Q. Which of the following is paramagnetic?
NTA AbhyasNTA Abhyas 2022
Solution:
A molecule having one or more unpaired electrons in their valence shell is paramagnetic or having an odd electron system is paramagnetic.
MO electronic configuration of $\text{O}_{2}$ is
$\sigma 1 \text{s}^{2} \text{, } \sigma 1^{\star} \text{s}^{2} \text{, } \sigma 2 \text{s}^{2} \text{, } \sigma 2^{\star} \text{s}^{2}$
$\sigma 2 \text{p}_{\text{z}}^{2} \text{, } \pi 2 \text{p}_{\text{x}}^{2} \text{, } \pi 2 \text{p}_{\text{y}}^{2} \text{, } \pi 2^{\star} \text{p}_{\text{y}}^{1} \text{, } \pi 2^{\star} \text{p}_{\text{x}}^{1}$
Due to presence of unpaired electron in ABMO $\pi \overset{\star}{2} \text{px}$ & $\pi \overset{\star}{2} \text{py}$ behaves paramagnetic.
MO electronic configuration of $\text{O}_{2}$ is
$\sigma 1 \text{s}^{2} \text{, } \sigma 1^{\star} \text{s}^{2} \text{, } \sigma 2 \text{s}^{2} \text{, } \sigma 2^{\star} \text{s}^{2}$
$\sigma 2 \text{p}_{\text{z}}^{2} \text{, } \pi 2 \text{p}_{\text{x}}^{2} \text{, } \pi 2 \text{p}_{\text{y}}^{2} \text{, } \pi 2^{\star} \text{p}_{\text{y}}^{1} \text{, } \pi 2^{\star} \text{p}_{\text{x}}^{1}$
Due to presence of unpaired electron in ABMO $\pi \overset{\star}{2} \text{px}$ & $\pi \overset{\star}{2} \text{py}$ behaves paramagnetic.