Question

Which of the following molecules/species have identical bond order and same magnetic properties?

(I) $O_2$ (II) $NO$ (III) $N_2^{+}$

• A. (I), (II) only
• B. (I) and (III) only
• C. (I), (II) and (III)
• D. (II) and (III) only

Answer 1

The correct option is C (I), (II) and (III)

Bond order and magnetic properties:

(i)$O_2$ - Bond order =$\frac{10-6}{2}=2$

$\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p{z}^2\{\begin{array}{c}\pi 2p{x}^2\\ \pi 2p{y}^2\end{array}\{\begin{array}{c}{\pi }^{\ast }2p{x}^1\\ {\pi }^{\ast }2p{y}^1\end{array}$

Unpaired electrons gives rise to paramagnetism.

(ii) $NO$ -Bond order =$\frac{10-5}{2}=2.5$
$\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p{z}^2\{\begin{array}{c}\pi 2p{x}^2\\ \pi 2p{y}^2\end{array}\{\begin{array}{c}{\pi }^{\ast }2p{x}^1\\ {\pi }^{\ast }2p{y}^0\end{array}$

Unpaired electrons gives rise to paramagnetism.

(iii)$N_2^{+}$ Bond order =$\frac{9-4}{2}=2.5$

$\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p{z}^2\{\begin{array}{c}\pi 2p{x}^2\\ \pi 2p{y}^1\end{array}\{\begin{array}{c}{\pi }^{\ast }2p{x}^0\\ {\pi }^{\ast }2p{y}^0\end{array}$

Unpaired electrons gives rise to paramagnetism.

Ans:- (ii) $NO$ and (iii) $N_2^{+}$

Both have identical Bond orders ($2.5$ each) and the same magnetic properties (paramagnetic).