1)

Which one of the following molecules is expected to exhibit diamagnetic behaviour?


A) $C_{2}$

B) $N_{2}$

C) $O_{2}$

D) $S_{2}$

Answer:

Option A,B

Explanation:

C2 (6+6=12)=  $\sigma 1s^{2},\sigma ^{*}1s^{2}, \sigma 2s^{2},\sigma ^{*}2s^{2},\pi2p_x^2=\pi 2p_y^2$

 Since all the electrons are paired, it is a diamagnetic species.

 N2  (7+7=14)  $\sigma 1s^{2},\sigma ^{*}1s^{2}, \sigma 2s^{2},\sigma ^{*}2s^{2},\pi 2p_x^2=\pi 2p_y^2, \sigma 2P_{z}^{2}$

 It is also a diamagnetic species because of the absence of unpaired electrons.

 O2    (8+8=16)

or   S2 =   $\sigma 1s^{2},\sigma ^{*}1s^{2}, \sigma 2s^{2},\sigma ^{*}2s^{2},\sigma 2p_{z}^{2},\pi2p_{x}^{2}=\pi 2p_y^2 $

$\pi ^{*}2p_{x}^{1}=\pi ^{*}2p_{y}^{1}$

 Due to the presence of two unpaired electrons, O2  and S2 both are paramagnetic molecules.