Question

Which of the following molecule(s) is expected to exhibit diamagnetic behaviour?

• A. $C_2$
• B. $O_2$
• C. $N_2$
• D. $S_2$

Answer 1

Answer: (A), (C)

$N_2$

$C_2(6+6=12)$

$=\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,\pi 2p_x^2\approx \pi 2p_y^2$

$N_2(7+7)=14$
$=\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,\pi 2p_x^2\approx \pi 2p_y^2,\sigma 2p_z^2$

$C_2\text{and}{N}_2$, all the electrons are paired, therefore both of are diamagnetic.



$O_2=8+8=16$
$=\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,\sigma 2p_z^2,\pi 2p_x^2=\pi 2p_y^2,{\pi }^{\ast }2p_x^1={\pi }^{\ast }2p_y^1$
$S_2:LL\sigma 3s^2,{\sigma }^{\ast }3s^2,\sigma 3p_x^2,\pi 3p_y^2,\pi 3p_z^2,{\pi }^{\ast }3p_y^1,{\pi }^{\ast }3p_z^1$

Oxygen and sulphur both are paramagnetic molecules due to presence of unpaired electrons.