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4.Chemical Bonding and Molecular Structure
hard
${{\rm{H}}{{\rm{e}}_2}}$ molecule is not possible.
Option A
Option B
Option C
Option D
Solution
He $(Z=2)$, So, Total electron in $\mathrm{He}_{2}=4$
Electron configuration in $\mathrm{MO} \mathrm{He}_{2}:\left(\sigma_{1 s}\right)^{2}\left(\sigma_{1 s}^{*}\right)^{2}$
All electron are paired in $\mathrm{He}_{2}$, so it is diamagnetic.
Bond order $=\frac{1}{2}\left(\mathrm{~N}_{\mathrm{b}}-\mathrm{N}_{\mathrm{a}}\right)=\frac{1}{2}(2-2)=0$
Bond order in $\mathrm{He}_{2}$ is zero. So it is unstable and does not exist.
$\mathrm{MO}$ energy diagram of $\mathrm{He}_{2}$ is as under.
Standard 11
Chemistry
