NCs are composed by (n −1)d10 metals of groups 11−15 (with empty or filled ns orbitals, such as Cu, Ag, Zn, Cd, In, Pb, and Bi, among others) and chalcogen, pnictogen, or halogen nonmetal atoms…" doi:10.1021/acs.accounts.0c00204.

The fact that the halogens have a well-recognised name and that the “other nonmetals” don’t is presumably a reflection of the seeming diversity of the latter e.g. lightweight hydrogen; fecund carbon; noble nitrogen; powerhouse oxygen; smelly sulfur; pyrophoric phosphorous; and mysterious selenium. Even so, at least their connection with organic processes is reasonably well known, I would’ve thought.

You stated your support for two categories of reactive nonmetals in archive 30, Dec 2017:

"While I am eager to be proven wrong, I continue to think that there is no good divide at all. I see myself agreeing on a divide with two clear self-descriptive relevant terms, but throughout all of this time, we haven't found a single one."

As you opined, the only thing holding things up was a name better than "other nonmetal", which we where unable to do at that time and for the preceding how every many years before that. Sandbh (talk) 13:16, 22 August 2020 (UTC)

Over to you, товарищ. --- Sandbh (talk) 13:16, 22 August 2020 (UTC)

Concise definition

Coactive nonmetals: Coactive ("acting together") refers to their behaviours in organocatalysis; linked geobiochemical cycles; tendency to form covalent or polymeric compounds; catenative proclivities (ring and chain forming); and dualistic Jekyll (biogenic) and Hyde (explosive and combustive) properties and applications.

Other nonmetals

A comment on the term "coactive nonmetals". I have never seen the word “coactive” before today in any context, so I am naturally worried about whether its use should be disallowed as “original research” which is not supposed to be on Wikipedia.

Sandbh has found some examples of chemical uses of the word “coactive” without the noun nonmetals. However, the word seems to be used in specialized contexts such as catalysis, and not in the sense proposed here of a general descriptor for certain columns of the periodic table.

In general, I think Wikipedia is supposed to indicate the vocabulary used in most other sources, which here means chemistry textbooks and chemistry journals. And it seems to me (without really checking the sources myself I admit) that the usual term is just “other nonmetals”, as in “halogens, noble gases and other nonmetals”. So why do we need to replace this phrase? Dirac66 (talk) 18:29, 10 August 2020 (UTC)

@Dirac66: Thank you.

Yes, you're right, the most popular form is other nonmetals, in the absence of anything more meaningful. Lesser known names for the nonmetals occurring in this part of the table are:

• biogen nonmetals;
• CHONPS nonmetals;
• intermediate nonmetals;
• light nonmetals;†
• organogen nonmetals;
• orphan nonmetals;‡ and
• quintessential nonmetals.

† e.g. Williams RJP 1981, The Bakerian Lecture, 1981 Natural selection of the chemical elements, Proc. R. Soc. Lond. B 1981 213, 361-397 (365)

‡ In a juvenile-level book called, Science of everyday things: Real-life chemistry (Knight 2002, Gale Group), which divides the nonmetals into noble gases, halogens, and "orphan" nonmetals. I laughed when I saw it. In a funny way, if only it wasn't so tragic, it is marginally better than other nonmetals.

Previous discussions in our project have centred on the meaningless nature of the "other nonmetals" label.

It's puzzling that, in the literature, the metals start out loud and proud, as alkali metals; alkaline earth metals; Ln/An; transition metals; and then fade away with the sixteen different names for the post transition metals. Then there are the reasonably well established metalloids, even though their boundary can move around a bit. And then we come to the first of the really well recognised nonmetals in a train wreck of classification science. They may as well be called the schemozzle nonmetals. After them, as you observed, follow the well-known halogen nonmetals; and the noble gases.

On why we need to replace the phrase "other nonmetals", I feel the answer is because it is unhelpful; poor classification science; does a disservice to chemistry in this part of the periodic table; and a better solution is available. The situation is as like standing back and saying a good job wad done with categorising most of the periodic table, with the exception of the leftover, other, or remanent nonmetals. The result is what Zuckerman and FC Nachod (1977, preface) said i.e. “The marvellous variety and infinite subtlety of the non-metallic elements, their compounds, structures and reactions, is not sufficiently acknowledged in the current teaching of chemistry” in Steudel's Chemistry of the nonmetals.

I do not see any OR. All the properties involved, including the recognition of H, C-O, P-S, Se forming a category are in the literature. Maybe there is smidgeon of WP:BOLD. I guess a chemist who saw "coactive nonmetals" might wonder what they are if they weren't familiar with the "coactive" adjective. They might look up coactive in a dictionary to see what the term means, or they might look at the nonmetal article, and see we are referring to the other nonmetals. At which point they might say, ah the term is unfamiliar, but the category, as other nonmetals, is. Now I get it. Much better than "other" which tells me nothing.

Could you please also see my response to R8R, above. Sandbh (talk) 07:47, 11 August 2020 (UTC)

@Dirac66: It seems like a completely generic term for the other nonmetals H, C, N, O, S, P, Se would be pre-halogen nonmetal as that is what they are, no less no more. Your thoughts? thank you, Sandbh (talk) 06:41, 21 August 2020 (UTC)

Biogeochemical cycles

I'm a bit gobsmacked to learn that we have articles on the following biogeochemical cycles:

1. Hydrogen cycle; 2. Carbon cycle; 3. Nitrogen cycle; 4. Oxygen cycle; 5. Phosphorus cycle; 6. Sulfur cycle; 7. Selenium cycle

I'd never heard of 1, 5 and 7, the last one especially. Who'd've thought?

Wow! --- Sandbh (talk) 08:05, 18 August 2020 (UTC)

Past, present, future(?) categories

Looking ahead

Here's what I have in mind:

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Lanthanoid	Transition metal	Post-trans- ition metal		Coactive nonmetal	Halogen nonmetal	Noble gas
		Actinoid

Aesthetically, Ln over An is more pleasing. --- Sandbh (talk) 07:13, 16 August 2020 (UTC)

re the aesthetical note: I don't think this is an aesthetic freedom. If the bottom row has these two stacked, this expression should have a meaning, since it introduces a new distinction. -DePiep (talk) 19:21, 9 September 2020 (UTC)

Where we've been; where we could be

In graphical form, loud and proud:

— Colour category history 2002−2020—
 

2002	Rationale given at the time	ca. 2003−2013	2013−2018	2018	Proposed	Result
Alkali metal	very reactive and therefore dangerous = red	same	same	same	no change	Alkali metal
Alkaline earth metal	nice earthy colour = easy to remember					Alkaline earth metal
Lanthanoid	chosen arbitrarily					Lanthanoid
Actinoid						Actinoid
Transition metal						Transition metal
Metal	true metals are closest in colour to grey	Other metal/Poor metal	Post-transition metal			Post-transition metal
Semimetal	intermediate colour between above and below	Metalloid	same			Metalloid
Nonmetal	elements most essential to life; most life on Earth measured by biomass is photosynthetic, and chlorophyll is green	Other nonmetal	Polyatomic nonmetal (C, P−S, Se)	Reactive nonmetal	Coactive nonmetal	Coactive nonmetal
Halogen	fluorine gas is yellowish as are many precipitates of halogens	Halogen (inc. At)	Diatomic nonmetal (H, N, O, F−I)		Halogen nonmetal	Halogen nonmetal
Noble gas	non-reactive for practical purposes; light-blue is soft and soothing; aka aerogens = blue sky (Sandbh contribution)	same	same	same	no change	Noble gas

---

Sandbh (talk) 07:13, 16 August 2020 (UTC)

The colors are (better: should be; see the original AM motivation for red) independent of the category content, and independent of cultural meaning. And we should strive to enhance that. That said, some improvements are needed, e.g. in color contrast, improving re colorblindness, and differentiation say recognisable between Table <--> legend, clear between-category border-difference. For clarification of current ideas indeed one can use current colors reassigned. Number of proposed categories should not be determined by color(-limitations, -goals). If the PT should have 14 categories, I think coloring them is the least problem.

IOW: go ahead with the proposal development, don't be bothered by colors. DePiep (talk) 18:43, 9 September 2020 (UTC)

Observations

• There are no WP:NEO or WP:OR violations, per the chat R8R and I are having.
• @YBG: On 7±2, there is a little less to this than meets the eye. From the proposed legend in the Looking ahead subsection it is rather 3 (5-1-3) as in metal-metalloid-nonmetal, and within those three bundles chunks, {AM, AEM, La/An, TM, and PTM}, {Metalloids}, and {CN, HN, and NG}. 7±2 is thereby observed, similar to the rooms in a house memorisation technique. This is better taxonomically and mnemonically.
• The YBG rules are met.
• The green of the other nonmetal-coactive nonmetal category is very appropriate. For that matter, I like the yellow of the halogen nonmetals, and the blue of the noble gases (it looks turquoise on my monitor).
• The other nonmetal category exists in the literature. All the properties of interest are set out in the literature. No new ground in chemistry will be broken. The meaning of coactive is supported by reliable sources. The subject matter is notable.

--- Sandbh (talk) 07:13, 16 August 2020 (UTC)

Scheme royale

Legend 1: Periodic table categories

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Lanthanoid	Transition metal	Post-transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
		Actinoid	Noble metal ✣

This will address any residual concerns to do with "coactive nonmetals".

I've added an optional "noble metal ✣" sub-category of transition metal. The alchemical looking four balloon-spoked asterisk is to distinguish the noble metals in our main periodic table, thus e.g. Pt ✣, Au ✣. The actual positioning of the asterisk within a noble metal's PT box is flexible, having regard to coding and design considerations.

In our info boxes a noble metal would be categorised as Transition (noble) metal.

Figure 1: The eightfold way (category counterpart map)

	Noble gas
Active metal   Alkali metal   Alkaline earth metal   Lanthanide   Actinide	←↑↓→	Halogen nonmetal
Transition metal		Pre-halogen nonmetal
Post-transition metal		Metalloid
	Noble metal

Table 1: Alt-category names

Active metals	Hyper metals
Transition metals	Working metals
Post-transition metals	Poor metals
Noble metals	High society metals
Metalloids	Junior nonmetals
Pre-halogen nonmetals	Respectable nonmetals
Halogen nonmetals	Psycho nonmetals
Noble gases	Cup of tea nonmetals

The symmetrical relationships seen in Fig 1. can facilitate learning since fewer observations are required to describe the applicable system. Further, concepts that possess symmetry can be more easily grasped than those that do not.

Students or instructors who enjoy more visceral distinctions may enjoy category names with attitude, as shown in Table 1. --- Sandbh (talk) 01:32, 17 August 2020 (UTC)

Comments by YBG

1. Number of categories: 7±2. It is not 5+1+3 as Sandbh suggests, but more closely akin to 6+1+3 because you are using two colors for the inner transition elements. And, I would submit, because we have a unified periodic table with a unified color scheme (rather than three separate tables, metals, metalloids, and nonmetals), what you are proposing is not even 6+1+3 but rather a simple 10.
2. Categorization (a): Leftover category. Your idea to use *​coactive nonmetals eliminates the leftover nature of the category name but it does not change the fact that the leftover nature of the category itself. I strongly suspect that in the treatment of nonmetals, this category is universally treated as the last nonmetal category to be treated. This strongly suggests that whatever in-category similarities and between-group dissimilarities exist, the primary distinguishing feature is that these are NNNHNM - Non-noble, non-halogen nonmetals. Trying to find a synonym for the NNNHNM does not change the fact that this category is a hat-trick of left-over-ness.
3. Categorication (b): Good taxonomy. (or do the halogens need to be both a group and a category). It seems to me that much of the argument for dividing the reactive nonmetals here at WP:ELEM and in the literature is the desire to talk first about the halogens and then talk about the rest. I strongly believe that only the noble gases deserve to be a monotypic category. Otherwise, why stop there? Why not have chalcogen nonmetals, pnictogen nonmetals, carbon group nonmetals, and the comparable metalloid and metal categories?
4. Nomenclature (a): Coactive. This is a term that is never used non-technically, and, if I understand correctly, only rarely in a technical context, and that with a completely different meaning. For this to be even considered, the following analogy would need to be true:

   coactive metal : metal :: *​coactive nonmetal : nonmetal

   I'm willing to be corrected, but by my understanding of the information presented, this analogy does not hold. I note that this analogy is IMO a necessary but not sufficient condition for using the term.

5. Nomenclature (b) Good naming. The best names are those that are commonly used and meaningful in both technical and non-technical contexts, but at a minimum they should be commonly used in one or the other. "*​Coactive nonmetal" fails on both counts; the adjective "coactive" is only vaguely familiar and that only in a specialized technical context. Contrast this with the other category names (pun intended).

Category	To the professional	To your non-technical neighbor
Alkali metal	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Alkaline earth	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Lanthanoid	Term commonly used	Term totally meaningless
Actinoid	Term commonly used	Term totally meaningless
Transition metal	Term commonly used	Adjective understandable, meaning identical (but begs question, "between what and what?
Post transition metal	Understandable but not commonly used	Adjective understandable, meaning identical (but begs question "after what transition?")
Metalloid	Term commonly used	Term totally meaningless
Reactive nonmetal	Understandable but not commonly used	Adjective understandable, technical & non-technical meanings identical
Noble gas	Term commonly used	Adjective vaguely familiar, but with slight difference in meaning
Other nonmetal	Term commonly used (but has no meaning)	Term completely understandable, technical & non-technical meanings identical
Coactive nonmetal	Term not commonly used, never in this context	Term completely meaningless

(If there is any disagreement on the correct values in this table, please let me know and I will correct them)

Even the much-maligned "other nonmetal" comes out better than "*​coactive nonmetal" in this regard. It is frequently used in the literature, and its meaning (such as it is) is clear to both technical and non-technical audiences, but as WP:ELEM previously agreed, it is absolutely non-descriptive from both a technical and non-technical perspective.

I am quite content with the status quo, which was attained after at least two voluminous mega-discussions. I am certainly not convinced that a change is warranted, but if it is, I think it should be in the following direction:

Reactive metals Alkali metals Alkaline earth metals

Inner transition elements Lanthanides Actinides

Transition metals

Post-transition metals

Metalloids

Reactive nonmetals

Noble gasses

I am not agitating for this change, merely stating that I am far more comfortable with a change in this direction than in the direction proposed by Sandbh. YBG (talk) 02:15, 17 August 2020 (UTC)

Sandbh response 1&2

@YBG: Thank you. I'll respond shortly. In the meantime, since I expect I will abandon coactive nonmetal in favour of pre-halogen nonmetal could you please let me know how you feel about the SR proposal? We're close in our thinking. I believe I do like the (re)active metals and the inner transition metals. Sandbh (talk) 02:42, 17 August 2020 (UTC)

That eliminates my reason #4 and changes reason #5. As a category name, I'd rate pre-halogen as slightly worse than post-transition. One question, is this term ever used in the literature? How does its frequency compare to post-transition metal or reactive nonmetal, the two category names we have that aren't frequently used?

And of course, this name change does nothing to my reasons 1, 2, and 3. YBG (talk) 03:19, 17 August 2020 (UTC)

@YBG: I've addressed your reasons 1, 2 and 3 below.

Yes, the term pre-halogen is a real word. The main references are to the pre-halogen era of lighting (you'll find this expression in our Headlamp article); and I saw a reference or two to pre-halogen sedimentation, in a geological sense. I presume this is a reference to non-saline deposits.

It’s good to see ^_^ that in the pre-halogen era, lighting was provided via a pre-halogen nonmetal, carbon ^_^ So that gives us a pre-halogen era pre-halogen nonmetal = PHEPHM ^_^ Sandbh (talk) 09:07, 17 August 2020 (UTC)

Its frequency compared to post-transition metal or reactive nonmetal is insignificant. I feel this is not a significant concern. "Halogen" is widely recognised (by chemists), as is the plain English prefix "pre-" (prehistoric; a pre-nuptial; pre-natal classes; pre-school/care). Pre-halogen nonmetal is more informative than "other nonmetal". Given the hoi poloi of category names for nonmetals in this part of the periodic table, we have discretion on how to proceed, as provided for by WP:MOSWTW.

I feel that "reactive nonmetals" obscures information that is already in the literature about the discrete shared properties of nonmetals in this part of the periodic table e.g. the halogen nonmetals' uniformly high IE, EA and EN values, unlike the pre-halogen nonmetals. In the context of a better encyclopaedia, merging the two categories of NNNM represented a retrograde step. I signed up to it at the time out of dissatisfaction with the "other nonmetals" category. That said, we did not know then what we know now.

We will now lose nothing by splitting the reactive nonmetals. We will rather gain a much superior treatment and appreciation of the nature of the nonmetals involved. Nothing else changes. That is why I'm advocating for change.

Please let me know if you have any outstanding concerns.

--- 08:17, 17 August 2020 (UTC)

1. I feel we could agree(?) the categories look like this…

1	1	1
6	1	3

…where the top row is metal | metalloid | nonmetal. By chunking, the 7±2 rule is satisfied.

2. Yes, I agree it is a leftover category name (rather than a leftover category of nonmetals). That said, all the shared characteristics are set out in the literature. Yes, I agree they are NNNHNM, hence the proposed category name pre-halogen nonmetal which is exactly what they are.

3. We don't use those group category names as there would be too many categories. As well, our categories are designed to show the L-R transition in metallic to nonmetallic character.

4.–5. No comment as I'm moving away from this term.

This is what you have now:

	Noble gases
Reactive metals Alkali metals Alkaline earth metals	←↑↓→	Reactive nonmetals F-I
Inner transition elements Lanthanides Actinides
Transition metals		H, C-O, P-S, Se
Post-transition metals		Metalloids
	Noble (transition) metals

The Ln and An are "reactive" too. Their standard electrode potentials range from about −1.8 to −2.8; the group 1–2 metals run from about −1.8 to −3.0. The "reactive" sense you are referring to is better captured by "active" metals.

I support a merge of the AM and AEN. I ask for your support for splitting the reactive metals, which is good classification science, and has been the predominant presentation in our PT. We only merged the NHNNNM out of dissatisfaction with the other nonmetal category name.

I see you have since replied, so I'll have a look at that next. --- Sandbh (talk) 07:03, 17 August 2020 (UTC)

YBG reply

My comments:

• re 1. Number of categories. We want to color the entire periodic table with a single color scheme. This in and of itself means that we should strive to have the unchunked number of categories close to the ideal seven. But even more than this, I submit that we actually do not chunk these categories, Do we actually chunk these categories? Or do we generally discuss them all together? In what context(s) do we discuss the categories? Most frequently, the context is discussing all of the categories together. Slightly less frequently, we discuss a single category in and of itself. We almost never discuss the metal categories (or the nonmetal ones) by themselves apart from discussing all of the categories, metal, metalloid, and nonmetal alike. From this I conclude that we do not actually chunk these categories into three mega-categories but treat them together.
• re 2. Left-over-ness. I think you have missed my point here. My main point is that the category itself is a leftover category. I used the left-over-ness of the category name as evidence of the left-over-ness of the category itself. When WP used the leftover name "other nonmetal", we were showing that we considered the category itself to be a leftover category. If we adopt the non-leftover name "pre-halogen nonmetal", we are showing that we consider the category to be a non-leftover category. But what does the literature show? The overwhelming use of the leftover name "other nonmetal" testifies that the literature overwhelmingly treats the category as an "(e)-none-of-the-above" leftover category. Having WP change the name we use would not change the testimony of the literature as to the nature of the category. At issue here is how much within-group similarity there actually is.
• re 3. Taxonomy aka classification science. Again, my post failed to get the point across, causing you to focus on a relatively minor point. My main point here in whatever context we are, if we want to discuss the halogens, we do not need a halogen category to support this discussion, as we already have a halogen group. The term "Reactive nonmetals" does not obscure halogen info in the literature any more than "transition metal" obscures information about the iron group or the coinage metals.
• re 4. & 5. Now moot
• re 6. Distractions. (a) AM+AEM. I’ll happily reject the (re) prefix; "active metal" seems better than "reactive metal". But I prefer to treat AM+AEM as a separate issue rather than engaging in logrolling. (b) And by the way, I don't find your circular presentation that includes noble metals to be very helpful in this discussion. The chart is interesting and would be improved with the PTM on the right side, but IMHO it is a distraction in this discussion.

YBG (talk) 20:05, 18 August 2020 (UTC)

@YBG: 1. Number of categories. I suggest it isn't a matter of how we do or do not chunk or do or do not discuss the categories together. Rather it is a question of catering for the common reader of our encyclopedia, drawing on the literature. That is why, in my opinion, our legend is constructed the way it is, with the three major categories along the top, broken down into metal, metalloid, and nonmetal (sub)categories. That is consistent with the way chemistry is taught, with its top level focus on metals and nonmetals or metals, metalloids, and nonmetals. From there each of these major divisions are further explored, consistent with the application of chunking in learning theory (I speak here with benefit of an academic background in learning and development). I support you with your request for a merge of the AE and AEM. I have no strong concern about a separate category for the noble metals, even though it looks nice. That will leave us with eight categories, four metallic and four nonmetallic:

Re(active) metal
Inner transition metal
Transition metal
Post-transition metal
Metalloid
Pre-halogen nonmetal
Halogen nonmetal
Noble gas

A 4+4 arrangement is pleasing.

2. Left-over-ness. I follow you. This is a good example of the limitations of post-by-post chat.

The situation is analogous to the post-transition metal category and its 16 alternative category names, including other metals.

The existence of the metals involved is not in question. All the properties involved are set out in the literature.

The nonmetals involved have 10 or so alternative category names. If I may clarify something you said, the literature does not "overwhelmingly" use the expression other nonmetals. Rather, this seems to be the most common term of the alternatives, similar to the leading horse in a horse race, with a couple of other contenders not out of reach. If we are true to the literature we should in fact have an other nonmetals category! From a bad field I feel a generic category name in the form of pre-halogen nonmetals is preferable and acceptable. I did contemplate calling them the geobiochemical nonmetals. ^_^

The existence of H, C-O, P-S, Se as a category is not in question. All the characteristic properties involved are set out in the literature.

I've set out their remarkable within-group properties before. The pre-halogen nonmetals feature a remarkably rich array of shared characteristics. Summarising, they are distinguished by their:

1. moderate non-metallic character (IE, EA, EN)
2. covalent or polymeric compounds;
3. prominent (and linked) biogeochemical roles, each having individual "cycle" articles—unlike the other ^_^ nonmetals
4. proclivity to catenate (form chains or rings);
5. multiple vertical, horizontal and diagonal relationships;
6. uses in, or as, combustion and explosives;
7. uses in organocatalysis; and
8. dualistic Jekyll (#2) and Hyde (#5) behaviours.

Poster from the 1880s: Jekyll transforms into Hyde by imbibing a cocktail of chemicals prepared in his laboratory. It is a curious contrast that the same coactive nonmetals that play a crucial characteristic capacity in biogeochemical cycles have changeable customary callings in combustible and concussive chemical concoctions. On the one hand they sustain life; on the other they let us play with fire.

3. Taxonomy aka classification science. The halogens may be discussed in two ways. First as group 17. Second as the four nonmetals (F−I) and one metal (At). Please bear in mind our periodic table is not a groupic table. It is a metallicity table. That said, we include the group names along the top, in order to provide a flexible approach. The halogen category by itself, obscures the nature of astatine as a post-transition metal. That is not an issue for the transition metals: they are all transition metals. Merging the halogen nonmetals and pre-halogen nonmetals hides the nature of the pre-halogen nonmetals.

6. Distractions. (a) That is good. Yes, I'll support a combined AE and AEM category as a separate issue. (b) I feel the circular presentation is helpful since it's something we can't do so well now. I say this as the pattern involved facilitates teaching and learning the periodic table; fewer observations are required to describe the applicable system; and concepts that possess symmetry can be more easily grasped than those that do not (Randall L.: Warped passages: Unravelling the universe's hidden dimensions. Penguin Books, London, p. 193 (2006)).

Looking forward to your further consideration of these interesting matters. Sandbh (talk) 03:53, 19 August 2020 (UTC)

I recognize that it is a minor point, but I take issue with your statement that our enwiki PT is not "groupic". It would be fair to say that PTs discussed in § Periodic ziggurat of the elements and § A partially disordered periodic table are "non-groupic", but not "our" PT. Yes, our color scheme is not "groupic", but any PT that displays each group in a column by itself could be considered "groupic". But perhaps I misunderstand what you mean. And as I say, I recognize that this is quite a minor point, and not I believe relevant to the main point here, which is our disagreement about the wisdom of isolating the halogens from the remainder of the nonmetals. YBG (talk) 05:40, 1 September 2020 (UTC)

Septenary heterogenous pre-halogen compounds

The pre-halogen nonmetals are capable of forming these. A simpler example is C₂₀H₂₆N₄O₁₀PSSe. I was surprised to learn that the chemical composition of the VX nerve agent is C₁₁H₂₆NO₂PS.

The first discovered nerve agent was tabun or GA, of composition C₅H₁₁N₂O₂P. Among the V series successors, VX is the most studied: C₁₁H₂₆NO₂PS. The selenium analogue of the VE nerve agent is selenophos C₁₀H₂₄NO₂PSe. This is more potent than VX =:ox

On the one hand the PHN sustain life; on the other they let us play with fire.

--- Sandbh (talk) 07:15, 23 August 2020 (UTC)

Twelve categories

By Dalby (2020) here:

s block • AM • AEM

f block • REE (Ln) ± • An

d block • TM (REE): Sc, Y • TM • TM (precious metals)^

p block • Post-transition metals • Metalloids • Polyatomic nonmetals • Diatomic nonmetals • Noble gases

^± La-Lu

^ rhenium, PGM, coinage metals, and mercury

@YBG, R8R, and DePiep: Twelve categories seems like a lot. That said, the author has provided two ways to chunk things down: by block or by metal-metalloid-nonmetal. So that's OK.

The way they have flagged the REE is interesting, given RE/REE/REM is nearly three times more popular terminology than lanthanides.

The precious metals category does not have so much relevance, being a little too diverse as such. Still, it does show the TM can be chunked down into more manageable parts:

Legend 2: Periodic table categories

Metal					Metalloid	Nonmetal
Alkali metal	Alkaline earth metal	Rare earth metal	Transition metal (ρ, ✣)	Post-transition metal		Pre-halogen nonmetal	Halogen nonmetal	Noble gas
		Actinoid

ρ Transition (rare earth) metal: Sc, Y, La

✣ Transition (noble) metal: Ru-Pd, Os-Pt, Au

Yes, I am proposing we replace the Ln category with the REM category, including showing Sc-Y-La as transition (rare earth) metals. --- Sandbh (talk) 00:16, 20 September 2020 (UTC)

@Sandbh: I think that the idea has its merit but Wikipedia is not the right place for such a proposal.

We use non-overlapping categories. The major advantage of that is that it's easy this way to distinguish groups and the scheme doesn't look too difficult to understand. If our major scheme will have first and secondary category notation, it will be more complicated, and that's a very big disadvantage. This will work poorly with a big table unless a person specifically thinks they'd love to gaze at the PT and it will probably be even worse with our small tables like the one in the infobox. Another disadvantage is loss of the lanthanide-actinide parallel (leading to the obvious question why it is not there because everyone who knows about the actinides knows equally well about the lanthanides). The advantage is not clear for me: it's safe to say everybody who understand "rare earth metal" understands "lanthanide" and doesn't find it any less intelligible, and vice versa.

I would not say that Dalby's proposal helps manage the big category of transition metals. Rather, it helps establish that some transition metals are special and deserve a subcategory and effectively discard the rest of them as less important. That's hardly what I'd want to show in a general-audience PT. I think that there in principle could be a talk of subcategories within categories if we can divide an entire category into subcategories, provided subcategories would be clearly secondary and not displayed in small tables. More than a half of elements in the TM group, however, remains outside of all subgroups, which really puts more spotlight on platinum at the expense of titanium, which I find undesirable.

It appears there is no appetite to say that Sc and Y are rare earth metals and not transition metals, and I find myself glad about that.

To sum it up, I think the proposal will result in a less user-firendly table and put us in more jeopardy because of the category overlap, which is why I suggest we don't implement it.--R8R (talk) 10:58, 20 September 2020 (UTC)

I fully agree with the well-formulated comment R8R made here.

I add: actually, this would be three levels of categorisation, not two, since we already show metal-metalloid-nonmetal as supercategorisation. Also, I do not see an improvement by introducing Venn-like divisions (like re-using halogen in here). Essence of this (enwiki) categorisation is that it shows categories independent of groups and periods (orthogonality). The fact that some nonmetals are a halogen already is noted by the group name 'halogens'; "halogen nonmetals" readily can be deducted from the PT. That two (only two) categories correspond with groups is incidental. OTOH, other categories, like major catgegory metalloids, actually add new info to the PT. -DePiep (talk) 15:49, 20 September 2020 (UTC)

Proposed name for group 3

I hereby recommend that the IUPAC adopt a trivial name for the scandium group: the disputogens. You heard it here first. YBG (talk) 22:36, 1 August 2020 (UTC)

No, that would be too easy. It should be called the "disputogens" only when it means Sc-Y-Lu-Lr. When it means Sc-Y-La-Ac, it should be called the "arguenogens". Perhaps another name should be given to them when all 30 lanthanides and actinides are included (Sc-Y-*-**), such as the "grawlixogens".

(removes tongue from cheek). Double sharp (talk) 04:09, 2 August 2020 (UTC)

So much for the work of IUPAC's Group 3 project then. Sandbh (talk) 04:33, 2 August 2020 (UTC)

@Sandbh: I'm quite confident the IUPAC will have no problem separating tongue from cheek as Double sharp and I do. YBG (talk) 05:22, 23 September 2020 (UTC)

@YBG: I thought it was a disrespectful comment that showed no appreciation of the background to the dispute as well as contributing nothing to the discussion. Sandbh (talk) 06:59, 23 September 2020 (UTC)

Steudel's chemistry of the non-metals

Steudel R 2020, Chemistry of the Non-Metals: Syntheses - Structures - Bonding - Applications, De Gruyter,

This newest international edition is an updated translation of the latest German edition of 2013. I think the last English edition appeared in 1977. Sandbh (talk) 05:52, 2 August 2020 (UTC)

Why do none of the transition metal groups have standardized names?

To give all eighteen groups a common name, may I propose the addition of ten more names?

1: the alkali metals (when excluding hydrogen), 2: the alkaline earth metals, 3: the disputogens, 4: the titanogens, 5: the vanadogens, 6: the chromogens, 7: the manganogens, 8: the ferrogens, 9: the cobaltogens, 10: the nickelogens, 11: the coinage metals, 12: the volatile metals, 13: the icosagens/the trigens, 14: the crystallogens/the tetragens, 15: the pnictogens, 16: the chalcogens, 17: the halogens, 18: the noble gases

We can also extend this to the f block - the lanthanogens, the cerogens, the praseodymogens, the neodymogens, the promethogens, etc.

I know this is WP:OR, but we need better names instead of trying to remember whether nickel is in group 8, group 9, or group 10. ― Дрейгорич / Dreigorich Talk 10:08, 4 August 2020 (UTC)

@Дрейгорич: They do have standardised names, sort of, in that the IUPAC Red Book provides for them to be called according to the first element in each group, so group 3 is the scandium group.

I’ve seen references to: early transition metals (groups 4 to 7); ferrous metals (Fe, Co, Ni); and of course the platinum group metals.

And there is Group 5 as the acid earth metals. The name is a reference to the acidic nature of the pentoxides of this group. See: Remy H 1956, Treatise on inorganic chemistry, vol. 2, Elsevier, Amsterdam, p. 87

--- Sandbh (talk) 11:41, 4 August 2020 (UTC)

The acid earth metals. Huh. Well, I know what I'm naming our rock band. ― Дрейгорич / Dreigorich Talk 11:47, 4 August 2020 (UTC)

@Дрейгорич: You'll be in good company. There was a band called Rare Earth in the 1970s. I see they're still active. Sandbh (talk) 00:35, 7 August 2020 (UTC)

Pentoxides of V, Nb, and Ta should better be called amphoteric. Pentoxides with weak enough basic character to be safely called acidic rather occur from group 6 onwards. Double sharp (talk) 13:07, 4 August 2020 (UTC)

Not really; it depends on the context.

Remy writes:

"Fifth sub-group of the periodic system: The acid earths

Although definitely metallic in character in the elementary state, they are decidedly acidic in their normal oxides, the pentoxides. This is true of V, Nb, and Ta at least—and for this reason their pentoxides are also known as the acid earths (i.e., acid-forming metal oxides), or as the earth acids…it appears…the basic character is more strongly developed in Pa than in the first three members of the group, which are not capable of forming simple salts in aqueous solution even with the strongest acids."

Lidin (1996), writing in "Inorganic substances handbook," refers to V₂O₅ as amphoteric with predominating acid properties, and Nb₂O₅ as an acidic oxide. Our article on the latter notes it dissolves in fused alkali. Sanderson (1967), writing in "Inorganic chemistry", rates Ta₂O₅ as amphoteric, favouring acidity.

We can see then that Remy was referring to which side of the basic-acidic line the oxides fell on.

In contrast, Group 4 is a mixed bag: TiO₂ is amphoteric, favouring acidity; and ZrO₂ and HfO₂ are amphoteric, favouring basicity.

I haven't heard of pentoxides of Group 6. From Greenwood & Earnshaw these seem to be intermediate compounds having formulae such as Mo₄O₁₁, Mo₁₇O₄₇, W₁₈O₄₉ and W₂₀O₅₈ (p. 1008). Turning now to the normal oxides of Group 6, MoO₃ is "distinctly amphoteric" (Wiberg 2001, p. 1388) and dissolves in strong acids to form salts which contain the bent molybdanic ion MoO₂²⁺ in hydrated form: [MoO₂(H₂O)₄]²⁺.

Thus, Group 5 is the first group in which the normal oxides favour acidity, hence the term acid earths. --- Sandbh (talk) 01:22, 5 August 2020 (UTC)

Greenwood and Earnshaw (2nd ed., p. 981): "V₂O₅ is amphoteric. It is slightly soluble in water, giving a pale yellow, acidic solution. It dissolves in acids producing salts of the pale-yellow dioxovanadium(V) ion, [VO₂]⁺, and in alkalis producing colourless solutions which, at high pH, contain the orthovanadate ion, VO₄³⁻."

Greenwood and Earnshaw (2nd ed., p. 982): "Niobium and tantalum also form various oxide phases but they are not so extensive or well characterized as those of vanadium. Their pentoxides are relatively much more stable and difficult to reduce. As they are attacked by conc HF and will dissolved in fused alkali, they may perhaps be described as amphoteric, but inertness is the more obvious characteristic."

Indeed, true that there are no stoichiometric M₂O₅ for group 6, but we can already see acidic properties dominate more from all that polyanion chemistry famous for Mo and W. Greenwood and Earnshaw call +6 oxides of Cr, Mo, and W acidic (p. 1007).

Of course bounds of amphotericity depend on context. There is simply a continuum from more to less acidic properties, different authors may consider a different range of what is sufficient to call an oxide amphoteric. That's why you have to pick one source's classification for consistency. Otherwise the classification is taken out of context. Nb₂O₅ can't possibly be more acidic than MoO₃ with the lower cationic charge by standard general chemistry. Double sharp (talk) 02:37, 5 August 2020 (UTC)

Some more observations:

• Issa IM and Khalifa H 1954, The amphoteric properties of molybdenum trioxide and its isoelectric point. J. Indian. Chem. Soc. 31, 2. pp. 91-96
• Sisler HH et al. 1959, General chemistry: A systematic approach, Macmillan: "Tungsten trioxide, like its molybdenum analog, is amphoteric, with acidic properties predominating." p. 705
• Songina OA 1970, Rare metals, 3rd ed., Israel Program for Scientific Translations; [available from the U.S. Department of Commerce, Clearinghouse for Federal Scientific and Technical Information, Springfield, Va.: "converted to the anhydride MoO₃ at 115 - 130°C. Both the anhydride and the acid are somewhat amphoteric and readily dissolve in solutions of alkalis." (p. 35).

[Above is an unsigned contribution by Sandbh. Double sharp (talk) 09:17, 5 August 2020 (UTC)]

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Yes, no doubt you can find lots of reliable sources calling MoO₃ amphoteric. But can you find any doing so that also calls Nb₂O₅ acidic like you do when you bring together the different bounds of amphotericity used by Remy and Wiberg? Double sharp (talk) 09:16, 5 August 2020 (UTC)

The rest of the names

Background

Transition metal group names 3 4 5 6 7 8 9 10 11 12 Scandium group metals Iodide metals1 Acid earth metals Yellow earth metals2 Heptoxide metals3 Red metals4 Weather metals5 Catalytic metals6 Coinage metals Volatile metals Sc Y La Ti Zr Hr V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg If we can fill out the blanks I'll see I can get the names published in a journal article. Sandbh (talk) 06:52, 5 August 2020 (UTC) Note 1: Refers to the iodide crystal bar process: "The only metals it has been used to purify on an industrial scale are titanium, zirconium and hafnium, and in fact is still in use today on a much smaller scale for special purity needs." Sandbh (talk) 13:36, 5 August 2020 (UTC) American school bus, painted in chrome yellow Note 2: The background is that chrome yellow (i.e. lead chromate) was also referred to as "orange earth". Lead chromate has an orange-yellow colour, so I can see where the reference to orange comes from. The other yellow earths are molybdenum trioxide; and canary yellow tungsten trioxide powder. Sandbh (talk) 00:19, 23 August 2020 (UTC) Note 3: “The same probably applies to the triads of elements, between the two halves of large periods; they constitute however the transition between these two halves, between the heptavalent metals of the first half of the large periods, whose highest oxides are acidic…”, here Sandbh (talk) 10:17, 5 August 2020 (UTC) Group 7 as the heptoxide metals refers to the observation that this is the first group with exclusively acidic oxides in their highest oxidation state. (The +6 oxides of group 6, while acidic, all show some amphoteric character.) This is the only group in which binary metal heptoxides are found; each such oxide has a unique crystal structure (Mast 2018, p. 5). Note 4: From the reddish-brown colour of rust; the most prevalent Ru precursor is ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO 4(OH)2− 2 formed upon reaction by OsO4 with a base. Sandbh (talk) 02:28, 7 August 2020 (UTC) Note 5: From the use of cobalt chloride as a humidity indicator in weather instruments ; rhodium plating used to "protect other more vulnerable metals against weather exposure as against concentrated acids or acids fumes" (Küpfer 1954, p. 294); and the "rainbow" etymology of iridium. Note 6: From G&E: "They are…readily obtained in finely divided forms which are catalytically very active." (p. 1148). Sandbh (talk) 07:02, 5 August 2020 (UTC) The new category names do not seem very effective to me. "Scandium metals" seems unnecessary when "scandium group" tells us exactly the same thing and is more standard. "Acid earth metals" for group 4 is in conflict with the citation you got for it where it means group 5 (and ZrO2 and HfO2 are rather on the basic side of amphotericity). "Aerospace metals" seems more relevant to Al than to V, Nb, and Ta. "Yellow metals" is a bit strange for Cr, Mo, and W as none of them are yellow, and Cr compounds are known for many other colours too. "Heptavalent metals" would literally include every metal that manages a +7 oxidation state. "Iron metals" will likely be confusing with the "iron triad". "Catalytic metals" would grab most of the transition metal series, not just Ni, Pd, and Pt. "Volatile metals" would literally include, say, Po. That is my opinion. You may disagree, and if so I will not give more comments on this since this is not WP-related. Double sharp (talk) 11:04, 5 August 2020 (UTC) @Double sharp: Good feedback. Thanks for noting my error about the acid earths; now corrected. Group 3 are now the scandium group metals; that is better. I've reverted 6 back to ? Group 7 as heptavalent metals refers to the fact[?] that this is the first group with exclusively acidic normal oxides. I take normal here to refer to the MOS. (Aiee! There’s a blast from the past ^_^) I don’t see the term "iron triad" as often as I hear "ferromagnetic metals", and I always forget their order. I’ve changed the name to iron group metals. "Volatile metals" is in the literature for group 12; Po is a chalcogen metal. There sure is a crash in MP after group 11, as cited in our post transition metal article. I know many TM have catalytic properties. That said, if you asked me about TM catalysts, Pd and Pt would be the first to come to mind. I haven't checked G&E as to why they highlighted group 10 for their very catalytic presence. So there are two groups to go: 6 and 9. Group 9 are the densest group of the TM. Obvious name is heavy metals but that would be confusing. Sandbh (talk) 13:22, 5 August 2020 (UTC) I don't think "normal" is a good characterisation of oxidation states like Cr(VI) and Mn(VII) that are well-known from high school as strong oxidants. Especially not when maximum oxidation states would include Ag(III), or, even more exotically, Ir(IX). But, since this is for outside Wikipedia, whether you agree with that or not is your choice. "Volatile metals" seems to have a more natural meaning of "a metal that is volatile". Polonium is one such. Using it as a group name requires disambiguating it from the natural meaning. Right, that's it from me. That's because I believe there is no need for special names in the first place. To me: names are for families of chemically related elements. Groups are about valence electrons and orbitals. Families are about the final result, sometimes with a dose of natural occurrence (nobody calls Lr a rare earth metal). These can be vastly different as evidenced by hydrogen in group 1 but outside alkali metals. There is no reason why they must follow especially inhomogeneous and small groups like columns in transition metals. In fact the famous family of rare earths in this region includes group 3 but expands well beyond it. So, I don't think I can give feedback about how best to do something that I don't believe is needed. You may disagree, in which case I wish you the best at it. Double sharp (talk) 13:55, 5 August 2020 (UTC) ​G&E (p. 27) refer to the highest normal oxide of each element. Clearly, these are the heptoxides M2O7 for the group 7 metals. I've changed their name to the heptoxide metals. This is for WP, as an encyclopaedia, which we always try to improve. If something we think would be an improvement is not in the literature, we can seek to get it into the literature. Example: the metalloid article was unstable due to disagreement about which elements were metalloids. I wrote an article on this which was published in JChemEd. The result? Our metalloid article is now stable and attained FA status. I've withdrawn the name "Iron group metals" for the reason you gave i.e. that it more often refers to the ferromagnetic metals Fe Co and Ni. "Volatile metals" is in the literature. The “volatile” refers to their low melting points compared to neighbouring metals in this part of the periodic table. Indeed, there is an abrupt and significant reduction in physical metallic character from group 11 to group 12 (Sorensen 1991, p. 3). Special names, didactically speaking, give folks something memorable to hang their hats on. That is why they are useful. --- Sandbh (talk) 07:31, 6 August 2020 (UTC) @Sandbh: G&E quoting the "highest normal oxide" is not a statement about highest oxidation states always being normal. "Normal oxides" means a real oxide with O2− as the counteranion, not peroxide or superoxide. So, K2O, for instance, rather than K2O2 or KO2. Just getting something you think is an improvement into the literature does not mean that you can get it onto WP. If no one but you gives something in the literature, it's simply WP:UNDUE to mention it as something that looks standard on a par with group names like "halogens". See also WP:SELFCITE. It is increasingly my opinion that our colouring is itself not something that we should have done in the first place. Different sources show many different colourings, the colourings give the wrong idea that an element belongs to one and only one category and that they are exhaustive, and picking some sources' view as opposed to others and deciding which is better ourselves is a matter of WP:SYNTH. We can't make arguments on Wikipedia unless you can find them in the literature. It would have been better, in my opinion, to only colour blocks as I do on my userpage, as those are at least generally referred to as a basis even if few actually seem to define them. That will not necessitate any funny business with helium: it can still be an s block element above Ne. The metal-to-nonmetal trend can be mentioned, most of the text present can still be there as bald statements, but we cannot make the decision as to which to believe and colour ourselves with this much variation. And yes, by the way: all those arguments I have been stating in favour of Lu are fair game. They are in the literature, I did not make them up myself, so we can quote them. Double sharp (talk) 07:44, 6 August 2020 (UTC) @Double sharp: Here's the quote by G&E: "…O elicited an increasing valence in the highest normal oxide of each element and this was directly related to group number, i.e. M2O, MO, M2O3,…M2O7." (p. 27) I'll thank you for the courtesy of not treating me as if I were a newbie. I'm well familiar with WP:UNDUE, and with WP:SELFCITE which says, "Using material you have written or published is allowed within reason…". I'm also familiar with Wikipedia's core Ignore All Rules policy, which you recently cited. WP:SNYTH was never raised as an issue, just as we have not had to revert to WP:LAWYERING, until now. Rather, in the spirit of WP:IAR we have always sought to improve WP as an encyclopedia. The colouring of our table is what attracted me to WP in the first place, many years ago. I suspect many other folk find it engaging. The most popular PT on the web is based on our colour-category approach. Our colouring scheme inspired my 2020 peer-reviewed article in Foundations of Chemistry, "Organising the metals and nonmetals" (2,200+ accesses to date). Among other things, the article lists several didactic advantages, including the following: "The accompanying periodic table (see the Electronic supplementary material) incorporates elements of learning theory with its use of annotations to facilitate perceptual grouping; colour to differentiate ideas and direct attention to key topics; and “natural" classes or clusters to organise information and help with content processing (Richey et al. 2010)." We do not engage in the practice of, "picking some sources' view as opposed to others and deciding which is better ourselves". Rather, we strive to show what appears to be the most representative categorisation according to the literature. When a category is finely balanced, as in the roughly 50:50 treatment of group 12, we discussed it and coloured the group as PTM. When it came to astatine, R8R suggested colouring it as a metalloid, which we all supported (= no dissent). I don't understand the basis for your statement that, "the colourings give the wrong idea that an element belongs to one and only one category and that they are exhaustive". Our PT article makes it clear this is not the case. Ditto my JChemEd article. Chemists need not lose sleep over such matters. As Nelson (2011), a chemist, said: "…care needs to be taken to remember that…[this classification scheme] is only an approximation, and can only be used as a rough guide to the properties of the elements. Provided that this is done, however, it constitutes a very useful classification, and although purists often despise it because of its approximate nature, the fact is that practising chemists make a great deal of use of it, if only subconsciously, in thinking of the chemistry of different elements." It seems to me that, with occasional bouts of tethchiness, we strive (as best we can) to take account of the literature. Where the literature is shabby, we do our best to be representative, and discuss and acknowledge the shabbiness in the applicable article. Where one of us feels prompted to address the gap, and put in the sizeable effort to do so, we seek to get published in the literature. There'll be many more arguments in support of La in group 3, when my peer-reviewed article on the location and composition of group 3 soon appears in Foundations of Chemistry (editor Eric Scerri). Sandbh (talk) 13:29, 6 August 2020 (UTC)

@Дрейгорич: That was a great question of yours. I subsequently got an e-mail from a chemistry professor saying "I love this…weather metals, especially!"

No prob. I just had it as a random question in my head. It started with the "disputogens" and I wondered... if we're doing one group of the 18, why not all of them? ― Дрейгорич / Dreigorich Talk 03:27, 9 August 2020 (UTC)

Colleagues, here's the outcome, which I've asked Dr Mark Leach to host at the Internet database of periodic tables. Happy reading. I intend to have the names published in a peer-reviewed journal. Sandbh (talk) 02:58, 9 August 2020 (UTC)

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Representative and transition element (RATE) group names

A colleague asked why none of the transition (technicolour) metal groups have standardised names. "We need better names instead of trying to remember whether nickel is in group 8, group 9, or group 10." They do have standardised names, sort of, in that the IUPAC Red Book (Connelly et al. 2005) provides for them to be called according to the first element in each group, so group 3 is the scandium group. But that is a rather dull practice and I have enough trouble recalling the order of the 3d metals let alone the members of e.g. the cobalt group. Didactically speaking, special names give folks something memorable to hang their hats on. Here is listing of group names, including for the transition elements. Looking at the names now I recall how uninspiring my introduction was to the "no group name" transition metals, many years ago. Group names 1 Li to Fr Hydrogen and the alkali metals 2 Be to Ra Alkaline earth metals 3 Sc Y La Scandium group metals ------------------------------------- 4 Ti Zr Hf Iodide metals 5 V Nb Ta Acid earth metals 6 Cr Mo W Chromatic earth metals 7 Mn Tc Re Heptoxide metals 8 Fe Ru Os Rubiferous metals 9 Co Rh Ir Weather metals 10 Ni Pd Pt Catalytic metals 11 Cu Ag Au Coinage metals 12 Zn Cd Hg Volatile metals 13 B to Tl Icosagens 14 C to Pb Crystallogens ----------------------------- 15 N to Bi Pnictogens 16 O to Po Chalcogens 17 F to At Halogens 18 He to Rn Noble gases Of the above names, only those for groups 1–3 and 15–18 are mentioned in the IUPAC Red Book on the nomenclature of inorganic chemistry. 1 — Alkali metals: Rarely, hydrogen and the alkali metals. Self explanatory, but for hydrogen. Hydrogen is nearly always placed above lithium. Otherwise it is placed floating by itself (sometimes with helium) in the middle of and above the periodic table; above boron, or carbon or straddling boron and carbon; or above fluorine. The position of hydrogen in group 1 is quite well settled. It does not matter that hydrogen is a nonmetal and a gas, in the same way that it does not matter that oxygen in group 16 is a nonmetal and a gas whereas polonium, at the other end of group 16, is a metal and a solid. Similarities of hydrogen with lithium: Both have significant covalent chemistry Lithium, like hydrogen, when bound to highly electronegative atoms such as nitrogen, oxygen, or fluorine, is capable of forming electrostatic bonds with other nearby highly electronegative atoms Their spectra are similar. Similarities with the alkali metals: In chemical reactions, hydrogen and the alkali metals usually lose their single valence electrons; all usually have a valence of +1 Both form similar compounds e.g. hydrogen chloride (HCl) and alkali metal chlorides (XCl) Like hydrogen, most of the alkali metals can form compounds with a charge or oxidation state of –1 Hydrogen can stand in for alkali metals in typical alkali metal structures; see: Hydrogen adopts alkali metal position (Wilson 2013) Hydrogen is capable of forming alloy-like hydrides, featuring metallic bonding, with some transition metals. The anomalous properties of hydrogen can be explained by its unique electron configuration, in that it has no underlying core of electrons. 2 — Alkaline earth metals: Historically, beryllium and magnesium were not counted as alkaline earths (Parish 1977). Beryllium is amphoteric rather than alkaline; magnesium was first isolated, in an impure form, by heating the oxide with charcoal thereby showing it was not an intractable "earth". 3 — Scandium group metals: Scandium, yttrium, and lanthanum were all discovered in mineral samples from Sweden. There is a minor controversy as to the composition of the group. The third and fourth members are either lanthanum and actinium, or lutetium and lawrencium. Most tables show the former although there has been some increasing interest in the latter. There is an IUPAC project considering the matter, here. 4 — Iodide metals: "Van Arkel and de Boer developed the iodide decomposition process [in 1924] to make a pure, ductile metal [Zr] in Eindhoven, Holland. The "iodide crystal bar" process continues to be used today as method of purifying Ti, Zr, and Hf, even thought it is slow and expensive." (Schweitzer 2006, p. 571) 5 — Acid earths: "Although definitely metallic in character in the elementary state, they are decidedly acidic in their normal oxides, the pentoxides. This is true of V, Nb, and Ta at least—and for this reason their pentoxides are also known as the acid earths (i.e., acid-forming metal oxides), or as the earth acids…it appears…the basic character is more strongly developed in Pa than in the first three members of the group, which are not capable of forming simple salts in aqueous solution even with the strongest acids." (Remy 1956, p. 87) 6 — Chromatic earth metals: Etymology: < French chrome, < Greek χρῶμα colour. ^ Chromic acid, of which Cr(III) oxide is the anhydride, has an orange-red appearance † Cr(VI) oxide dissolves in small amounts of water to give yellow-red to red polychromic acids while in larger amounts of water it yield yellow chromic acid solution ‡ Reduction reactions of MoO3 in acid can yield dark red Mo2+4; green-yellow Mo+3; and yellow-orange Mo2O4+2 § On heating, Mo or W metal is transformed progressively into violet to blue-black metallic conducting phases MO3–2 II Tungstite WO3·H2O is formed by the weathering of tungsten containing minerals; it crystallizes in translucent yellow to yellow green masses ¶ Mild reduction in acid medium of WO3·2H2O gives intensely coloured tungsten blue, this being a general term applied to complex mixtures of W(VI) and W(V) oxides and hydroxides # "Thermochromism is the property of substances to change colour due to a change in temperature and WO3 is an attractive example for this property. On cooling the oxide by liquid nitrogen down to –196°C, a sudden change occurs from yellow to white, which then alters to a bluish-white colour between –50 and –27°C. At room temperature it becomes pale lemon-yellow again. On further heating to 200 – 300°C, WO3 becomes dark yellow, changing to a deep orange colour at 400 to 500°C” (Weil & Schubert 2013). ^ Chromic acid, of which Cr(III) oxide is the anhydride, has an orange-red appearance. That chromium is the first of the chromatic earths is apt. Weil M & Schubert W-D 2013, "The beautiful colours of tungsten oxides", Tungsten Newsletter, June, ITAA, https://www.itia.info/assets/files/newsletters/Newsletter_2013_06.pdf, viewed Aug 5th, 2020 7 — Heptoxide metals: "The same probably applies to the triads of elements, between the two halves of large periods; they constitute however the transition between these two halves, between the heptavalent metals of the first half of the large periods, whose highest oxides are acidic…" (Walter 1909, p. 269) Group 7 as the heptoxide metals refers to the observation that this is the first group with exclusively acidic oxides in their highest oxidation state. (The +6 oxides of group 6, while acidic, all show some amphoteric character.) Further, this is the only group in which binary metal heptoxides are found, each such oxide having a unique crystal structure (Mast 2018, p. 5). 8 — Rubiferous metals: (classical Latin rubēre to be red; -fer producing); from the reddish-brown colour of rust; the most prevalent ruthenium precursor being ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO 4(OH)2− 2 formed upon reaction by osmium tetroxide with a base. Iron causes our blood to be red. Iron is the most important structural metal. More than $10 billion is lost each year to corrosion in the US alone. Much of this corrosion is the rusting of iron and steel. The etymology of the word 'rust' has its origins in the Proto-Germanic word rusta, which translates to "redness". That iron is the first of the Group 8 rubiferous metals is a rich juxtaposition. 9 — Weather metals: From the use of cobalt chloride as a humidity indicator in weather instruments; rhodium plating used to "protect other more vulnerable metals against weather exposure as well as against concentrated acids or acids fumes" (Küpfer 1954, p. 294); and the "rainbow" etymology of iridium. 10 — Catalytic metals: "They are…readily obtained in finely divided forms which are catalytically very active." (Greenwood & Earnshaw 2002, p. 1148). Of course, many transition metals have catalytic properties. That said, if you asked me about transition metal catalysts, palladium and platinum would be the first to come to mind. And, per Greenwood and Earnshaw, group 10 appear to be particularly catalytic. 11 — Coinage metals: Historically, most coinage metals (or alloys) are made from copper, silver or gold, the copper usually being augmented with tin and often other metals to form bronze. Roe and Roe (1992) noted 24 metals had been used in coins of the world. Curiously, chromium and manganese were not mentioned by them, even though both elements had been used in common circulation coins (Canada wartime V nickels and US wartime Jefferson nickels, respectively) long before the time of their article's publication. 12 — Volatile metals: The "volatile" refers to their low melting points compared to neighbouring metals in this part of the periodic table. Thus, there is an abrupt and significant reduction in physical metallic character going from group 11 to group 12 (Sorensen 1991). 13 — Icosagens: A reference to the frequency of icosahedral structures seen in this group (Greenwood & Earnshaw 2002, p. 227). 14 — Crystallogens: After the capacity of carbon, silicon, germanium, and grey tin to adopt regular covalent network structures. Rarely adamantogens (Jensen n.d.) or merylides (Fernelius 1971; Fernelius et al. 1983). The origin of merylides is obscure, perhaps mer-, part; -yl, ancient Greek ὕλη (húlē, “wood, material”)" and -ide, one belonging to a specific natural group (Websters 2002), thus charcoal, coal, carbon. On this suggestion, Fernelius et al. (1971) commented that, "It has been proposed, but has not yet become widely used. Let us hope that it never does. New terms should be derived from familiar roots, not unknown ones." 15 — Pnictogens: from pnigmos, suffocation; a reference to the life-extinguishing capacity of nitrogen. 16 — Chalcogens: The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper (the term was also used for bronze/brass, any metal in the poetic sense, ore or coin), and the Latinised Greek word genēs, meaning born or produced. The connection is to the ores that copper forms with sulfur, and to a lesser extent oxygen. 17 — Halogen: The name means "salt-producing". When halogens react with metals, they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide. 18 — Noble gases: Rarely aerogens. Since oganesson is unlikely to be a gas and and is expected to be relatively reactive, perhaps group 18 may need to be renamed as the helium group. † The yellow aspect of the group 6 metals spills over into their neighbours, the heptoxide metals, and iron. Thus the heptoxides of technetium and rhenium are yellow. For manganese, on the other hand, yellow is a rare colour. There are a few references to manganese yellow glassware however the colour arises from the presence of iron rather than manganese per se. Here manganese, as green manganese oxide, oxidises iron from its ferrous (+2) state to its ferric (+3) state yielding yellow iron(III) oxyhydroxide (Corning 2011). References Connelly NG, Damhus T, Hartshorn RM and Hutton AT 2005, Nomenclature of inorganic chemistry: IUPAC recommendations 2005, International Union of Pure and Applied Chemistry, RSC Publishing, Cambridge Corning Museum of Glass 2011, Decolorizers (Manganese dioxide) Fernelius WC, Loening K & Adams RM 1971, 'Names of groups and elements', Journal of Chemical Education, vol. 48, no. 11, p. 730; Fernelius WC 1983, 'Group names', Journal of Chemical Education, vol. 60, no. 2, p. 140. Greenwood NN & Earnshaw A 2002, Chemistry of the elements, 2nd ed., Butterworth-Heinemann, Oxford Grochala W 2020, Watch the colors: or about qualitative thinking in chemistry, open access Jensen WB n.d., The periodic law and table, unpublished article for Encyclopedia Britannica, p. 10 Küpfer YJ 1954, Rhodium uses in plating, Microtecnic, Agifa S.A. Mast, DS 2018, Crystallographic exploration of fundamental technetium species at nonambient conditions, UNLV Theses, Dissertations, Professional Papers, and Capstones 3368 Parish RV 1977, The metallic elements, Longman, New York Remy H 1956, Treatise on inorganic chemistry, vol. 2, Elsevier, Amsterdam Roe J and Roe M 1992, "World's coinage uses 24 chemical elements", World Coin News, Feb. 17, pp. 24–25; Mar. 2, pp. 18–19. Schweitzer PA 2006, Fundamentals of metallic corrosion: Atmospheric and media corrosion of metals, 2nd ed. CRC Press, Boca Raton, p. 571 Sorensen EMB 1991, Metal poisoning in fish, CRC Press, Boca Raton, Florida, p. 3 Walter CW (ed) 1909, Ion, vol. 1: Zeitschrift für Electronik, Atomistik, Ionologie, Radioactivität und Raumchemie, London Websters 2002, A dictionary of prefixes, suffixes, and combining forms Wilson P 2013, Hydrogen adopts alkali metal position, Chemistry World --- Sandbh (talk) 02:58, 9 August 2020 (UTC)

Some arguing

I have decided to remove what used to be here as more heat than light is generated. Even though I still disagree with almost everything Sandbh says about chemistry and his interpretations of the sources, I feel that I went too far again, and I also feel that if something makes me unnecessarily unhappy, I should just stop doing it. So I leave the project instead. Double sharp (talk) 10:14, 7 August 2020 (UTC)

This is very sad news. [1] -DePiep (talk) 10:42, 7 August 2020 (UTC)

@DePiep: My apologies. But I will soon just lack the time due to RL commitments. And even if that was not a consideration, I feel that the general understanding of periodicity is so intertwined with all element articles that I simply will not be able to work here as long as this dispute cannot be resolved. Neither me nor Sandbh will accept the other party's view of the situation and reliable sources, and it's best for my emotional state and real life to just let go and leave. Even if I still think I'm right, why fight? It will make me unhappy.

I have drafted a second RFC on the group 3 dispute. I may still post it for the others who have talked about this, because after over seven months of arguing, they deserve an RFC. But I will not comment on whatever Sandbh posts there. Double sharp (talk) 10:51, 7 August 2020 (UTC)

I understand, incl the wellbeing point. -DePiep (talk) 11:23, 7 August 2020 (UTC)

@DePiep: Thank you. ^_^ Double sharp (talk) 12:11, 7 August 2020 (UTC)

Since the RL time and situation-inflaming issues apply even to starting an RFC: I will not start one. Goodbye. Double sharp (talk) 14:20, 7 August 2020 (UTC)

@Double sharp: As I see it, there is no dispute. I have a view. You have a different view. That happens all day every day all over the world. This doesn't constitute a dispute, unless one or the other of us wants to treat it as such. I've made various proposals within our project over the years. Some got up some didn't. So it goes. I get past the failures, and incorporate what I learnt into my next contribution or project. I'll check with you after a while and see how you're going. Sandbh (talk) 03:27, 8 August 2020 (UTC)

@Sandbh: Well, that's good to hear. Now I focus on my RL work. ;) Double sharp (talk) 04:06, 8 August 2020 (UTC)

@Double sharp: Righto. When you feel like a breather from RL work, or some pop corn for the brain ^_^, feel free to drop by. I'll miss your insights and perspectives, for as long as you decide to un-participate. Sandbh (talk) 05:28, 8 August 2020 (UTC)

@Sandbh: You may still find them at the usual place as long as I'm not around here. I hope, it is not objectionable as a presentation to you. Take it as an opinion piece. ^_^ Right, no hard feelings left on either side I hope. Double sharp (talk) 05:38, 8 August 2020 (UTC)

@Double sharp: Hard feelings don't work for me. They're like an anchor I have to drag around. So yes, absolutely none. Some other people like to drag anchors around so they can have pity parties e.g. or can blame their woes on what a short deal they've got at out life. Not me. Not you, I hope and trust. It's not question of either RL or WP:ELEMENTS. You can have and enjoy both if you choose to do so. "Tears or cantankerous arguments" aren't required. Sandbh (talk) 06:02, 8 August 2020 (UTC)

P.S. you can probably expect me back when IUPAC finally decides on a group 3 constitution. So you may pencil that in. Reason being that that would have to resolve the difference in philosophy that explains why such issues tend to blow up. See you then! XD Double sharp (talk) 21:16, 15 September 2020 (UTC)

Double sharp: I feel no particular philosophy is intrinsically "better" than any other. They all show differing manifestations of periodicity which, as we know, is only ever approximate in the first place. More important is to explain the context for the arrangement of the particular periodic system at hand. It occurs to me that this principle applies to e.g. the location of H and He, and the location and composition of group 3. As you express it, deducing "the properties of the objects being classified from something very basic" and arranging a periodic table on this basis or, say, on wave mechanical grounds, will show some aspects of periodicity and not others seen in different arrangements.

Only an n-dimensional entity would be able to arrange the elements in such a way as to show every manifestation of periodicity. Here, shall we say n = 6^{6^6}. Since we are stuck with the three or four dimensions that we can sense, we have to satisfy ourselves with one slice of this n-dimensional space at a time.

In this context, I doubt IUPAC will make a ruling. I expect they will come up with something like this:

Draft IUPAC Red Book guidance

ELEMENTS IN THE PERIODIC TABLE

The periodic table on the insider cover is the form agreed and used within the IUPAC, rather than being IUPAC recommended or approved. In this instance, the lanthanoids are shown as a 15-element wide series in light of their chemical similarities.

Different forms of the periodic table may be more or less appropriate in particular contexts. For example, a 14-element wide lanthanoid series may be more appropriate to better bring out the concept of an f-block. Such a series could start with, for example, lanthanum or cerium depending on the context.

IUPAC does not recommend or approve any particular format of periodic table or system, nor does it mandate the composition of Groups.

I expect they will still publish the report of the Group 3 project as a fine and informative research paper.

--- Sandbh (talk) 01:05, 16 September 2020 (UTC)

@Sandbh: Well, let's just say we disagree about this. The difference in philosophy about what periodicity really is means neither of us is likely to convince each other, so let's not try till the report comes out. But hopefully you found my linked essay somewhat interesting and hopefully it does not misrepresent you. ^_^ So, I guess you will be rooting for the above outcome, and I will be rooting for an outcome that recommends Lu under Y. I will await the report with interest – incidentally, if you have any indication about when it is likely to come out, I would be interested to hear it – and then make up my own mind about it after reading it. Double sharp (talk) 07:22, 16 September 2020 (UTC)

Double sharp: I won't mind which way they go. After the project completes its report it will go to someone or some committee for approval to publish as an IUPAC report/recommendation suitable for release. This is not guaranteed. Then it would be released for comments by the chemistry community, among others, for (say) six months. Then the comments get considered by IUPAC to see if the project report's recommendation should receive IUPAC endorsement. This is not guaranteed.

I'll ask Eric where things are up to once my article appears online. That would've happened by now but for issues I've experienced with the outsourced (= no accountability; no QA; no coordination) proof production company, and have repeatedly complained about to a cast of a dozen+ people. Finally I rec'd the 6th[!] proof (43 pp) today, and it has only three errors in it, subject to a final read tomorrow. Heavens be, what a saga. Six months to write. I uploaded the MS on 6 Jul. Ten and a half working weeks have passed and the end may be in sight. And the standard response from the proof production company, when you load your MS the first time, is that you only get ONE proof! I've knocked them back five times. I hope I've set a record. There will be a nice old fashioned snail mail formal letter of complaint going to the CEO of the publishing company once this is over.

@Sandbh: Interesting. We'll see what happens, and looking forward to hearing where things are at.

Well, good luck with your publication, and sorry to hear about these problems. ^_^ Double sharp (talk) 10:09, 16 September 2020 (UTC)

Graphic representations etc (Mazurs 1974)

Our alternative periodic tables article refers to a work by Mazurs (1974), called "Graphic representations of the periodic system during one hundred years…". It says:

"A 1974 review of the tables then known is considered a definitive work on the topic:[1] Mazurs, E. G. Graphical Representations of the Periodic System During One Hundred Years. Alabama; University of Alabama Press, 1974, ISBN 0-8173-3200-6."

I deleted:

"is considered a definitive work on the topic:<ref>https://pubs.acs.org/doi/pdf/10.1021/ed052pA436.1".

Double sharp, pre-departure, reverted me, saying "(WP:OR is no good reason to delete that)".

I deleted what I did in the interests of improving WP.

Philip Stewart, a polymath who has published several articles on the PT opined that:

"Mazurs book should be used with great care. He redrew the images, systematically adding elements that were not known when they were first published – which is acceptable – and changing their shape – which is totally unacceptable (for example figure 111 which hideously misrepresents Janet’s elegant original). Sometimes he misattributes them, for example he credits Janet with a design that is not his at all (fig. 85, which is a distorted version of Stedman’s). If he doesn’t like something he simply leaves it out, for example the element zero in tables by von Antropoff and Janet. I do not trust any illustration of Mazurs; you should always check against the original. This is unlike Van Spronsen who is scrupulously accurate.

Mazurs book suffers also from the fact that he classifies the images in a system that is almost incomprehensible, and his bibliography and index are not cross referenced to page numbers, so that it is a heroic enterprise to find anything."

I've experienced the same thing in using Mazurs' book.

Our own article on Mazurs raises similar concerns.

I intend to re-revert Double sharp's edit on the above grounds. I won't do it for now, pending thoughts from others. Sandbh (talk) 06:36, 8 August 2020 (UTC)

@Sandbh: After a quick examination, it seems that doi:10.1021/ed052pA436.1 only mentions "definitive review" as part of a review by George Kauffman. This would appear to be but one opinion about Mazurs' book, and not reflective of the whole community. I would not immediately re-revert, but instead amend it to accredit this statement specifically to Kauffman, and offer the counterargument as you describe with appropriate sourcing.

For instance, change the existing phrasing to: A 1974 review of the tables then known, considered a definitive work on the topic by American chemist George Kauffman, but considered factually inaccurate by polymath Philip Stewart.

Under NPOV, this seems like the best solution, for it gives due credit to those in support of Mazurs' book and those critical of its accuracy. However, since the article presents it in § Further Reading, it might then be more appropriate to keep the description as short and unbiased as possible, and if appropriate, describe it in greater detail in the article body. ComplexRational (talk) 17:40, 10 August 2020 (UTC)

@ComplexRational: Yes, thank you; something like that'd be the way to go. Sandbh (talk) 01:43, 11 August 2020 (UTC)

@Sandbh: In the absence of any objections, should we proceed with this? ComplexRational (talk) 02:28, 13 August 2020 (UTC)

@ComplexRational: For sure we should. Sandbh (talk) 02:34, 13 August 2020 (UTC)

The periodic table: Past, present, and future

Now out.

By Geoff Rayner-Canham

https://www.worldscientific.com/worldscibooks/10.1142/11775

Split d-block

I stumbled upon a transcript of a 1981 Bakerian lecture, here, by RJP Williams who, with CSG Phillips, wrote a remarkable advanced two volume set on Inorganic chemistry, in 1965. From a 1967 book review: "We have inorganic chemistry presented here as the difficult and complex subject it is. The approach is thoroughly adult, and the level is probably more advanced than our students have came to expect."

Williams writes (pp. 362-363):

2. THE CHEMICAL CLASSIFICATION OF ELEMENTS

"The classification of elements in the Periodic Table is now known to be a reflection of restrictions imposed by quantization of energy states of electrons in atoms. However, without recourse to other than empiricism in the study of chemistry the same classification had been observed for over 100 years. In fact it has long been a standard educational practice to separate elements into Groups IA, IIA, and IIIA; transition metals; Groups IB, IIB and IIIB; and the non-metals of Groups IVB to VIIB of the Periodic Table to simplify discussion of their chemistry. Although the distinctive properties in aqueous solution of each of the four classes does not provide sharp divisions it is very useful to treat separately three types of metal: Groups IA, IIA and IIIA metals are associated with equilibrium ionic-model chemistry; transition metals with one-electron redox chemistry and, across each such series, increasingly covalent chemistry concommitant with increasing Lewis-acid strengths of ions, usually at equilibrium with their surroundings; and Groups (IB), IIB and IIIB metal ions with a compromise ion chemistry involving strong Lewis-acid properties while maintaining fast equilibration but little redox activity…Finally, there is the further chemistry of non-metals…"

The upshot is that, according to Phillips, and in the specific context of simple chemistry, a split d block is very useful. --- Sandbh (talk) 03:28, 18 August 2020 (UTC)

The remarkable chemistry of the pre-halogen nonmetals

I have a completed manuscript (5,000 words) if anybody would like to review it pre-publication. --- Sandbh (talk) 00:59, 21 August 2020 (UTC)

A partially disordered periodic table

Here’s a 15-column table which is a hybrid of a Mendeleev 8-column table and an 18-column standard table. The key relocations are the p-block nonmetals to the far left; and the coinage and post-transition metals under their s and early d block counterparts

Taking a leaf out of DIM’s playbook, I ignored atomic number order when this seemed appropriate. It’s refreshing to see the traditional horizontal gaps between blocks disappear. DIM didn’t like these.

Since Dias (2004) reckoned a periodic table is a partially ordered set forming a two-dimensional array, I believe I now have a partially ordered table that is partially disordered twice over.

The table has some curious relationships. Equally, some relationships seen in the standard form are absent. The Group 2, 3, and aluminium dilemmas disappear. This confirms my impression that such dilemmas have no intrinsic meaning. Rather, their appearance or non-appearance is context dependent.

The rest of my explanatory notes and observations follow.

---

Groups 1 to 4 have either a C or F suffix where C (nonmetal) is after the importance of carbon to our existence; and F (metal) is for the importance of iron to civilisation.

Groups 1C and 1F present the greatest contrast in nonmetallic and metallic behaviour.

Coactive nonmetals: They are capable of forming septenary heterogeneous compounds such as C₂₀H₂₆N₄O₁₀PSSe.

Group 2C: Helium is shaded as a noble gas. "Heliox" is a breathing gas mixture of helium and oxygen used in saturation diving, and as a medical treatment for patients with difficulty breathing.

Group 3C: Boron over nitrogen looks odd. Yet one boron atom and one nitrogen atom have the same number of electrons between them as two adjacent carbon atoms. The combination of nitrogen and boron has some unusual features that are hard to match in any other pair of elements (Niedenzu & Dawson 1965).

Boron and phosphorus form a range of ring and cage compounds having novel structural and electronic properties (Paine et al. 2005).

Metalloids: I treat them here as nonmetals given their chemistry is predominately that of chemically weak nonmetals.

Metals: The labels electropositive; transition; and electronegative are adapted from Kornilov (2008).

Group 1F: Monovalent thallium salts resemble those of silver and the alkali metals.

An alloy of cesium (73.71%), potassium (22.14%) and sodium (4.14%) has a melting point of −78.2 °C or −108.76 °F (Oshe 1985).

Silver, copper, and gold, as well as being the coinage metals, are borderline post-transition metals.

Group 2F: Beryllium and magnesium are not in fact alkaline earths. Beryllium is amphoteric rather than alkaline; magnesium was isolated in impure form from its oxides, unlike the true alkaline earths. The old ambiguity over whether beryllium and magnesium should go over calcium or zinc has gone.

Nobelium is here since +2 is its preferred oxidation state, unlike other actinoids.

Group 3F: Aluminium is here in light of its similarity to scandium (Habishi 2010).

InGaAsP is a semiconducting alloy of gallium arsenide and indium phosphide, used in lasers and photonics.

There is no Group 3 "issue" since lanthanum, actinium, lutetium and lawrencium are in the same family.

Gold and aluminium form an interesting set of intermetallic compounds known as Au5Al2 (white plague) and AuAl2 (purple plague). Blue gold is an alloy of gold and either gallium or indium.

Lanthanoids: The oxidation state analogies with the transition metals stop after praseodymium. That is why the rest of lanthanoids are footnoted in dash-dot boxes.

Actinoids: The resemblance to their transition metal analogues falters after uranium, and peters out after plutonium.

Group 4F: It’s funny to see titanium—the lightweight super-metal—in the same group as lead, the traditional "heavy" metal.

This is the first group impacted by the lanthanoid contraction (cerium through lutetium) which results in the atomic radius of hafnium being almost the same as that of zirconium. Hence "the twins".

The chemistry of titanium is significantly different from that of zirconium and hafnium (Fernelius 1982).

Lead zirconate titanate Pb[Zr_xTi_1−x]O₃ (0 ≤ x ≤ 1) is one of the most commonly used piezo ceramics.

Group 5: Bismuth vanadate BiVO₄ is a bright yellow solid widely used as a visible light photo-catalyst and dye.

Steel friends: The name is reference to their use in steel alloys. They have isoelectronic soluble oxidizing tetroxoanions, plus a stable +3 oxidation state. (Rayner-Canham 2020).

Ferromagnetic metals: The horizontal similarities among this triad of elements (as is the case among the PGM hexad) are greater than anywhere in the periodic table except among the lanthanides (Lee 1996). The +2 aqueous ion is a major component of their simple chemistry (Rayner-Canham 2020).

Group 8: "Rubiferous metals" (classical Latin rubēre to be red; -fer producing) is from the reddish-brown colour of rust; the most prevalent ruthenium precursor being ruthenium trichloride, a red solid that is poorly defined chemically but versatile synthetically; and the red osmates OsO
₄(OH)²⁻
₂ formed upon reaction by osmium tetroxide with a base.

Group 9: "Weather metals" comes from the use of cobalt chloride as a humidity indicator in weather instruments; rhodium plating used to "protect other more vulnerable metals against weather exposure as well as against concentrated acids or acids fumes" (Küpfer 1954); and the "rainbow" etymology of iridium.

Group 10: "Catalytic metals" is after a passage in Greenwood and Earnshaw, "They are…readily obtained in finely divided forms which are catalytically very active." (2002). Of course, many transition metals have catalytic properties. That said, if you asked me about transition metal catalysts, palladium and platinum would be the first to come to mind. And group 10 appear to be particularly catalytic.

References

• Dias JR 2004, "The periodic table set as a unifying concept in going from benzenoid hydrocarbons to fullerene carbons", in DH Rouvray & RB King (eds.), The periodic table: into the 21st century, Institute of Physics Publishing, Philadelphia, pp. 371–396 (375)
• Fernelius WC 1982, "Hafnium," J. Chem. Educ. vol. 59, no. 3, p. 242
• Greenwood NN & Earnshaw A 2002, Chemistry of the elements, 2nd ed., Butterworth-Heinemann, Oxford, p. 1148
• Habashi F 2010, "Metals: typical and less typical, transition and inner transition", Foundations of Chemistry, vol. 12, pp. 31–39
• Lee JD 1996, Concise inorganic chemistry, 5th ed., Blackwell Science, Oxford, p. 753
• Kornilov II 1965, "Recent developments in metal chemistry", Russian Chemical Reviews, vol. 34, no. 1, p. 33
• Küpfer YJ 1954, "Rhodium uses in plating", Microtecnic, Agifa S.A., p. 294
• Niedenzu K & Dawson JW 1965, Boron-nitrogen compounds, Springer, Berlin, preface
• Oshe RW (ed.) 1985, Handbook of thermodynamic and transport properties of alkali metals, Blackwell Scientific, Oxford, p. 987
• Paine et al. 2005, "Recent developments in boron-phosphorus ring and cage chemistry", in Modern aspects of main group chemistry, M Lattman et al. (eds.), ACS Symposium Series, American Chemical Society, Washington DC, p. 163
• Rayner-Canham G 2020, The periodic table: Past, present, and future, World Scientific, Singapore

--- Sandbh (talk) 12:18, 27 August 2020 (UTC)

I would readily describe this PT as not being "groupic", but I would not say the same about "our" enwiki PT. (See special:diff/973773980) YBG (talk) 05:40, 1 September 2020 (UTC)

• Nice. If scientifically relevant, do propose & argue for Alternative periodic tables. (I'd say: if structurally new, then add. If editorial variant - forget it). -DePiep (talk) 20:42, 6 September 2020 (UTC)

Lanthanoid vs Lanthanide

The 1985 “Red Book” (p. 45) indicates that the following collective names for groups of atoms are IUPAC-approved: actinoids or actinides, lanthanoids or lanthanides. The note that accompanied that statement explained that although actinoid means “like actinium” and so should not include actinium, actinium has become common usage. Similarly, lanthanoid. The ending “-ide” normally indicates a negatives ion, and therefore “lanthanoid” and “actinoid” are preferred to “lanthanide” and “actinide.” However, owing to wide current use, “lanthanide” and “actinide” are still allowed. http://publications.iupac.org/ci/2004/2601/2_holden.html

Does anybody has a good overview, when exactly IUPAC moved from lanthanide to lanthanoid, while still allowing the name lanthanide for continuity? Was it the 1985 version of the "Nomenclature of Inorganic Chemistry" or was it already done earlier?

The 2005 Version of the Red Book says on page 52: "Although lanthanoid means ‘like lanthanum’ and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending ‘ide’ normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide." On page 311 it says that lanthanide is the anion of lanthanum. --Gunnar (talk) 22:25, 5 September 2020 (UTC)

See the discussion here. Also see this old thread where the almost unanimous consensus was for keeping the -ide naming convention per WP:common usage. Polyamorph (talk) 15:14, 8 September 2020 (UTC)

Thank you for the link to the discussion from 2010, that was interesting. As things tend to change, if is worth while to check if the decision taken years ago is still valid. I don't say that we must revert old decisions, I only say it must not be forbidden to re-evaluate decisions of past. In standardisation we call this stability date: for a given time, a decision (set of requirements) is not touched. After the stability date, the standard is either re-confirmed, reviewed or withdrawn. --Gunnar (talk) 17:12, 8 September 2020 (UTC)

Given that lanthanide remains in the most common use (try a google scholar search of the two terms to see for yourself) I don't see any need to re-evaluate the previous consensus regarding article naming at this time. However, article content discussing the naming convention might require development/updating if new sources are available. Polyamorph (talk) 18:04, 8 September 2020 (UTC)

The original post here in this thread was: "Does anybody has a good overview, when exactly IUPAC moved from lanthanide to lanthanoid"? The detailed discussion weather to say "lanthanide, also called lanthanoid" or "lanthanoid, also called lanthanide" should take place at the relevant article's talk page. And I am happy to review a decision 10 years old, maybe some arguments are seen differently today. I personally are a tiny bit surprised that in the field of science (and chemistry is not a social science, but a rather exact one with clear rules), that the normative power of the professional association that defines the naming conventions has not been respected. --Gunnar (talk) 14:31, 10 September 2020 (UTC)

The discussion can take place wherever the participants choose to do so. Chemistry is not an exact science. It is replete with idiosyncrasies, fuzzy rules, and ignored IUPAC recommendations. Sandbh (talk) 13:41, 17 September 2020 (UTC)

Lining up the periodic table

For reading interest.

48-crash line: Named after the dramatic reduction in physical metallic character after group 11, Cd being Z = 48. Group 12 show few transition metal attributes and behave predominantly like post-transition metals.

Big bang line: H makes up about 73% of the visible universe.

Corrosive line: O, F, Cl = most corrosive nonmetals.

d-fault line: Group 3 show little d-block behaviour; group 4 is the first in which characteristic d-block behaviour occurs.

Deming line: Demarcates the metalloids from the pre-halogen nonmetals. The "reactive" nonmetals to the right of the metalloids each have a sub-metallic appearance (C, O, Se, I).

Edge of the world line: No guesses for this one.

Klemm line: Klemm, in 1929, was the first to note the double periodicity of the lanthanides (Ce to Lu).

Lockyer line: After the discoverer of He, the first element not found on Earth.

Ørsted line: After the magnetic effects believed to be responsible for Mn having a crystalline structure analogous to white P; Tc: First radioactive metal; Re: Last of the refractory metals; "most radioactive" of the naturally occurring elements with stable isotopes. Fe: First of the ferromagnetic metals; Ru: First noble metal; Os: Densest of naturally occurring metals. The number of unpaired d electrons peaks in group 7 and reduces thereafter.

Platypus line: Tl shows similarities to Rb, Ag, Hg, Pb.

Poor metal line: Most metals (80%) have a packing factor (PF) ≥ 68%. Ga: Has a crystalline structure analogous to that of iodine. BCN 1+6. PF 39.1%. Melts in your hand. In: Partly distorted structure due to incompletely ionised atoms. BCN 4+8. PE 68.6%. Oxides in preferred +3 state are weakly amphoteric; forms anionic indates in strongly basic solutions. Tendency to form covalent compounds is one of the more important properties influencing its electro-chemical behaviour. Sn: Irregularly coordinated structure associated with incompletely ionised atoms. BCN 4+2. PF 53.5%. Oxides in preferred +2 state are amphoteric; forms stannites in strongly basic solutions. Grey Sn is electronically a zero band gap semimetal, although it behaves like a semiconductor. Diamond structure. BCN 4. PF 34.0%. Pb: Close-packed, but abnormally large inter-atomic distance due to partial ionisation of Pb atoms. BCN 12. PF 74%. Oxide in preferred +2 state is amphoteric; forms anionic plumbates in strongly basic solutions. Bi: Electronic structure of a semimetal. Open-packed structure (3+3) with bonding intermediate between metallic and covalent. PF 44.6%. Trioxide is predominantly basic but will act as a weak acid in warm, very concentrated KOH. Can be fused with KOH in air, resulting in a brown mass of potassium bismuthate.

Seaborg line: No f electrons in gas phase La, Ac and Th atoms.

Triple treat line: N = gas; S = solid; Br = liquid.

Zigzag lobby: H: needs no intro. Li: Many salts have a high degree of covalency. Small size frequently confers special properties on its compounds and for this reason is sometimes termed ‘anomalous’. E.g. miscible with Na only above 380ºC; immiscible with molten K, Rb, Cs, whereas all other pairs of AM are miscible with each other in all proportions. Be: Has a covalent component to its otherwise predominately metallic structure = low ductility. Lowest known Poisson's ratio of elemental metals. Amphoteric; predominately covalent chemistry atypical of group 2. Some aspects of its chemical properties are more like those of a metalloid.

Zigzag line: Eponymous metal-nonmetal dividing line.

Zintl line: Hypothetical boundary highlighting tendency for group 13 metals to form phases with a various stoichiometries, in contrast to group 14+ that tend to form salts with polymeric anions.

*BCN = bulk coordination number

Sandbh (talk) 13:42, 17 September 2020 (UTC)

Oganesson as a metalloid

Og is predicted to be solid, with a band gap of 1.5 eV. On this basis, it could be expected to have a sub-metallic appearance. The predicted IE is 860 kJ/mol; predicted EA is 5 kJ/mol. From IE and EA, EN is given by

$\chi =(1.97\times 10^{-3})(E_{\rm {i}}+E_{\rm {ea}})+0.19.$

$=(1.97\times 10^{-3})(865)+0.19.$

= 1.89

Given, on this basis, that Og has an intermediate IE (750 to 1,000) and EN (close to 2) and is expected to be a (relatively) reactive sub-metallic looking semiconductor, it appears like it will be a good candidate for admittance into the metalloid club. In any event group 18 will seemingly need to be referred to as the helium group, rather than the noble gases group.

It’ll be a curious arrangement to have metalloids in groups 13 to 16, and 18, but not one in group 17. Astatine would’ve been a semiconductor, and hence counted as a metalloid, but for relativistic effects. Sandbh (talk)

@Sandbh: Commenting to say that I agree with your conclusion, despite coming from a very different philosophy and perspective from yours. (Normally I would continue to not comment here because the different philosophy means our conclusions usually do not match, but since I happen to be looking today and in this case they do match, here we are.) Provided that these predictions are right, I would in my preferred paradigm call oganesson a nonmetal because it would lack the delocalisation in its stable or metastable allotropes that is the one criterion I use, and guess that it looks and behaves something like silicon. As you know, I prefer to divide only between metals and nonmetals, but as you also know almost all the metalloids end up by my criteria on the nonmetals' side anyway (only Sb ends up with the metals), so I am inclined to count this as basically an agreement as I would guess Og to be definitely (although weakly) on the nonmetallic side like Si.

It must of course be noted that I would do this only provisionally, and that there is no substitute for experimental results; it is the excellent agreement with the computations with experiment for the lighter elements that makes me willing to provisionally say this.

To me "noble gases" is not a group name but a family name, so I do not think it has to a priori follow the whole group any more than "alkali metal" has to include hydrogen. Again assuming the predictions are correct, what I would do in my preferred paradigm is rename the category to "noble fluids" (to let in copernicium), and simply let it split across three groups: helium in group 2 (my IIs), neon through radon in group 18 (my VIIIp), and copernicium in group 12 (my XIId). Double sharp (talk) 15:30, 17 September 2020 (UTC)

Double sharp: On the metalloids I have advocated for treating them as chemically weak nonmetals rather than as a unique category of their own. I now recognise it doesn't matter so much how you regard them as long as the context is explained. This principle applies to the treatment of Sb, too. What happens in the literature is that due to e.g. publish or perish or educational curricula or IUPAC recommendations, authors tend to parrot one another, overlooking the benefits of diverse perspectives which, I suppose, tend to be left to the specialist literature.

There is the precedent of referring to the noble gases as the aerogens. The etymology of -gen in this case is < French -gène, ultimately representing Greek -γενής ( < γεν- root of γίγνεσθαι to be born, become, γεννάειν to beget, γένος kind, etc.: see kin). So noble gases are a kind of air, or aerogens.

This sense can be contrasted with the related sense of -gen as "generator", e.g. in the case of halogens as producers of salts. This was extended to chalcogen ("producer of copper ore"). Its further extension to pnictogen ("producer of choking") to describe the nitrogen group is awkward. It involves a change from "producer of a substance" to "producer of an effect", and only describes nitrogen.

Anyway, group 18 could instead be called the octadecagens.

Now, the convention in chemistry is to descriptively name a group according to [1] attributes shared within the group, never mind such attributes may be shared by elements external to the group; or [2] according to the nature of its progenitor e.g. pnictogens after the suffocating nature of nitrogen. For [1] there are many examples of nominative attributes shared by elements external to the Group:

• yttrium is an alkaline earth.
• nickel is a coinage metal.
• volatile metals is a good enough name for the group 12 metals relative to metals in this part of the table. Yet the alkali metals are even more volatile in their own part of the periodic table (cf alkaline earth metals or rare earth metals).
• nitrogen, relatively speaking, is a noble gas (that was how it was regarded pre- the discovery of the group 18 noble gases).

When I refer to "convention" in chemistry, I say this recognising chemistry is replete with idiosyncrasies, fuzziness, and instances of ignoring IUPAC recommendations.

Group 1 seem to be OK referred to as hydrogen and the alkali metals or H and the alkali metals or the H-alkali metals ("halkali metals"?) with the option of leaving out the H, if only the AM proper are being considered. Or go the whole honk'n' hog as hydroalkali metals, treating H as a unique kind of metal, noting the alloying capacity of H and its capacity to stand in for alkali metals proper in some compounds.

The noble fluids are presumably a sub-category of the noble elements (metals and nonmetals)? Is N included here?

Good fun eh? Sandbh (talk) 01:22, 18 September 2020 (UTC)

@Sandbh: Yes, good fun. Anyway for me it's just a hobby, so I did the above to my taste. Therefore I just answer your question about my category. ^_^ No, for me noble fluids are a category in themselves, I don't want to include the so-called noble metals because they are quite happy to stay in compounds once they're already in one. That's the same reason I don't want to include nitrogen there. I had in mind rather the typical instability of Kr and Xe compounds (even XeF₂ is strong fluorinating agent) as a guide for what should be considered noble. Yes, radon may be ambiguous because RnF₂ seems rather stable and it has been seriously proposed to get rid of Rn in air by reacting it away, so I wait for future experiments with interest. So, unless there are any more questions, I'll leave you to discuss categorisation with the others for the time being again. ^_^ Double sharp (talk) 07:37, 18 September 2020 (UTC)

P.S. Maybe indeed I should consider the placement of radon as a noble fluid to be questionable. It would fit with how I generally view polonium as a chalcogen and astatine as a halogen; they are so only sort of. Double sharp (talk) 15:37, 24 September 2020 (UTC)

On chemical natural kinds (Scerri 2020)

doi:10.1007/s10838-020-09511-9

Abstract: A critique of LaPorte's views on chemical kinds, like jade and ruby, is presented. More positively, a new slant is provided on the question of whether elements are natural kinds. This is carried out by appeal to the dual nature of elements, a topic that has been debated in the philosophy of chemistry but not in the natural kinds literature. It is claimed that the abstract notion of elements, as opposed to their being simple substances, is relevant to the Kripke–Putnam approach to natural kinds and to some criticisms that have been raised against it, although I do not support the K–P account. The proposed view avoids the traditional microstructuralist approach to natural kinds. The article also addresses the question of whether natural kinds concern metaphysical or epistemological considerations. Recent attempts by chemists to modify the periodic table are brought to bear on the question of classification and consequently on whether the identification of elements is interest dependent.

The location and composition of Group 3 of the periodic table

I am pleased to note my article has been now published in Foundations of Chemistry, here (open access). About has been about nine months in the making; I only signed off on the (eighth) proof, last night. The acknowledgements section includes the following credit: "I thank…members of Wikipedia’s WikiProject Elements for their indefatigable stress-testing of an early draft of this article." Sandbh (talk) 05:19, 24 September 2020 (UTC)

Congratulations! At last it's online!--R8R (talk) 05:37, 24 September 2020 (UTC)

My sincere congratulations too on getting published. My apologies if I am still not convinced, though. ^_^ Double sharp (talk) 08:41, 24 September 2020 (UTC)

That is fine. Happy reading and brow raising! Sandbh (talk) 12:48, 24 September 2020 (UTC)

Yes, it was indeed an engaging and thought-provoking read. Double sharp (talk) 20:17, 24 September 2020 (UTC)

P.S. Added to my list of articles that mention or discuss the question. And flagged as quite long and collecting various arguments. ^_^ So, looking forward to hearing about the IUPAC project's progress. Double sharp (talk) 09:17, 24 September 2020 (UTC)

Will do. Sandbh (talk) 12:48, 24 September 2020 (UTC)

One of the authors I cited, Simon Cotton, has asked me if his book title could be corrected. In the reference list it shows as "Lanthanoid and actinoid". The right title is "Lanthanide and actinide".

Another of the authors I cited, Eugen Schwarz, has advised me of an egregious error of my own making. Wherever I refer to Ligshitz I should have referred to Lifshitz. He also asked me if it would be possible to replace "(Eugen Schwarz, pers. comm. 8 Dec 2019)." with "(Dogon & Pyykkö 2017)."

The reference details are: Dognon, J-P., Pyykkö, P. Chemistry of the 5g elements: Relativistic calculations on hexafluorides. Angew. Chem. Int. Ed. 56, 10132–10134 (2017)

I asked Springer to make these corrections as they make no difference to the citability of the doi. The have, of course, declined to do so. While the eight-proof nightmare concluded the dead have arisen as I run into the Springer Wall of Obstinacy. Sandbh (talk) 03:29, 25 September 2020 (UTC)

Congratulations!! What a shame you could't get those final fixes, but as you say, it is unsurprising. If I recall correctly, this is not your first effort dealing with a journal publisher. To what do you attribute the experience? Are there any lessons learned that would be worth sharing? YBG (talk) 06:22, 25 September 2020 (UTC)

Extending electronegativities to superheavy Main Group atoms

A few surprises; Here. Sandbh (talk) 05:34, 24 September 2020 (UTC)
Pinging Double sharp.

@Sandbh: Interesting article, but I do not agree at all with the new values for most elements. Electronegativities of Ar through Rn are too high (should be closer to those of S through Po). Ne is OK, but He should be lower than O. All chemical indications are that astatine is more metallic than iodine and the EN value should be lower, not higher as Karol gives. Radon is clearly also less electronegative than xenon (RnF₂ is mostly ionic), but Karol gives a higher EN value. Francium should be more electronegative than caesium, but Karol gives it as less electronegative. The 7p elements also seem to have way too high values: flerovium is a pseudo-shell closure, so Mc through Og values should be a lot lower (chemical intuition suggests Og around Si value at very most, and quite likely lower). Perhaps some aspect of the problem is the considering of 7s-electrons for the superheavies when from Fl onwards they should be too deeply buried to actually use. I know EN rises with oxidation state, so could the inflated EN values be a consequence of using s-electrons implying a chemically unreasonably high oxidation state? That would explain why the only new values I find somewhat reasonable are for the not-yet-discovered 8s elements: 119 with value of K and 120 with value of Ba seems at least plausible.

@Droog Andrey: What values would you give elements 119 and 120 on your scale? I previously guessed 0.83 and 0.96 on the grounds of the Pauling EN values listed at ununennium and unbinilium, but would definitely prefer to have you opine. ^_^ Double sharp (talk) 09:15, 24 September 2020 (UTC)

@Double sharp: I agree.

Karol does not provide a clear explanation as to why EN values should go up in the later superheavy p-block elements. He says:

"However, the monotonic drop in electronegativities proceeding down any group column reverses as the heavy elements are approached. This is most likely a reflection of relativistic effects in which the valence electrons are drawn in closer to the nucleus and are more difficult to “move”.

Is he saying that as the valence electrons are drawn in closer to the nucleus that atomic radii therefore reduce and therefore that the nuclear charge is more strongly "felt" and that therefore EN goes up?

I could buy that.

This does not square so well with astatine, for example. Astatine is more metallic than iodine yet iodine has an Allen EN of 2.36 whereas At is supposedly 2.5

Nor with Te (2.16 and Po (2.27) whereas we know Po forms cation in aqueous solution whereas Te does not.

Nor with Xe (2.58) and Rn (2.74), where Rn has been reported to exhibit cationic behaviour.

Something is not working here. And Karol does not shed any light on it.

I am surprised he got past referees without one of them picking up on this.

OTOH, the values for 119 and 120 are more plausible.

I've asked Eugen for his take on this since he brought Karol to my attention. Sandbh (talk) 07:08, 25 September 2020 (UTC)

@Sandbh: Relativistic effects for Og (for example) will lower energy level of 7s and 7p_1/2 but not of 7p_3/2 which is raised. And by the way the splitting is so large that it doesn't really make sense to refer to single p-orbital energies. And 7s here is lowered so much that it really should just not be counted as valence at all. Electronegativity rises with increasing oxidation state, and so I could buy these only as not-relativistic-enough values for hypothetical group-oxidation-state compounds of these elements (Nh^III, Fl^IV, Mc^V, Lv^VI, Ts^VII, Og^VIII) that, thanks to relativity, have actually no chemical relevance at all because these oxidation states are unreachable. (Except Nh^III which should still be possible as NhF⁻
₄, but a better EN value should rather reflect the more common +1 state.) That also explains partly the too high values of the 6p elements that are for not-very-common high oxidation states. This problem doesn't affect 7s and 8s as badly: just comparing comparable theoretical values, indeed Karol ends up with EN(Fr) > En(Cs) (although I think Ra can very well be below Ba), but then he mixes spectroscopic measurements with theoretical calculations in Fig. 2. Incidentally, Karol presented Fricke's extended table wrongly in an older article of his in the same journal (Chemistry International).

I'll stick with Droog Andrey's electronegativity values, myself. Although 119 and 120 don't have values yet. ^_^ Double sharp (talk) 09:16, 25 September 2020 (UTC)

Lead PT in PT article

Periodic_table

I've updated the PT in the lead of our PT article to make it more of a showcase. Please let me know how it looks. It's a jpg for now. My aim was for a better accommodation of the Ln/An; a readable legend; better use of space; restoration of the halogen terminology in some way; and a balanced look.

The noble metals are not caret-ed. The pre-halogen nonmetals are not explicitly flagged. The Notes section at the right of the legend adds a few nuances.

This is a fair summation of the literature, as we have shown it to date. I'll continue to advocate for a merge of groups 1 and 2, and Al; and for a more formal carving out of the pre-halogen nonmetals. --- Sandbh (talk) 05:05, 25 September 2020 (UTC)

@R8R, YBG, DePiep, and ComplexRational: Sandbh (talk) 07:14, 25 September 2020 (UTC)

I would merely prefer that La and Ac are colored back as a lanthanide and an actinide, respectively, because that's a part of our well-established coloring scheme. I don't think this would be particularly controversial since the existing scheme has been in place for a long while now and since we normally discuss any changes to it. My comments other that this one can wait until I have finally responded to the last Sandbh's message on the proposal to reform the coloring scheme.--R8R (talk) 07:45, 25 September 2020 (UTC)

+1 Double sharp (talk) 09:16, 25 September 2020 (UTC)

Agree with R8R. (I have reverted the edit, see below). -DePiep (talk) 09:30, 25 September 2020 (UTC)

@R8R, Double sharp, DePiep, and YBG: Oh! I forgot that one. Easily fixed. Sandbh (talk) 10:38, 25 September 2020 (UTC)

Legend style options

A few comments

• The AM cells do not appear to be the same color as their legend, but maybe that is an optical delusion on my part. At any rate, everything should match the enwiki color scheme until we change it.
• The two color bands for the lanthanoids and actanoids are truly superb. I'd say it makes this the best job of shoehorning 32 columns into 18. Much better than the grawlix. Great job!!!!
• I think the notes are much too detailed for a chart in the lede; I would leave them out unless there is a consensus to include them.
• I find the horizontal bars in the legend distracting. You could accomplish the same thing by moving the text closer to the colorbox.
• Here are some alternate layouts for the notes that include only a few lines; and some of these options would work well even without the lines I have shown.

---

Style #1: Single-row, mega categories on bottom

Alkali

Alkaline earth

Actinide

Lanthanide

Transition

Post-transition

Reactive

Nobel gas

Metals

Metalloids

Nonmetals

Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined.

---

Style #2: Single-row, mega categories on top

Metals

Metalloids

Nonmetals

Alkali

Alkaline earth

Actinide

Lanthanide

Transition

Post-transition

Reactive

Nobel gas

Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined.

---

Style #3: Double-row, mega categories on top

Metals				Metalloids		Nonmetals
Alkali   Alkaline earth	Actinide   Lanthanide	Transition   Post-transition				Reactive   Nobel gas
Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined.

---

Style #3: Double-row, mega categories on bottom

Alkali   Alkaline earth	Actinide   Lanthanide	Transition   Post-transition				Reactive   Nobel gas
Metals				Metalloids		Nonmetals
Notes: †: F–I = halogen nonmetals H, C, N, O, P, S, Se are sometimes called 'biogen', 'CHONPS', 'orphan' or 'other' nonmetals.   The chemical properties of these elements have not been determined.

— YBG (talk) 08:55, 25 September 2020 (UTC)

re YBG, legend styles (this preferably be discussed in a single dedicated section, but alas). The catgegories in two-row is ill advised, because it suggests another, different hierarchy, as if there is a subordination. While the full horizontal order it greatly and helpfully supports the trend! This even applies to the Ln-An order, how inviting it may be (Ln and An is not a vertical, subordering nature; it's just periods). BTW, is there any reason two rows are needed? As a detail: I think it helps and simplifies when the word 'metalloid' is repeated.

User:YBG, do I understand you prefer the 'color bands' above 'grawlix' (asterisks) as placeholder? If so, I do not agree. The astersisks do have a graphical function (not chemically), being placeholder for the graphic displacement of a set. The displacement should be clarified, not just a "find this out yourself" (like an incomplete IKEA guidepaper). As it happens, using one and two asterisks strengthens the two-row essence nicely. It could look less elegant to some, but that should not overrule a useful solution. Also, we should keep in mind that the 18-column variant is an editorial variant, not a scientific one; created for convenience(?) or old-habit. -DePiep (talk) 09:49, 25 September 2020 (UTC)

{@DePiep: On reflection, I realize that the asterisks serve an important function for accessibility which the color bands do not provide. But coloring the placeholder spaces makes the correspondence more obvious. It would be interesting to see what it looked like with the asterisks. YBG (talk) 14:55, 25 September 2020 (UTC)

Good point, YBG. I see it has been addressed in later version. -DePiep (talk) 07:55, 26 September 2020 (UTC)

Comments (continued)

• I have reverted this change in periodic table. Please, Sandbh, strive for consensus here first. Apart from the many detailed (i.e., unrelated) changes not fleshed out, there also is the more general like what is the reason to make the changes (improvement?), and why would we leave the "general enwiki preferred presentation" we have. -DePiep (talk) 09:28, 25 September 2020 (UTC)

• I find it strange that it has not been achieved to unify AE and AEM into a single category. To me, from a little distance, it seems to be the least controversial change proposed in the last ten years, scientificaly based. Only a naming issue left. § Unification of AM and AEM. Note that I do not propose that merge, I propose a clean result of that discussion. Meanwhile, other proposed changes were added and removed at random these weeks. -DePiep (talk) 09:56, 25 September 2020 (UTC)

  I beg to differ on this one. Sorry to keep you all waiting for my response.--R8R (talk) 10:46, 25 September 2020 (UTC)

@YBG:Thanks for the tremendous feedback YBG, including the suggested legend formats. I’ll look at these closely. One thing to consider, I suspect, is the desirability of making the legend legible within the size of the lead box. Sandbh (talk) 10:33, 25 September 2020 (UTC)

@YBG: I believe I like something along the lines of scheme #3. Sandbh (talk) 11:07, 25 September 2020 (UTC)

@DePiep and YBG: Under the circumstances, there was no need for a revert, especially by a fellow project member. There was no requirement to strive for consensus here first; that’s why we have WP:BOLD. I posted the new PT further to recent discussions within our project. Straight after I explained my design intent and sought comments. You can see the resulting good feedback. Thank you for your support of a Group 1-2 merge. There are three of us now. Sandbh (talk) 10:52, 25 September 2020 (UTC)

... is the opposite of what I said. I am explicitly not !voting for the AE-AEM merge, I noted that the "easiest", less controversial and most science based change did not achieve consensus. For the other changes: yes, you can go B. I declare them controversial/no consnsus so R. And here we are, at D. -DePiep (talk) 11:07, 25 September 2020 (UTC)

@DePiep and YBG: OK so just myself and YBG are advocating for a merge of Groups 1 and 2. There is ordinarily no need for R. D will get the same result. Sandbh (talk) 11:29, 25 September 2020 (UTC)

@DePiep: I alerted other professional non-WP colleagues (~80) with an interest group in periodic table and chemistry education matters, by sending them a link to the PT article. A pity the R now makes it look like I did not know what I was talking about. Would you consider undo your R please, pending the next iteration? Sandbh (talk) 11:41, 25 September 2020 (UTC)

re: no it does not look like that, and I see no need to turn it that way. As I described, the changes are without consensus. That's all. I added that the discussions are random and chaotic, and I still do not see why independent topics are not discussed and concluded independently. Why is there not a start describing what is wrong with current presentation, or up for improvement? -DePiep (talk) 12:31, 25 September 2020 (UTC)

(ec) @Sandbh: Where is the AE/AEM proposal + conclusion? All I see is § Unification of AM and AEM meandering away from its title & topic (into nonmetals even), while not concluding. Anyway, I am getting tired of this way of "discussing" (what happened to the WT:ELEMENTS examplary habits?), and pulling Non sequitur 'conclusions'. -DePiep (talk) 11:43, 25 September 2020 (UTC)

@DePiep: If you had been following the discussion about AE/AEM you would not have to ask me this question. You expect me to do your homework for you. You are quick to object and revert, after people like me have put in the hard yards, without understanding the context for what you object to or revert. As you do not follow the converstations, the result is that you are part of the problem, not the solution. I will no longer put up with this unhelpful WP:CIVIL behaviour of yours and from now will call it as I see it, including at WP:ANI. What happens here is a product of what people put into it. You can like it, lump it, or make your contributions. If you are getting tired of this way of discussing things within our project you can leave anytime, and free up the rest of us to get on with it. Sandbh (talk) 05:55, 26 September 2020 (UTC)

@Sandbh: What makes you think I did not follow the discussion? (BTW, I read your post as a personal attack, and not containing *any* argument). In fact, you implicitly admit you used non-existing conclusions, admitting by the changes you made to you proposal today. Some explicitly following my remarks. Also, I can point you to my(!) constructive contribution when I noted that the AE-AEM merge is 'easy' to achieve; a note you have incorporated. -DePiep (talk) 08:14, 26 September 2020 (UTC)

@R8R, YBG, DePiep, ComplexRational, and Double sharp: I've updated the lead periodic table. Comments welcome. DePiep please do not R. This table is based on what I understand, based on comments made here, to be consensus by R8R, YBG, Double sharp, and myself. D please if you still have concerns. Sandbh (talk) 13:12, 25 September 2020 (UTC)

Sandbh Please list where you prove consensus for each of the detailed changes. -DePiep (talk) 13:25, 25 September 2020 (UTC)

@Sandbh: Looks pretty good overall, though I still have a few comments:

• I'm not aware of any common use of the term "halogen nonmetals" as said in the legend; every source I know simply calls them "halogens", so I'd think it better to stick to that.
• I would not support a merger of groups 1 and 2, because to my understanding, their chemical characteristics are somewhat different and this is reflected in the majority of sources I've read.
• Because of the terminology involved, I feel it is more confusing to readers to say "La and Ac wear two hats", simply because of the visual disconuity of TM–14 Ln/An–9 TM and the idea that La and Ac would not be part of the categories to which they lend their name. I don't think average readers want to get embroiled in the Group 3 debate, and neither should we. A simple PT should not reflect a lack of consensus both on WP and in the scientific community, so we can display group 3 as is, but leave Ln as 57–71 and An as 89–103.
• As far as formatting, was it your intention to have groups 11 and 17 noticeably wider than the rest?
• I also think the table looks better with an external border (not just the ones between element cells).

If I see anything else, I'll add it to this list. ComplexRational (talk) 13:33, 25 September 2020 (UTC)

As has been pointed out half a dozen times, "halogens" is used for group 17 full stop. Injecting the term into the categories, as a venn-description, is not helpful (such details cen be in the dedicated article or section, say halogens). In general, Sandbh nor any other editopr has explained let alone convinced why these details should be added to the first and foremost PT in enwiki. -DePiep (talk) 15:01, 25 September 2020 (UTC)

I apologize but no. That's a common misconception. The term "halogens," strictly speaking, is not about the group, it's about a set of elements in that group. The difference is element 117, tennessine: it is not a halogen by default (as a group 17 element), it may be one or it may not be one depending on what properties it will display once somebody checks. The thinking in the field is that it won't be a halogen (see also note b in tennessine). The Red Book defines the set as consisting of F, Cl, Br, I, and At, rather than as a synonym of "group 17 element" (granted, the book was written before element 117 was first synthesized, but still their definition is on per element basis). The same also applies to every other group label in Template:Periodic table except those for groups 1 and 2, which may hint that maybe getting rid of those names would be better for an encyclopedia, or maybe we could use a comment or a note instead to clarify this if we do want to keep these group names nonetheless.--R8R (talk) 16:16, 25 September 2020 (UTC)

(OK. A very smart and sensitive response, worth rethinking). -DePiep (talk) 22:04, 25 September 2020 (UTC)

That's not a given I think. I agree with R8R's point of view that "halogen" and "group 17" are something different: to me, the former implies some common properties, that it is a category. That such a category must be united by some properties (although good luck finding what the properties are and whether the properties define the category or are just things an already defined category's members have in common). And I can show examples with titles like "Astatine: Halogen or Metal?"" But is that what IUPAC thinks? They talk about "collective names for like elements" indeed, rather than saying "groups". But in 2005 excluding Ts doesn't mean anything because it's not a thing yet. If it had been discovered, would they have excluded it? I can't possibly answer that and neither can anyone who wasn't involved in writing that passage in the 2005 Red Book. Indeed IUPAC itself has later in 2016 referred to "new elements of the halogen and the noble gas groups": that's the recommendation that gave us "tennessine" and "oganesson" rather than "tennessium" and "oganessium". So, is "halogen" a group or a category? I don't think we should issue such a warning that halogen as the whole group 17 is a misconception because the literature is not clear about that. Even if I agree that it's not a good conception. I also don't think we should say outright that they are the same either. That's of course about what is done on Wikipedia. Anyway, here is the text from the Red Book:

“ The groups of elements in the periodic table (see inside front cover) are numbered from 1 to 18. The elements (except hydrogen) of groups 1, 2 and 13–18 are designated as main group elements and, except in group 18, the first two elements of each main group are termed typical elements. Optionally, the letters s, p, d and f may be used to distinguish different blocks of elements. For example, the elements of groups 3–12 are the d-block elements. These elements are also commonly referred to as the transition elements, though the elements of group 12 are not always included; the f-block elements are sometimes referred to as the inner transition elements. If appropriate for a particular purpose, the various groups may be named from the first element in each, for example elements of the boron group (B, Al, Ga, In, Tl), elements of the titanium group (Ti, Zr, Hf, Rf), etc.

The following collective names for like elements are IUPAC-approved: alkali metals (Li, Na, K, Rb, Cs, Fr), alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra), pnictogens⁸ (N, P, As, Sb, Bi), chalcogens (O, S, Se, Te, Po), halogens (F, Cl, Br, I, At), noble gases (He, Ne, Ar, Kr, Xe, Rn), lanthanoids (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (Sc, Y and the lanthanoids) and actinoids (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr).

The generic terms pnictide, chalcogenide and halogenide (or halide) are commonly used in naming compounds of the pnictogens, chalcogens and halogens.

Although lanthanoid means ‘like lanthanum’ and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending ‘ide’ normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide.

---

⁸ The alternative spelling ‘pnicogen’ is also used.

”

Not planning to comment on the proposed changes now, sorry. I do not have the time to do so and only remark here because I was summoned to the previous discussion. Maybe later, or maybe not. ^_^ Double sharp (talk) 22:23, 25 September 2020 (UTC)

@Sandbh: I think DePiep's revert was perfectly fine, and I agree with it. It follows WP:BRD perfectly, which your restoration does not. The fact that you notified 80+ others is immaterial. You can re-notify them with a link to the graphic or with a link to a particular archived version. I think the best thing for you to do would be to self-revert. I myself will not revert it, but I would support anyone else who wishes to do so. I find these specific problems with your graphic

1. Your inclusion of the information about "pre-halogen nonmetals" and "halogen nonmetals" is more detail than belongs in the lede.
2. Furthermore, it reeks of promoting your own hobby horse that has not achieved a clear consensus.
3. Inserting it as an image makes it impossible to guarantee that the color scheme is consistent with the WP:ELEM color scheme
4. Inserting it as an image makes collaboration by editing impossible.
5. Inserting it as an image makes you the gatekeeper of any changes to it.
6. Together these make it seem as though this edit is an attempt at WP:OWN. Having spent years collaborating with you, I am quite sure this is not true, but the appearance is there. It should have come as no surprise that your edit was reverted. I repeat my statement above: it would be best if you self-revert your change.

DePiep brings up an important point that our discussions have been disjointed. I will own up to having been a major contributor to this problem. When I have been away from this page and see 20+ edits, I try to find the best place to insert my comments. Much of my recent editing has been on my phone. The small screen plus the lack of section links makes it very difficult for me to see context and so I have been the biggest contributor to the topic drift especially in the AM+AEM discussion. For that I beg the forgiveness of my friends here at WP:ELEM. YBG (talk) 14:50, 25 September 2020 (UTC)

Well described, YBG. As for the last paragraph: no need to look for 'blame'; from here (from any moment actually) we still can reorganise the multiple independent discussions so that each can conclude crisply by itself. -DePiep (talk) 14:56, 25 September 2020 (UTC)

When I wrote +1 above, I simply meant to express agreement with R8R that La and Ac should be coloured as members of their eponymous categories (Ln and An). That's been standard for a while, it is what IUPAC defines the Ln and An as, and I don't see any consensus to change that. R8R also mentioned that he has some other comments that are pending his response to some comments above, and I would rather wait for him to write them before I decide whether to say something about the other proposed changes. My apologies for not expressing this clearly. Double sharp (talk) 15:12, 25 September 2020 (UTC)

Thanks, Double sharp. But actually our "talk & make consensus" conference here has died. -DePiep (talk) 21:26, 25 September 2020 (UTC)

• Again, Sandbh: [2]: Please list where you prove consensus for each of the detailed changes. -DePiep (talk) 21:36, 25 September 2020 (UTC)

@DePiep: Why is it that within our project, when there is an effort to improve something based on discussion, you shoot first and ask questions later rather than discuss first? Sure, there is BRD and I would've thought that would be the option of later or last resort rather than first choice.

Regarding consensus, the sequence of events was roughly 1. In the context of discussion within our project, I updated the graphic. 2. I told WP:ELEM about it and why. 3. R8R and DS asked for a minor easily accommodated change, that is all. 4. YBG suggested some other really cool options for the legend. 5. I took these comments by R8R, DS and YGB as indicating consensus for the change, subject to some modifications, which I enacted. 6. CR chimed in saying he was basically happy with the graphic, and provided some comments which I just read now, and will look at again.

How much more support do I need before being able to interpret these comments as consensus? Consensus does not require unanimity.

You expressed some concerns and decided to revert on this basis, even though consensus does not require unaniminity. Our project does nor revolve around and is not contingent upon, your concerns. You are entitled to express them here. In WP:CIVIL terms I object to your drive by shoot first (twice in this case) and ask questions later approach, without doing your homework. Sandbh (talk) 04:18, 26 September 2020 (UTC)

@YBG: You decide to get the boot in. Apparently aspects of my graphic "reek" of "promoting my own hobby horse" and not obtaining clear consensus, In fact you reproduced these aspects in your legend suggestions! And what is it about colours in the image? Do you think the current graphic does any better? And still more about inserting it as an image makes collaboration by editing impossible; inserting it as an image makes me the gatekeeper of any changes to it; and together these make it seem as though this edit is an attempt at WP:OWN.

What a load of Australian cobblers. Collaboration impossible eh? What do you call how I incorporated your legend option #3 into the graphic? I am the gatekeeper eh? Let us ban all graphics out of gatekeeper concerns. You are right in your experience of collaborating with me over the years, which has been productive and enjoyable. So why the need to stoke to fire in the first place? What do you reckon that gained. WP:CIVIL?

Why is it necessary to waste time on this drivel? Not on the creative aspects, but on reverting and needing to re-explain one's actions. What happened to an assumption of good faith? Do we have to go "ready-aim-fire" each and every time? Is their no room for "ready-fire-aim", based on good faith and an iterative collaborative approach to improvement? Sandbh (talk) 04:26, 26 September 2020 (UTC)

@Sandbh: As I have re-read my post, I see that I used some intemporate and uncivil language; "reek" immediately jumps out. Please forgive me this.

What I was trying to say is that I believe you are being collaborative, but that these points together could make it appear that you are taking a WP:OWN attitude. I believe we should not only not take ownership, but also bend over backwards to not appear to take ownership.

(And I believe that we should not only be civil, but bend over backwards to avoid appearing to be uncivil. In that I failed.)

My two main concerns are

1. I fail to understand why there should be so much detail in the legend for a lede graphic. The lede, after all, is meant to be a high level summary. If something must be said (and I am not convinced that it is needed), why not just use something like in for the caption: "Authors differ in many aspects of the periodic table: the placement of hydrogen, in the placement and composition of group 3, in the membership of the different categories, and in how many categories they recognize." This would leave the legend to be simply a legend. Anything more seems to me to be highlighting minutae that does not belong in the lede.
2. Secondly, I am unwilling to trust my eyeball judgement that these colors match those of our {{element color}}. There are many places where colors could get skewed in the process of creating graphics.

YBG (talk) 06:10, 26 September 2020 (UTC)

@YBG: later on we can check adherence to {{element color}}. Dropping the AE-red is a good choice for access reasons. -DePiep (talk) 08:20, 26 September 2020 (UTC)

@Sandbh: re you [=me] shoot first and ask questions later rather than discuss first?: misrepresentation. You have had all the space and time to make proposals & reach consensus. But instead you made bold edits with changes some not even discussed, some not fleshed out, and some opposed -- by itself not wrong, but then opposition is to be expected. That is why I reverted, after the WP:BOLD you invoked yourself: straight BRD. You still have not pointed out consensus for the changes. While we are at it, I sense a lot of WP:OWNership in here, and WP:AUTHORITY. -DePiep (talk) 07:54, 26 September 2020 (UTC)

I want to be clear about what I said. I didn't express support for the new picture by Sandbh. I gave it merely a brief look and I thought it was fine in accordance with WP:BOLD, if we take the issue of coloring La and Ac aside. I expected I would have to give more comments in the future (I had yet to formulate them), but only one thing needed to be pointed out quickly. The statement I made does not imply my support. This statement does not imply my opposition, either. I have simply not looked closely enough yet. There seem to be more problems with the picture and the addition of the picture has been reverted, something I have not assessed, either.--R8R (talk) 10:18, 26 September 2020 (UTC)

I want to also be clear that my "+1" indicated support for what R8R said. I had not looked closely enough yet to decide if I supported or opposed the change at the time I wrote that: I simply saw that the issue of colouring La and Ac was something that needed to be pointed out and agreed with R8R. Double sharp (talk) 11:02, 26 September 2020 (UTC)

Latest proposed iteration

The 18-column form of the periodic table, showing the position of Ce−Lu and Th−Lr between groups 3 and 4, in periods 6 and 7. A detailed interactive version is found in § Overview below, and an interactive 32-column form, after § External links.

​​​​​ I did the following:

1. checked the legend colours for matching (YBG)
2. checked the column widths (CR)
3. added a dagger to group 3 and adjusted the legend (CR)
4. changed the group 17 dagger to a double dagger
5. added an external border (CR)
6. added Z numbers to the Ln and An colour bands (DS; YGB).

A few remaining items of interest:

1. I gather YBG remains somewhat concerned about the note re H, C-N, P-Se
2. What to refer to F−I as: halogens or halogen nonmetals?
3. R8R has hinted maybe we could merge AM-AEM and mention the group names in the note
4. ComplexRational is not so sure about such a merge.

--- Sandbh (talk) 04:08, 26 September 2020 (UTC)

---

Version 2 merges groups 1 and 2, and provisionally calls them "unnamed" metals, pending something more acceptable. Included are notes re:

• the status of H and the rest of the non-halogen-non-noble nonmetals; and
• which elements are AE and AEM. Sandbh (talk) 05:22, 26 September 2020 (UTC)

More remaining items of interest:

5. Too much details for overview image (YBG)

6. Legend in two (three) rows is confusing and gives wrong suggestion (DePiep)

-DePiep (talk) 08:01, 26 September 2020 (UTC)

• I note that the AE-AEM merge was not concluded in § Unification of AM and AEM, and R8R has made explicit objections even in this thread. I find it disappointing, and frustrating the discuss-process, that such a change has not been fleshed out before being implemented here. -DePiep (talk) 08:33, 26 September 2020 (UTC)

@DePiep: I am disappointed and frustrated and exasperated that you are unable to consider an idea without it being discussed, processed, and fleshed out before being posted here. Now that I’ve posted it here, discussion, processing, and fleshing can follow. Do you understand what I am saying? Sandbh (talk) 11:09, 26 September 2020 (UTC)

@Sandbh: Please do not take my "+1" reaction to R8R's post as a sign that I have no other objections to this change. I do. I was not originally planning to comment here, but the cat is out of the bag since I already wrote the +1, so let's just do it. So let me just say what I think. And I try to do it very civilly.

Number one. I don't see why we should have such notes at all for the different categorisation possibilities. There are tons of possible categories (pnictogens, chalcogens, rare earth metals, noble metals) and I don't see why the category {H, C, N, O, P, S, Se} is so much more important than these others that it must be mentioned in the lede periodic table.

Number two. I really hesitate to say this for fear of re-provoking the holy war. But there is really no way around it, so again, let me try to do it as civilly as possible. These differences in categorisation are not to my knowledge a serious debate in the scientific community: everyone seems to have no problem going their own way, and there has been no IUPAC project to determine which elements belong to which category, and to my knowledge no one is calling for IUPAC to settle it. Yet some are listed in detail in the footnotes. And yet, such a prominent argument in the literature as to the very composition of group 3 that has such a IUPAC project is not apparently worth mentioning at all in the footnotes. Even though this dispute exists even for people who don't show any colour categories at all. In fact it seems to be outright avoided by calling La-Ac "also recognized as transition metals". Without also mentioning that for people who believe in group 3 with Lu in it, this would apply to Lu-Lr. Why is there this difference?

Note that, while I freely admit I did not behave very well when trying to get support for the change to Lu-Lr form here, I did not change the lede to show it. I surely did add some content to the section of periodic table focusing on the dispute that was supporting Lu-Lr, but at least I did it in the section that was relevant. I did not write at length about it in the lede. Please, have a look at the version immediately prior to Sandbh's reversion: even here, with all my added content to the section on the dispute, which is admittedly undue weight given to the argument, there is no trace of the dispute at all in the lede. No: I tried to get it through proper channels, i.e. discussion. I did not do it in a very nice way, but I kept the issue of changing the default to the discussion pages. Not a single periodic table visible in the mainspace was changed by me (you can check).

Now, there was explicitly not any consensus to change things back to Lu-Lr, so I gave up the idea to do that. That's not to say I don't support it anymore: I still very much do. But I don't do it because I have no consensus to do it. And note that I did not do it even though I had a majority at one point (when Officer781 and Dreigorich had chimed in but the denizens of WP:CHEMISTRY had not yet). And that was the correct decision looking at the opposition from WP:CHEMISTRY. I'm not convinced, looking at the above discussion, that you have a majority in favour of what you're suggesting in the notes. And even if you did, I think such a recolouring decision should go through WP:CHEMISTRY as well to confirm if there is a wider consensus for it, other than between half a dozen people who already know each other pretty well (me, you, R8R, DePiep, YBG, CR).

Where are the citations for this? Where is the consensus? Sure, consensus doesn't require unanimity, but (1) how much does a non-unanimous consensus mean if it's literally among six people and (2) do you actually have a consensus in support of the table as you have it? YBG wonders why the notes have to be so detailed, R8R says he has comments pending. Even if the others (I exclude myself as I didn't participate in the earlier stages) agreed with you, you'd only have 3/5 which is not a very strong consensus mandate among five people! Without a clear consensus for such notes in the first place, why are you putting them in the lede section? Here's one short note that I'd support and could be put in the caption: "The table below shows a common layout with colours representing some commonly used categories of elements. Other layouts and other categories are sometimes encountered and are described below." Done. Why go into so much detail in the lede just for the categories you're currently supporting? Instead of for "polyatomic/diatomic nonmetals" which seriously appear in some books that probably copied from Wikipedia when we had them?

I'm not saying that you're pushing a hobby horse, but I really hope you can see why YBG used those words. You don't have a clear consensus, and your proposed categories don't seem to be any steps above other possible ones. Polyatomic/diatomic appear in the literature now; pnictogen/chalcogen appear as IUPAC-approved; rare earths appear as IUPAC-approved. And the whole group 3 dispute that has gotten significatly more recognition than any category dispute thanks to the IUPAC project is totally not mentioned at all. Please, tell me what the difference between these things and the ones you put in is, other than whether you support them or not. If you can find one, then please explicitly say what it is to assuage concerns. And if you can't; well, indeed YBG was not appearing at his most civil, but can you at least see why you're getting such comments?

The bottom line is: we all have our biases. And maybe indeed we should clarify these biases by drawing somewhere exactly how we'd draw the periodic table if we had total editorial control over a project. I did it already. But please: let's not have them affect what we do for Wikipedia. Let's not even give the impression of having them affect what we do for Wikipedia. And note that I'm not saying your bias is affecting you. In fact, I want to hear something about why your proposed categories are more important than others and deserve such a mention in the notes, so that there is a better explanation for why they are the ones being raised up and not others. And then we can get a more complete picture for consensus to either follow or not.

As for the terms themselves: I am very wary of creating two-word phrases even if they are just descriptive because of the rather insidious tendency in English for any short phrase repeated often enough to sound like it is a term in itself. Already "reactive nonmetal" is getting to that level. (Well, reactive compared to what? Anything is reactive compared to neon, but is silicon by itself a "reactive nonmetal"?) Frankly I would rather return to the oldest colour scheme: other nonmetals, halogens, noble gases. Yes, there is astatine, but as I said above there's some use of "halogen" that implies "not a metal" even if IUPAC doesn't do it that way. If IUPAC can say "noble gas group" to include Og, and yet an article can say "Is Element 118 a Noble Gas"?, then I think the old scheme is defensible even if the halogens are taken without astatine. Or maybe even "other metal" to eliminate the wrangling over aluminium and whether it really can be called "post-transition". At least one advantage of "other" category names is that they are obviously not terms in themselves. Yes, I know, Theodore Gray says there should be a better name than "other metals", but: if it's just a should be, and there isn't a clear such better name, then I don't think it's our position to create one.

I'm not interested in creating drama. I would prefer you to read this and think about how you come across and why you got the responses you got, certainly. But if you think this is too far, if the result is a reply similar to what YBG got, then I will simply drop out of the discussion again. Double sharp (talk) 10:03, 26 September 2020 (UTC)