MCQ
Which of the following species is not paramagnetic ?
- A$NO$
- B$CO$
- C$O_2$
- D$B_2$
✓
Answer
The electronic configuration of the given species is as follows:
$\mathrm{O}_{2}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{x}^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{2},} \\ {\pi 2 p_{z}^{2},}\end{array}\left\{\begin{array}{l}{\pi^{*} 2 p_{y}^{1}} \\ {\pi^{*} 2 p_{z}^{1}}\end{array}\right.\right.$
$\mathrm{B}_{2}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{1}} \\ {\pi 2 p_{z}^{1}}\end{array}\right.$
$\mathrm{NO}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{x}^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{2}, } \\ {\pi 2 p_{z}^{2},}\end{array}\left\{\begin{array}{l}{\pi^{*} 2 p_{y}^{1}} \\ {\pi^{*} 2 p_{z}^{0}}\end{array}\right.\right.$
$CO$: No unpaired electron is present in the molecule, therefore, is not paramagnetic.
$\mathrm{O}_{2}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{x}^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{2},} \\ {\pi 2 p_{z}^{2},}\end{array}\left\{\begin{array}{l}{\pi^{*} 2 p_{y}^{1}} \\ {\pi^{*} 2 p_{z}^{1}}\end{array}\right.\right.$
$\mathrm{B}_{2}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{1}} \\ {\pi 2 p_{z}^{1}}\end{array}\right.$
$\mathrm{NO}: \sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{x}^{2},\left\{\begin{array}{l}{\pi 2 p_{y}^{2}, } \\ {\pi 2 p_{z}^{2},}\end{array}\left\{\begin{array}{l}{\pi^{*} 2 p_{y}^{1}} \\ {\pi^{*} 2 p_{z}^{0}}\end{array}\right.\right.$
$CO$: No unpaired electron is present in the molecule, therefore, is not paramagnetic.
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