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Question: Given,\({{He}}_{{2}}^{{{ + 2}}}\) ion is more stable than \({{H}}{{{e}}_{{2}}}\) molecule. Explain....

Given,He2+2{{He}}_{{2}}^{{{ + 2}}} ion is more stable than He2{{H}}{{{e}}_{{2}}} molecule. Explain.

Explanation

Solution

Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that belongs to the noble gas section of the periodic table. It has the lowest boiling point of all the elements. In the observable universe, helium is the second lightest and most abundant element.

Complete answer:
There are only two valence electrons in the He2+2{{He}}_{{2}}^{{{ + 2}}} ion (two from each He atom minus two for the +2 + 2 charge). The molecular orbital diagram can now be filled in.
The two electrons occupy the bonding (σ1s)\left( {{{\sigma 1s}}} \right) orbital, which is the lowest energy molecular orbital, resulting in an (σ1s)\left( {{{\sigma 1s}}} \right) 22 electron configuration. So, the bond order is
= 12[Nb − Na]  = (2 − 0)2 = 22 = 1{{ = }}\,\dfrac{{{1}}}{{{2}}}\left[ {{{{N}}_{{b}}}\,{{ - }}\,{{{N}}_{{a}}}} \right]\,\,{{ = }}\,\dfrac{{\left( {{{2}}\,{{ - }}\,{{0}}} \right)}}{{{2}}}\,{{ = }}\,\dfrac{{{2}}}{{{2}}}\,{{ = }}\,{{1}}
As a result, He2+2{{He}}_{{2}}^{{{ + 2}}} is expected to contain a single He  − He{{He}}\,\,{{ - }}\,{{He}} bond. As a result, it should be a stable species.
Let us take a look at the He2{{H}}{{{e}}_{{2}}} molecules, which are made up of two He{{He}} atoms with the 1s2{{1}}{{{s}}^{{2}}} electronic configuration.
Both the σ1s{{\sigma 1s}} bonding and (σ∗1s)\left( {{{\sigma *1s}}} \right) antibonding orbitals must contain two electrons with a total of four valence electrons. This results in an electronic configuration of (σ1s)2(σ1s)2{\left( {{{\sigma 1s}}} \right)^{{2}}}{\left( {{{\sigma 1s}}} \right)^{{2}}}.
So, the bond order is
Bond order = 12[Nb − Na]  = (2 − 2)2 = 0{{ = }}\,\dfrac{{{1}}}{{{2}}}\left[ {{{{N}}_{{b}}}\,{{ - }}\,{{{N}}_{{a}}}} \right]\,\,{{ = }}\,\dfrac{{\left( {{{2}}\,{{ - }}\,2} \right)}}{{{2}}}\,{{ = }}\,0
The He2{{H}}{{{e}}_{{2}}} molecule has no net covalent bond, indicating that it is not a stable species.

Note:
Cryogenics (the largest single use, accounting for about a quarter of production) uses liquid helium to cool superconducting magnets, with MRI scanners being the most popular commercial use.
Inhaling a small amount of helium temporarily alters the timbre and quality of the human voice, just as it does for any gas whose density varies from that of air.