In which of the following ionisation processes the bond energy increases and the magnetic behaviour changes…
In which of the following ionisation processes the bond energy increases and the magnetic behaviour changes from paramagnetic to diamagnetic?
- $\mathrm{O}_2 \longrightarrow \mathrm{O}_2^{+}$
- $\mathrm{C}_2 \longrightarrow \mathrm{C}_2^{+}$
- $\mathrm{NO} \longrightarrow \mathrm{NO}^{+}$
- $\mathrm{N}_2 \longrightarrow \mathrm{N}_2^{+}$
Solution
Molecular orbital configuration of
$
\begin{aligned}
& \mathrm{O}_2=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2 \pi^* 2 p_x^1 \pi^* 2 p_y^1 \\
& \Rightarrow \text { Paramagnetic } \\
& \text { Bond order }=\frac{10-6}{2}=2 \\
& \mathrm{O}_2^{+}=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2 \pi 2 p_y^2 \pi^* 2 p_x^1 \\
& \Rightarrow \text { Paramagnetic } \\
& \text { Bond order }=\frac{10-5}{2}=2.5 \\
& \mathrm{C}_2=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \pi 2 p_x^2 \pi 2 p_y^2 \\
& \Rightarrow \text { Diamagnetic } \\
& \text { Bond order }=\frac{8-4}{2}=2 \\
& \mathrm{C}_2^{+}=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \pi 2 p_x^2 \pi 2 p_y^1
\end{aligned}
$
$\Rightarrow$ Paramagnetic
Bond order $=\frac{7-4}{2}=1.5$
$\mathrm{NO}=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2 \pi 2 p_y^2 \pi^* 2 p_x^1$
$\Rightarrow$ Paramagnetic
Bond order $=\frac{10-5}{2}=2.5$
$
\mathrm{NO}^{+}=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2 \pi 2 p_y^2
$
$\Rightarrow$ Diamagnetic
Bond order $=\frac{10-4}{2}=3$
$
\mathrm{N}_2=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_x^2 \pi 2 p_y^2 \pi 2 p_z^2
$
$\Rightarrow$ Paramagnetic
Bond order $=\frac{10-4}{2}=3$
$
\mathrm{N}_2^{+}=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_x^2 \pi 2 p_y^2 \sigma 2 p_z^1
$
$\Rightarrow$ Paramagnetic
Bond order $=\frac{9-4}{2}=2.5$
Bond order increase from $\mathrm{NO}$ to $\mathrm{NO}^{+}$
Asked in: AP EAMCET 2021 (24 Aug Shift 1)
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