Chemistry - CHEMICAL BONDING Question with Solution | TestHub

Concepts :

Hund's Rule in MO, Magnetic Moment Formula $(\mu =\sqrt{\mathrm{n}(\mathrm{n}+2)})$, s -p mixing effects.

Solution:

1.Original State ( $\mathbf{B}2,\mathbf{Z}=5,10$ electrons): With $\mathrm{s}-\mathrm{p}$ mixing, the order is ${\sigma }_{1\mathrm{s}}^2{\sigma }_{1\mathrm{s}}^{\ast 2}{\sigma }_{2\mathrm{s}}^2{\sigma }_{2\mathrm{s}}^{\ast 2}{\pi }_{2{\mathrm{p}}_{\mathrm{x}}}^1{\pi }_{2{\mathrm{p}}_{\mathrm{y}}}^1$

Number of unpaired electrons (n) = 2.

${\mu }_{\mathrm{i}nitial}=\sqrt{2(2+2)})=\sqrt{8}B.M.$

2.  Perturbed State (Non-mixing order): The sequence becomes ${\sigma }_{1\mathrm{s}}^2{\sigma }_{1\mathrm{s}}^{\ast 2}{\sigma }_{2\mathrm{s}}^2{\sigma }_{2\mathrm{s}}^{\ast 2}{\sigma }_{2{\mathrm{p}}_z}^2$

Number of unpaired electrons (n) = 0.

${\mu }_{final}=0B.M.$

3.  Change:

$$\Delta \mu =0-\sqrt{8}=-\sqrt{8}B.M.$$