Talk:Alpha decay

This is incorrect, please provide a reference

"Alpha decay is the most hazardous form of radiation,"

Gamma rays are more energetic, smaller, cross barriers better and are the most dangerous form of radioactivity from what I've read. No time to give references at the moment.--Voyajer 20:35, 19 January 2006 (UTC)

• Depends how you look at it. If you were exposed to equal amounts of alpha and gamma radiation, the alpha radiation would do you far more harm because gamma rays (like you said) cross barriers better - they go through you without doing much harm. Alpha particles are heavily ionising. The sense in which gamma rays can be called more harmful is that alpha particles are almost entirely obsorbed by a sheet of paper (it's actually how some smoke alarms work - smoke is denser and so blocks the alpha particles in the device), but gamma radiation will travel much further, doing only small amounts of damage over a long period of time. Here's a reference for you: [1]

• Alpha rays however, cannot pass through the skin, and must be inhaled or otherwise introduced into the body through another entrance. In this reference, you will see that it is described as not being able to pass through paper, but it is stopped by skin as well.[2] —Preceding unsigned comment added by 82.44.3.77 (talk) 18:34, 29 January 2008 (UTC) ====2 types of alphy decay====

Alpha decay is a subject matter about two distinct types of radiation involved energy transfer phenomena, which with relation to this article can be categorized (without rational) as normal or "natural" or low to intermdeiate energy or else as part of the high energy "atomic fission" process. However, the physical phenomenon occurring seems to be the same on both occasions with only the release of energy being the significant feature. Thus it may be said that alpha decay processes are matter disasociation processes that can provide very large (extreme?) to moderate release of nuclear energy as the result of nuclear disassociation processes. WFPMWFPM (talk) 22:45, 9 September 2008 (UTC) Incidently, one thing you can say about vandalism is that gives you an idea as to how often an article is patroled.WFPMWFPM (talk) 22:45, 9 September 2008 (UTC)

Accuracy vs. Truthfulness

"Alpha decay is the most hazardous form of radiation,"

I've read it a few times, and, while the statement may be inaccurate (you can sit all day a foot away from an alpha emitter and never be hit by a single alpha particle), I'm not sure it's necessarily false...

The problem here is the definition of hazardous: alpha particles are big, slow-moving, and electrically charged, while gamma rays are tiny, electrically neutral, moving at the speed of light.

Therefore, a single gamma photon has a huge probability of going through a human body as if it didn't even exist (for the same reason why gamma ray shields are made from several inches of solid lead), while you can bet your house that, as long as it can reach the body, an alpha particle will hit the first layer of cells it meets and set up shop right there.

On the other hand, it must be noted that the first layer of skin cells is dead, so external exposition isn't usually cause for concern, and alpha particles are very short-lived in atmosphere, which makes even a few inches of air an effective shield against them.

On the gripping hand, if an alpha emitter (say, plutonium) enters the body, the released particles will happily run around, hunting for electrons.

Each of them needs two to turn into a stable, electrically neutral Helium atom, and we are talking about first-shell electrons here: I'd bet a pizza against an old shoe that alpha particles can strip electrons from a Fluorine atom, if that's all there is around.

If their speed is high enough, though, the electrons they strip from the surrounding atoms won't be able to bond with them: the alpha particle will slow down, but it will remain fully charged, and keep looking for electrons.

That gives them a huge ionizing potential - much more than gamma rays.

Whether that is enough to make them "the most hazardous form of radiation" is debatable... Maybe the article should just refer to the alpha particles page. -- * 2006-01-20 10:23 UTC

Accuracy?

The article says: "Alpha decay is the most hazardous form of radiation". Alpha decay IS NOT a form of radiation, it is a kind of radioactive decay. The forms of radiation are alpha particles, beta particles, gamma and X-rays etc. --V1adis1av 18:31, 20 January 2006 (UTC) ====Tunneling==== George Gamow's concept regarding "tunneling" was not about Alpha decay but rather about how a moving free but charged alpha particle could penetrate an eloectrostatic charge barrier that was higher than the energy level of the moving alpha particle. The phemomenon of alpha decay has to do with how an alpha particle is able to get loose from the rest of the nucleus in the first place. It is noted to occur at four places in the periodic table. 1: the partitioning of EE4Be8, 2: Alternating with B- decay in high excess neutron areas of the 80+ elements, 3: Occurring at all excess neutron levels of the 82+ elements, and 4: Occurring at low excess neutron levels (Starting at 62Samarium) in the lower elememts of the lanthanide series.WFPMWFPM (talk) 11:19, 11 September 2008 (UTC) ===Alpha occurrences=== After the duscovery of Polonium and Radium by the Curies, the Alpha decay Particles of these elements were used to radiate the light elements like beryllium and boron and produce secondary radiation products which were discovered to be neutrons by Chadwick in 1932. Thus the element EE4Be9 was changed to EE4Be8 by Neutron emission and then almost instantly decayed to 2 alpha particles plus a lot of energy. This leads to the concept that the element EE4Be9 essentially consists of 2 alpha (2He4) particles plus a binding neutron. Also in the areas of alternate Beta-Alpha occurrence it leads to the concept every alternate occurrence of beta decay leads to the production of a peripheral alpha particle by accumulating neutron-proton pairs into one alpha particle plus the energy required for alpha emission. In the third case of the broad spectrum of alpha emission particles (Above Z=82), the quantity and type of alpha emission is indicative of the occurrence of an alpha particle creation process that results in an unbalance in the distribution of the excess energy created by the matter to energy conversion process. Finally, in the low end of the Lanthanide series, there is noted to be the occurrence of Alpha particle emissions in the 6th through 11th elements at low levels of excess neutrons, but which does not occur at the end of the series. This, plus the noted loss in stable excess neutron number occurring during the first three elements of the series leads to the concept of an unbalance structural deficiency of some part of the nucleus, which is subsequently corrected by the accumulation of subsequent neutron-proton pairs. WFPMWFPM (talk) 17:00, 28 September 2008 (UTC) ===This subject matter is discussed in Irving Kaplan "Nuclear Physics" Addison-Wesley,1962 (2nd edit) which should be add to the Reference section of the article. WFPMWFPM (talk) 17:11, 28 September 2008 (UTC)

Charge?

I am in an introductory physics class and the question came up as to the charge of the daughter in an alpha decay reaction. We are curious why the equation is not balanced with respect to charge since the alpha particle has a charge of +2. Can someone please explain this? --Forcemasteryoda

Charge is balanced. (A,Z) -> (A-4,Z-2) + (4,2), i.e. the mother nucleus -> the daughter nucleus + alpha. Z is the charge, A - mass number.

I'm clearly missing something. Aren't there 2 more electrons on the left side and the right??

No need to have electrons at all. These nuclei can even be naked (totally ionized). But in the case of neutral atom on the left side (Z electrons, Z protons), we have on the right side two atoms with Z-2 electrons in the daughter atom and 2 electrons in the helium atom (alpha particle). Really, the alpha is naked when emitted, but it gets two electrons from media when stops, and the (A-4, Z-2) atom gives to media two excess electrons and becames neutral again. --V1adis1av 13:33, 11 April 2006 (UTC)

Thank you for your help. --forcemasteryoda

Hi i have a similiar question: For the first equation, there is no charge on uranium, so it is taken to be a neutral atom. After an alpha-decay, shouldn't the thorium be written with a 2- charge? —Preceding unsigned comment added by 220.255.23.69 (talk • contribs)

Hmmm... perhaps it would be less confusing if we wrote it with the electrons:

${}^{2}{}_{92}^{38}{\hbox{U}}\;\to \;{}^{2}{}_{90}^{34}{\hbox{Th}}\;+\;{}_{2}^{4}{\hbox{He}}^{2+}\;+\;{2e}^{-},$

after all if this is the decay of a neutral atom as you say, they must go somewhere. These aren't likely to matter much to a nuclear physicist, however, as they are not part of the nuclear reaction and won't leave the thorium with much energy (I suppose you might say they just drift away ... at least compared to the alpha). She is more likely to think of these as fully ionized or "naked" nuclei (no electrons at all):

${}^{2}{}_{92}^{38}{\hbox{U}}^{92+}\;\to \;{}^{2}{}_{90}^{34}{\hbox{Th}}^{90+}\;+\;{}_{2}^{4}{\hbox{He}}^{2+},$

in which case the equation is obviously balanced! The reason the charge is emphasized on the helium is due to the fact that alpha particles are always emitted as "naked" nuclei. In other words, since the equation is intended to represent a nuclear reaction, atomic electrons are ignored. Hope this helps to clarify. -MrFizyx 16:56, 2 August 2006 (UTC)

Nice! Thanks for your help :)

Reprise 2011

I believe that this (charge balance) concern has not been addressed in the article. The two equations at the start of the article are BOTH inconsistent in their treatment of orbital electons. If the lack of two orbital electrons on the helium atom is to be explicitly noted, then the two excess orbital electrons on the daughter thorium atom should also be noted. This "inconsistency" can be confusing when one attempts to calculate the decay energy from the change in mass from the parent isotope to the daughter isotope. Speaking of which, I propose to add a short section on calculating the alpha decay energy, where this confusion could be dealt with. NitPicker769 (talk) 21:57, 31 October 2011 (UTC)

This issue is becoming more confused. I think we should follow the example of most chemistry textbooks, which generally write nuclear equations without indicating any charges. For example, KW Whitten, KD Galley and RE Davis, General Chemistry 4th edn Saunders 1992 p.1001 writes ²⁰⁴
₈₂Pb
→ ²⁰⁰
₈₀Hg
+ ⁴
₂He
, with a note in the margin that "α-particles carry a double positive charge, but charge is usually not shown in nuclear reactions."

This practice does not imply that the reactant and products are all neutral atoms. Rather the equation describes a nuclear reaction, and electrons are considered as not important. The product atoms may have a net charge which is neutralized in a complex process which difficult to characterize experimentally.

This article before October 2011 had the equation ²³⁸
₉₂U
→ ²³⁴
₉₀Th
+ ⁴
₂He²⁺
. As pointed out above, this is confusing as it is apparently unbalanced and suggests that only the He atom is charged.

The current article has ²³⁸
₉₂U
→ ²³⁴
₉₀Th^2-
+ ⁴
₂He²⁺
. Although this is formally balanced, it is unrealistic as the free 2- ion is very unstable and loses its electrons to the environment immediately.

So it seems best to restore the nuclear equation without any explicit charges, as in many chemistry books and as in this article prior to 2006. We can add a sentence to say that the equation describes the nuclear reaction without considering the electrons, and does not imply that the net charge of the atoms is zero. Dirac66 (talk) 21:51, 21 December 2011 (UTC)

Change to SI units

Shouldn't the speed of alpha particles be in m/s not km/s also it should be stated as the velocity of alpha particles and not the 'speed' 23:22 26 November 2006

Good point; actually it should provide context, i.e. that typical velocity of emitted alpha particle is about 5% of the speed of light (Lachlan, 31/1/07).

• "speed" would actually be the correct term as "velocity" is defined as "speed" in a certain direction. Starkrm 14:19, 28 March 2007 (UTC)

What causes it

The article is kind of confusing in the sense that the top part says it is caused by the electromagnetic force, and lower down it says it's governed by the stong nuclear force. Could it be both? AstroHurricane001 00:03, 6 December 2006 (UTC)

It is sort of both; an alpha emitter has too many protons & neutrons in the nucleus. The strong nuclear force is unable to completely overcome the repulsion between the protons caused by the electromagnetic force. Given protons always repel electrostatically, the strong nuclear force is considered inadquate to prevent this, so in that regard, it IS governed by the strong nuclear force. Hope this helps. Lokster 21:55, 14 February 2007 (UTC)

Is there any understanding of why this decay always produces helium nuclei, and not, say, deuterium or lithium? ==The process of Accumulation of nucleons into an atom involves the accumulation process plus the physical balancing of the activation energy of the atom's constituents. The theory is that an accumulation is made and then any increase in activation energy content is more or less equally divided among the atom's constituents. Alpha decay occurs when the accumulation process results in an increase in activation energy on an alpha particle part of the atom that exceeds (or nearly exceeds) its free energy value and makes it probable to random (binomially time distributed) disasocciation of the loose aapha particle from the nucleus. WFPMWFPM (talk) 19:46, 2 October 2008 (UTC)

I have answered most of these questions in the recent edits. You'd think that emitting a single proton or neutron would be simpler and easier, but because the helium nucleus has such a high binding energy, emitting one actually takes less energy in total than just emitting a proton, neutron, or a deuterium nucleus. Stormwyrm (talk) 00:59, 6 July 2016 (UTC)

Energy vs Half life

I think it would be worth mentioning that (in general) a higher decay energy corresponds to a shorter half life while a lower decay energy corresponds to a longer half life. Again, not always true, but a little more detail in this article would be handy. Anyone agree? (Lachlan, 31/1/07). —The preceding unsigned comment was added by 128.250.54.27 (talk) 01:13, 31 January 2007 (UTC).

Agreed hope to see that in the page as it is worth to study!HarryTian1999 (talk) 04:23, 5 April 2019 (UTC)

toxicity section correction proposed

In the toxicity section, the first sentence does not make much sense and is false according to any decent radioactivity reference), and confuses the following statements. It has also been the cause of a lot of partial or false quotations above. I propose the following change to it (changes in caps):

"RADIOACTIVE NUCLEI THAT EMIT ALPHA PARTICLES are among the most hazardous SOURCES of radiation if these nuclei are incorporated within a human body. As any heavy charged particle, alpha particles lose their energy within a very short distance in dense media, causing significant damage to surrounding biomolecules. On the other hand, external alpha RADIATION is not harmful because alpha particles are completely absorbed by a very thin (micrometers) dead layer of skin as well as by a few centimeters of air. However, if a substance radiating alpha particles is ingested, inhaled by, injected into, or introduced through some skin-penetrating object (shrapnel, corrosive chemicals) into an organism it may become a risk, potentially inflicting very serious damage to the organism's genetic MATERIAL."

The main reason for confusion is that alpha-emitters typically also emit gamma radiation. More fact-checking and improvement for this page is definitely necessary. —The preceding unsigned comment was added by 129.2.40.128 (talk) 18:04, 1 February 2007 (UTC).

wikibug or something similar

With IE 7 on the alpha decay site I see only the following: " Edie Denvir-"Generic blackman, please stop raping me every day at school" Generic blackman-"No bitch, now suck my dick " But with firefox it shows the whole page? Weird. 87.94.138.102 20:27, 1 February 2007 (UTC)

Quantum Mechanics

Do we need a proper explanation of the mechanism behind alpha decay, i.e. discussion of the potential barrier seen inside the nucleus and a quantum mechanical description of the tunneling event? —Preceding unsigned comment added by Mattyp9999 (talk • contribs) 14:41, 22 February 2010 (UTC)

Yes. The math is given in the WP article on the Geiger-Nuttall law, but we need the standard picture of the nuclear potential well, with sinusoidal waveforms on both sides with exponential decay of probability inside the barrier. SBHarris 14:45, 22 February 2010 (UTC)

Beryllium-8

"The lightest known alpha emitter being the lightest isotopes (mass numbers 106–110) of tellurium (element 52)." Wrong. Beryllium-8 also undergoes alpha decay, that being one of the limiting factors of the triple-alpha process. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:53, 28 July 2011 (UTC)

Everything that produces fast helium nuclei, or alpha particles, doesn't qualify as "alpha decay." The fast alphas from ternary fission, for example, are not the same energy or mechanism as in traditional alpha decay, so this is not usually called alpha decay. In Be-8 what you really have is a sort of spontaneous fission that produces two alphas. But the mechanism is also quite different from what happens in heavier nuclei. SBHarris 19:38, 28 July 2011 (UTC)

I think Whoop whoop pull up (almost six and a half years ago; sorry!) has a point here, though; neither mental picture, be it heavy nucleus-like α or heavy nucleus-like SF, fits ⁸Be terribly well, but it is usually considered an α decay in sources. Speaking in favour of that assignment is that fission fragments are quite variable and they are not in ⁸Be. Nonetheless, SBHarris is right to point out that this is not a "normal" α decay and should be treated as exceptional, with more normal examples of α decay such as ²³⁵U being preferable choices for illustration and understanding. Double sharp (talk) 06:50, 22 January 2018 (UTC)

After the quoted words I have added (in August 2017) the sentence Exceptionally, however, beryllium-8 decays to two alpha particles. Dirac66 (talk) 11:51, 22 January 2018 (UTC)

Mass Number != Atomic Number

"An alpha particle is the same as a helium-4 nucleus, and both mass number and atomic number are the same."

Since the nucleon is 2 protons and 2 neutrons it would have a mass number of 4 and an atomic number of 2. 64.114.134.52 (talk) 04:17, 13 August 2011 (UTC)

What was meant is that the mass number of the alpha is the same as that of a He-4 nucleus, and the atomic number of the alpha is the same as that of a He-4 nucleus. I will reword the text to make this clearer. Dirac66 (talk) 02:06, 14 August 2011 (UTC)

150,000,000,000 km/s?

At the beggining of the article says "Alpha particles have a typical kinetic energy of 5 MeV (that is, ≈ 0.13% of their total energy, i.e. 110 TJ/kg) and a speed of 150,000,000,000 km/s. This corresponds to a speed of around 0.05 c." Speed of light is 299,792,458 metres per second according to the article about speed of light, there is an error of many orders of magnitude. — Preceding unsigned comment added by 81.39.153.29 (talk) 10:49, 3 September 2011 (UTC)

Fixed. Dauto (talk) 14:06, 3 September 2011 (UTC)

Nuclear category transition

It is to be noted that an alpha decay transition of a nuclide does not change the (PN) category of the nucleus involved, since the resulting nucleus is of the same (PN) catogory. Therefor the reason for the change must be the occurrence of some kind of unbalance in the structure of the unstable atomic nucleus that can be improved by the shedding of 4 paired nuclei. This is reasoned to occur mostly due to the rising cumulative positive charge condition in the nucleus, which creates a greater force of repulsion on the paired protons of the structure. Then, if 2 of the paired protons can be combined into a helium nucleus configuration, the system can achieve a sufficient amount of free kinetic energy to exit the parent nucleus.WFPM (talk) 12:59, 28 March 2012 (UTC)

It also should be noted that the incidence of alpha particle emission is not an incidence of a nuclear particle splitup (except for EE4Be8) but rather an incidence of a moderating and/or rebalancing of the nuclear structure of certain of the atoms that  were created by the accumulation process in such a manner that they were originally left with a structural and/or electromagnetic force vector unbalance within some portion of the nucleus. And therefor that some of the helium matter in the universe was created by this method of nuclear restructuring.WFPM (talk) 20:06, 29 March 2012 (UTC)

Uses - Americaranium241

Add see __ for details.

I don't know if it is proper form, but adding the link to the usage section as an additional link to describe the household smoke detector. IF it does not appear to be useful, can be removed.

Richard416282 (talk) — Preceding undated comment added 15:26, 26 September 2014 (UTC)

External links modified

Hello fellow Wikipedians,

I have just modified one external link on Alpha decay. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive http://web.archive.org/web/20090224200050/http://www.phy.uct.ac.za:80/courses/phy300w/np/ch1/node38.html to http://www.phy.uct.ac.za/courses/phy300w/np/ch1/node38.html

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

Y An editor has reviewed this edit and fixed any errors that were found.

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—^{cyberbot II}_{Talk to my owner:Online} 13:06, 3 July 2016 (UTC)

External links modified

Hello fellow Wikipedians,

I have just modified one external link on Alpha decay. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive http://web.archive.org/web/20090224200050/http://www.phy.uct.ac.za:80/courses/phy300w/np/ch1/node38.html to http://www.phy.uct.ac.za/courses/phy300w/np/ch1/node38.html

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

Y An editor has reviewed this edit and fixed any errors that were found.

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—^{cyberbot II}_{Talk to my owner:Online} 12:09, 6 July 2016 (UTC)

deleted nonsense about statistics

The article contained the following completely nonsensical text: "One curiosity is why alpha particles, helium nuclei, should be preferentially emitted as opposed to other particles like a single proton or neutron or other atomic nuclei.[note 1] Part of the answer comes from conservation of wave function symmetry, which prevents a particle from spontaneously changing from exhibiting Bose–Einstein statistics (if it had an even number of nucleons) to Fermi–Dirac statistics (if it had an odd number of nucleons) or vice versa. Single proton emission, or the emission of any particle with an odd number of nucleons would violate this conservation law." One way to see that this is nonsense is that proton emission does actually exist.--207.233.86.175 (talk) 16:02, 24 September 2019 (UTC)

Border of alpha-stable nuclides

As nuclides get heavier, they are prone to undergo alpha decay. Here is a list of borders of nuclides that are alpha-stable, and the alpha decay energies (in keV) of nuclides with next many protons:

N	Alpha-stable Z range	Nuclide with next many protons and its alpha decay energy (in keV)	Distance of alpha-stable isotones to beta-stability line
80	Z ≤ 60	141Pm: 229.8	0 (All beta-stable nuclides (except 5He and 8Be) with N ≤ 82 are alpha-stable)
81	Z ≤ 61	143Sm: 43.5
82	Z ≤ 62	145Eu: 99.4
83	Z ≤ 58	142Pr: 307.0	1
84	Z ≤ 52 or Z = 54	137I: 14.7, 139Cs: 664.0	2
85	Z ≤ 54	140Cs: 26.8	3
86	Z ≤ 56	143La: 89.2	4
87	Z ≤ 57	145Ce: 200.1	5
88	Z ≤ 58	147Pr: 307.2	4
89	Z ≤ 59	149Nd: 294.1	5
90	Z ≤ 61	152Sm: 220.5	0 (150Nd)
91	Z ≤ 63	155Gd: 81.5	1
92	Z ≤ 64	157Tb: 178.0	0 (154Sm and 156Gd)
93	Z ≤ 65	159Dy: 478.7	0 (157Gd)
94	Z ≤ 65	160Dy: 437.3	0 (158Gd and 159Tb)
95	Z ≤ 65	161Dy: 342.8	1
96	Z ≤ 65	162Dy: 83.2	0 (160Gd)
97	Z ≤ 66	164Ho: 431.0	0 (163Dy)
98	Z ≤ 66	165Ho: 137.7	0 (164Dy)
99	Z ≤ 66	166Ho: 177.9	1
100	Z ≤ 67	168Er: 551.9	2
101	Z ≤ 67	169Er: 271.9	3
102	Z ≤ 67	170Er: 51.2	4
103	Z ≤ 68	172Tm: 257.8	1
104	Z ≤ 68	173Tm: 119.9	2
105	Z ≤ 69	175Yb: 597.2	3
106	Z ≤ 69	176Yb: 566.8	4
107	Z ≤ 69	177Yb: 242.7	5
108	Z ≤ 70	179Lu: 823.2	2
109	Z ≤ 70	180Lu: 267.1	3
110	Z ≤ 70	181Lu: 304.4	4
111	Z ≤ 71	183Hf: 928.5	5
112	Z ≤ 71	184Hf: 481.3	6
113	Z ≤ 71	185Hf: 304.4	7
114	Z ≤ 71	186Hf: 43.5	8
115	Z ≤ 72	188Ta: 62.1	7
116	Z ≤ 75	192Os: 360.1	4
117	Z ≤ 76	194Ir: 610.3	1
118	Z ≤ 76	195Ir: 234.1	2
119	Z ≤ 77	197Pt: 549.8	3
120	Z ≤ 77	198Pt: 106.2	4
121	Z ≤ 79	201Hg: 331.6	1
122	Z ≤ 79	202Hg: 133.2	2
123	Z ≤ 80	204Tl: 493.9	1
124	Z ≤ 80	205Tl: 155.0	0 (204Hg)
125	Z ≤ 81	207Pb: 392.3	1
126	Z ≤ 81	208Pb: 517.0	2
127	Z ≤ 78	206Au: 136.7	7

Continuation of this table according to this table: N = 128 isotones may be alpha-stable up to Z = 76 (²⁰⁴Os), with ²⁰⁵Ir having an alpha-decay energy of 0.59 MeV; the distance of alpha-stable isotones to beta-stability line is 12 (²⁰⁴Os to ¹⁹²Os). N = 129 ~ 137 could have Z up to 76, 76, 76, 76, 76, 76, 77, 77, 77. Isotopes of Pb, Bi, Po, At may be alpha-stable from N = 144, 150, 154 and 158 (²²⁶Pb, ²³³Bi, ²³⁸Po, ²⁴³At) on. 2A04:CEC0:C027:CAB3:FDCA:A821:45D0:96B4 (talk) 15:12, 20 November 2023 (UTC)

Alpha decay energies of the most stable isotopes of even-Z elements from Po to Fm

A common question is that why Po through Ac are so unstable compared to later elements Th through Cm. The following table may be used to give some intuition; the isotopes listed are all principally alpha emitters (the alpha decay branching ratio is 72.6% for ²¹¹Rn, 96% for ²¹⁰Rn and >99.5% for the others). Notice the Geiger-Nuttall law.

Nuclide	Qα (MeV)	Nuclide	Qα (MeV)	Nuclide	Qα (MeV)
209Po	4.97923	208Po	5.21530	210Po	5.40745
222Rn	5.59031	211Rn	5.96538	210Rn	6.15891
226Ra	4.87062	223Ra	5.97899	224Ra	5.78885
232Th	4.08160	230Th	4.76996	229Th	5.16757
238U	4.26795	235U	4.67826	236U	4.57310
244Pu	4.66555	242Pu	4.98453	239Pu	5.24451
247Cm	5.35348	248Cm	5.16173	245Cm	5.62300
251Cf	6.17580	249Cf	6.29600	250Cf	6.12844
257Fm	6.86355	252Fm	7.15270	255Fm	7.23972

The major decay modes for ²²⁵Ra (β⁻), ²²⁸Ra (β⁻), and ²⁵³Fm (88% EC) are not alpha decay, so these nuclides are not listed. 129.104.241.218 (talk) 14:34, 22 March 2024 (UTC)

Mass excesses measured using mass of ⁴He to show trend of alpha decay energies

Mass number	Isobar with the lowest energy	Atomic mass	m(nuclide) - mass number×(m(4He)/4) (MeV)
1	1H	1.007825031898	6.68274
2	2H	2.014101777844	11.92326
3	3He	3.016029321967	13.11253
4	4He	4.002603254130	0
5	5He	5.012057	8.19988
6	6Li	6.0151228874	10.44951
7	7Li	7.016003434	10.66350
8	8Be	8.00530510	0.09184
9	9Be	9.01218306	5.89239
10	10B	10.01685322	9.63639
11	11B	11.01143260	3.98088
12	12C	12	-7.27475
13	13C	13.003354835336	-4.75597
...
114	114Sn	113.90278013	-159.66984
115	115Sn	114.903344696	-159.75018
116	116Sn	115.90174283	-161.84853
117	117Sn	116.9029540	-161.32657
118	118Sn	117.9016066	-163.18789
119	119Sn	118.9033113	-162.20620
120	120Sn	119.9022026	-163.84518
121	121Sb	120.9038157	-162.94881
122	122Te	121.9030439	-164.27397
123	123Sb	122.9042140	-163.79026
124	124Te	123.9028179	-165.69694
125	125Te	124.9044307	-164.80086
126	126Te	125.9033117	-166.44943
127	127I	126.904473	-165.97392
128	128Xe	127.9035313	-167.45733
129	129Xe	128.9047794	-166.90096
130	130Xe	0129.903508	-168.69149
131	131Xe	130.9050824	-167.83118
132	132Xe	131.9041535	-169.30267
133	133Cs	132.905451933	-168.69942
134	134Ba	133.90450825	-170.18468
135	135Ba	134.90568845	-169.69156
136	136Ba	135.90457580	-171.33422
137	137Ba	136.90582721	-170.77477
138	138Ba	137.9052471	-171.92140
139	139La	138.9063533	-171.49717
140	140Ce	139.9054387	-172.95535
141	141Pr	140.9076528	-171.49916
142	142Nd	141.9077233	-172.03971
143	143Nd	142.9098143	-170.69819
144	144Nd	143.9100873	-171.05012
145	145Nd	144.9125736	-169.34038
146	146Sm	145.913041	-169.51122
147	147Sm	146.9148979	-168.38776
148	148Sm	147.9148227	-169.06404
149	149Sm	148.9171847	-167.47008
150	150Sm	149.9172755	-167.99173
151	151Eu	150.9198502	-166.19964
152	152Sm	151.9197324	-166.91560
153	153Eu	152.9212303	-166.12654
154	154Gd	153.9208656	-167.07249
155	155Gd	154.9226220	-166.04264
156	156Gd	155.9221227	-167.11396
157	157Gd	156.9239601	-166.00867
158	158Gd	157.9241039	-166.48095
159	159Tb	158.9253468	-165.92942
160	160Dy	159.9251975	-166.67472
161	161Dy	160.9269334	-165.66397
162	162Dy	161.9267984	-166.39595
163	163Dy	162.9287312	-165.20179
164	164Dy	163.9291748	-165.39481
165	165Ho	164.9303221	-164.93233
166	166Er	165.9303011	-165.55812
167	167Er	166.9320562	-164.52949
168	168Er	167.9323783	-164.83570
169	169Tm	168.9342133	-163.73262
...
204	204Pb	203.9730436	-148.78044
205	205Tl	204.9744275	-148.09757
206	206Pb	205.9744653	-148.66859
207	207Pb	206.9758969	-147.94129
208	208Pb	207.9766521	-147.84406
209	209Bi	208.9803986	-144.96044
210	210Po	209.9828737	-143.26113
211	211Po	210.9866532	-140.34678
212	212Po	211.9888680	-138.88993
213	213Po	212.992857	-135.78043
214	214Po	213.9952014	-134.20287
215	215At	214.998653	-131.59395
216	216Rn	216.000274	-130.69023
217	217Rn	217.003928	-127.89278
218	218Rn	218.0056013	-126.94034
219	219Fr	219.009252	-124.14596
220	220Ra	220.011028	-123.09786
221	221Ra	221.013917	-121.01300
222	222Ra	222.015375	-120.26111
223	223Ra	223.0185022	-117.95437
224	224Ra	224.0202118	-116.96812
225	225Ac	225.023230	-114.76291
226	226Th	226.024903	-113.81075
227	227Th	227.0277041	-111.80777
228	228Th	228.0287411	-111.44804
229	229Th	229.031762	-109.24032
230	230Th	230.0331338	-108.56872
231	231Pa	231.035884	-106.61316
232	232U	232.0371548	-106.03564
233	233U	233.0396343	-104.33223
234	234U	234.0409503	-103.71262
235	235U	235.0439281	-101.54504
236	236U	236.0455661	-100.62548
237	237Np	237.0481734	-98.80303
...

If I got it correctly, the five N = 82 isotones around ¹⁴⁰Ce have the lowest value of m(nuclide) - mass number×(m(⁴He)/4) among all nuclides, followed by ¹³⁶Ba (-171.33421 MeV) and ¹³⁴Ba (-170.18468 MeV). 103.166.228.86 (talk) 10:21, 18 April 2024 (UTC)

Most negative alpha decay energies

It seems that ⁴⁸Ca has the most negative alpha decay Q value among almost beta-stable nuclides, with Q_α = -13.9765 MeV, and followed by:

• ¹⁴N with Q_α = -11.6122 MeV;

• ⁴⁶Ca with Q_α = -11.141 MeV;

• ²⁹Si with Q_α = -11.1272 MeV;

• ¹⁵N with Q_α = -10.9914 MeV;

• ⁵⁰Ti with Q_α = -10.7172 MeV;

• ¹³C with Q_α = -10.64754 MeV;

• ³⁰Si with Q_α = -10.6433 MeV;

• ²⁶Mg with Q_α = -10.6148 MeV;

• ²³Na with Q_α = -10.47 MeV;

• ⁵¹V with Q_α = -10.2922 MeV;

• ²⁷Al with Q_α = -10.0918 MeV;

• ²⁸Si with Q_α = -9.98414 MeV.

Note that the list above includes all beta-stable nuclides with proton number or neutron number equal to 7 or 14. The other nuclides listed (other than ²³Na) are N = 28 isotones. 14.52.231.91 (talk) 00:33, 16 August 2024 (UTC)

Two regions of nuclides that are highly alpha active

First region: N ≥ 84, N - Z ≤ 23. Most nuclides in this region have alpha decay half-lives shorter than T_α(¹⁴⁷Sm) = 1.066×10¹¹ years, making them very alpha unstable while being "light". This region is due to and reflects the magic number N = 82.

The alpha-stability of the nuclides in this region is approximately indicated by N - Z, for N ≥ 84.

N - Z = 20 (¹⁴⁸Gd: 86.9 y): extremely unstable

22 (¹⁴⁶Sm, ¹⁵⁰Gd, ¹⁵⁴Dy: 10⁶ - 10⁸ y): very unstable

23 (¹⁴⁷Sm: 1.066×10¹¹ y): quite unstable, detectable in the case of ¹⁴⁵Pm

24 (¹⁴⁴Nd, ¹⁴⁸Sm, ¹⁵²Gd: 10¹⁴ - 10¹⁵ y): OK to ignore in pratical use

25 (¹⁴⁵Nd, ¹⁴⁹Sm, ¹⁵¹Eu: 10¹⁸ - 10²² y): quite stable but remains detectable

≥ 26 (> 10²² y): no alpha decay

Second region: Z ≥ 84, 127 ≤ N ≤ 134 plus ²¹¹Bi. Nuclides in this region have alpha decay half-lives shorter than T_α(²¹⁸Po) = 3.04 minutes (considering the fact that ²¹⁸Po is extremely neutron-rich, having a higher N/Z ratio than all stable nuclides), making them the most alpha-unstable known nuclides. The energies released are among the largest of all nuclides. Almost all beta decays are overshadowed by extreme alpha-instability. This region is due to and reflects the magic numbers Z = 82 and N = 126. 14.52.231.91 (talk) 01:34, 16 August 2024 (UTC)

The two regions are clearly visible even for people with no or little knowledge of shell model. For the first region, the instability of ^146,147Sm is obvious, even if they lie between the effectively stable ¹⁴⁴Sm (T_2β+ perhaps > 10²¹ years) and ¹⁴⁸Sm (T_α = 6.3 × 10¹⁵ years), and they each have the lowest energy among their isobars; ¹⁴⁶Sm even has too short half-life to be primordial. For the second region, the nuclides with N = 128,129,130 are astonishingly short-lived. 14.52.231.91 (talk) 00:28, 27 August 2024 (UTC)

An interesting article

I found this interesting article discussing alpha decay. 14.52.231.91 (talk) 00:19, 21 August 2024 (UTC)

Formula for alpha decays

According to [3], alpha decays have $\ln T_{1/2}={\sqrt {2}}\pi \alpha {\sqrt {\dfrac {E_{\alpha }}{Q_{\alpha }}}}(Z-Z_{\alpha })Z_{\alpha }-AZ-B$ for some constants $A$ and $B$, where $\alpha$ is the fine-structure constant, $E_{\alpha }=3727.3794118\,{\rm {MeV}}$ is the energy of the alpha particle, $Q_{\alpha }$ is the Q-value, and $Z,Z_{\alpha }=2$ is respectively the charge number of the parent nuclide and the alpha nuclide. When $T_{1/2}$ is in years, the constants are about $A=0.7749$ and $B=80.285$. Some alpha decay energies:

Nuclide	Qα (MeV)	lg(Tα (y) given by the formula)	lg(actual Tα (y))
8Be	0.09184	-24.87	-23.59
143Nd	0.523	82.83
144Nd	1.9064	17.16	15.36
145Nd	1.5793	24.29
146Sm	2.5288	9.14	7.96
147Sm	2.3113	12.12	11.03
148Sm	1.9869	17.45	15.80
149Sm	1.8713	19.68
150Sm	1.4498	29.94
151Eu	1.9645	18.76	18.66
206Pb	1.1355	66.61
207Pb	0.3924	157.11
208Pb	0.5172	128.79
209Bi	3.1373	15.82	19.30
210Po	5.4075	-2.51	-0.42
211Po	7.5945	-11.98	-7.79
212Po	8.95412	-16.02	-14.03
213Po	8.536	-14.88	-12.99
214Po	7.8335	-12.77	-11.28
215At	8.178	-13.57	-11.50
216Rn	8.197	-13.37	-11.85

14.52.231.91 (talk) 03:11, 29 August 2024 (UTC)

Alpha decays of (almost) beta-stable nuclides with half-lives from 10⁶ to 10²⁵ years

¹⁵⁴Dy: 1.40×10⁶ y;

¹⁵⁰Gd: 1.79×10⁶ y;

²³⁷Np: 2.14×10⁶ y;

^210mBi (almost beta-stable): 3.04×10⁶ y;

²⁴⁷Cm (almost beta-stable): 1.56×10⁷ y;

²³⁶U: 2.34×10⁷ y;

²⁴⁴Pu: 8.01×10⁷ y;

¹⁴⁶Sm: 9.20×10⁷ y;

²³⁵U: 7.04×10⁸ y;

²³⁸U: 4.471×10⁹ y;

²³²Th: 1.406×10¹⁰ y;

¹⁴⁷Sm: 1.066×10¹¹ y;

¹⁹⁰Pt: 4.83×10¹¹ y;

¹⁸⁴Os: 1.12×10¹³ y;

¹⁵²Gd: 1.08×10¹⁴ y;

¹⁸⁶Os: 2×10¹⁵ y;

¹⁴⁴Nd: 2.29×10¹⁵ y;

¹⁴⁸Sm: 6.3×10¹⁵ y;

¹⁷⁴Hf: 7×10¹⁶ y;

¹⁸⁷Os: 4.1×10¹⁶ y - 4.5×10¹⁹ y (predicted here);

¹⁸⁰W: 1.8×10¹⁸ y;

¹⁵¹Eu: 4.62×10¹⁸ y;

¹⁴⁹Sm: 8.3×10¹⁷ y - 9.7×10¹⁸ y (predicted);

²⁰⁹Bi: 2.01×10¹⁹ y;

¹⁷⁶Hf: 2.0×10²⁰ y - 6.6×10²⁰ y (predicted);

¹⁷⁷Hf: 4.5×10²⁰ y - 5.2×10²² y (predicted);

¹⁴⁵Nd: 1.9×10²² y - 4.3×10²³ y (predicted);

¹⁹²Pt: 3.9×10²² y - 2.9×10²³ y (predicted);

¹⁷⁸Hf: 2.2×10²³ y - 1.1×10²⁴ y (predicted);

¹⁵⁶Dy: 3.4×10²⁴ y - 6.8×10²⁴ y (predicted);

¹⁶⁸Yb: 3.4×10²⁴ y - 8.7×10²⁴ y (predicted);

¹⁸⁵Re: 3.4×10²⁴ y - 4.4×10²⁵ y (predicted). 129.104.241.231 (talk) 09:21, 2 October 2024 (UTC)