XeF4 is the first discovered binary compound of a noble gas. When xenon (Xe) undergoes a chemical reaction with fluorine (F2), XeF4 is produced. It's chemical or also called IUPAC name is Xenon tetrafluoride.
Xe +2 F2 → XeF4
This reaction produces a high amount of heat at the time of
formation and so it has been categorized as an exothermic reaction where near
about 251KJ/mol energy releases per reaction.
Xenon tetrafluoride is a white crystalline solid in appearance has density 4.040 g/cm3, molar mass 207.283 g/mol, and melting point 117 °C.
It is soluble in water and hydrolyses at low temperature to
form different compounds like xenon, oxygen, xenon trioxide (XeO3), and hydrofluoric acid (HF).
In this article, we are going to know about the polarity of XeF4 means
whether it is a polar or nonpolar molecule in full detail. But before that, lets
have some ideas about what polar and nonpolar molecules are:
Polar Molecules
Polar molecules are those molecules that have a net dipole
moment and this is possible only if there is an electronegativity difference
between the associated atoms as well as asymmetrical geometry so that the induced
dipole charges do not cancel each other.
There are some
certain conditions for the molecule to be polar i.e. have asymmetrical structure,
presence of lone pair of electrons or electronegativity difference between
central atom to bonded atoms.
Polar molecules have polar covalent bonds or ionic bonds.
They are soluble in water (called hydrophilic) and other polar solvents like hydrochloric acid (HCl), ammonia (NH3), Nitrogen dioxide (NO2) sulfur dioxide (SO2), etc.
Nonpolar Molecules
Nonpolar molecules are considered as pure covalent bond because
it forms by equal sharing of electrons between the atoms in a compound and this
is what covalent bond is known for.
One more case for the nonpolar molecule if the molecules
have symmetrical structure so that the induced partial charges on the individual
atoms nullify each other and the net dipole moment becomes zero.
As these are a pure covalent bond so they are insoluble in
water (called hydrophobic) and other polar solvents but are soluble in nonpolar
solvents like carbon tetrachloride (CCl4), carbon dioxide (CO2), benzene (C6H6)
etc.
Now, Is XeF4 polar or nonpolar? XeF4 is a nonpolar
molecule despite four individual Xe-F bonds are polar. This is
because XeF4 has an octahedral symmetric geometry. The polarity induced on four Xe-F bonds are cancel each other and the net dipole moment becomes zero.
Why is XeF4 a nonpolar molecule? [Detailed Explanation]
As we have already known there are certain conditions for a
molecule to be polar or nonpolar in the above definitions of a polar molecule and
nonpolar molecule. The same things apply here which makes XeF4 a molecule.
In XeF4, there are four fluorine atoms are bonded with a central xenon atom. Also, there are two lone pair of nonbonding electrons are
localized on the central Xe atom.
The Xe-F bonds are polar as the electronegativity difference
between xenon (2.6) and fluorine (4.0) is 1.4. But we know molecular polarity
is a vector quantity which means net polarity is the vector sum of individual
bond dipoles.
According to the VSEPR theory, MX4E2 structured have octagonal electronic geometry which makes XeF4 molecular geometry square planar i.e. the angle between F-Xe-F is 90° (Symmetrical).
The molecule is symmetrical so that all the Xe-F bond
dipoles are opposing each other, as a result, the net dipole charge becomes zero.
But as shown in the above diagram, there are still two pairs of non-bonding electrons that are presence on the central Xe atom which are aligned at 180° so that their effects are also nullified. And there is not any dipole charge presence on the molecule which makes XeF4 a nonpolar molecule.
Check Out: Is XeF2 Polar or Nonpolar?
XeF4 Polar or Nonpolar (Based on polarity determining factors)
These are some of the major factors which are used to determine the polarity of the compounds:
Electronegativity difference
Electronegativity is a kind of force exerted by atoms on their
bonding partners at the time of bond formation. All the atoms have their own
electronegativity value which varies from atom to atom. Some have higher EN value and
some have lower EN value.
The atoms having higher electronegativity value attract the
electrons pair from the bonding partners. It means higher the electronegativity
difference between atoms, the more uneven sharing of electrons takes place. In the
periodic table, the fluorine (F) atom has the highest electronegativity value of 4.0, and
francium (Fr) has the lowest 0.7.
In the XeF4 compound, the electronegativity difference between fluorine
(4.0) and Xe (2.6) is 4.0-2.6= 1.4 which shows the Xe-F bond is polar according to
the Pauli scale.
Molecular geometry
The central atom of XeF4 (Xe) has a total of 12 electrons
localized in the form of 8 as Xe-F bonding and 4 as non-bonding pairs. So, we
have an MX4E2 structure which is according to VSEPR theory, an octahedral
electronic geometry means XeF4 has square planar molecular geometry.
And due to the symmetrical structure, the polarity of the Xe-F bond cancel each other and no dipole charge induced on the molecule.
Dipole moment
The dipole moment is defined as the products of induced charge
and distance of separation between the atoms. It is given as,
Dipole moment = Charge (Q) * distance of separation (d)
Its unit is Debye and denoted by ‘D’. 1D = 3.33564*10-30 C.m,
where C is Coulomb and m is meter.
The dipole moment is the major aspect for any compound to be
polar or nonpolar. All the polar molecules have a net dipole moment and all
nonpolar have zero dipole moment.
XeF4 is a nonpolar molecule so that its dipole moment is 0D
(Zero).
Post a Comment