The changes in bond length with respect to $\mathrm{N}-\mathrm{N}$ and $\mathrm{O}-\mathrm{O}$, when…

The changes in bond length with respect to $\mathrm{N}-\mathrm{N}$ and $\mathrm{O}-\mathrm{O}$, when $\mathrm{N}_2$ becomes $\mathrm{N}_2^{+}$and $\mathrm{O}_2$ becomes $\mathrm{O}_2^{+}$are respectively
  1. increases, decreases
  2. decreases, increases
  3. increases, increases
  4. decreases, decreases

Solution

$ \begin{aligned} \mathrm{N}_2(14) \rightarrow \sigma 1 s^2 < \stackrel{*}{\sigma} 1 s^2 < \sigma 2 s^2 < \stackrel{*}{\sigma} 2 s^2 & < \pi 2 p_x^2 \\ & \approx \pi 2 p_y^2 < \sigma 2 p_z^2 \end{aligned} $ Bond order $=\frac{10-4}{2}=3$ $ \begin{aligned} \mathrm{N}_2^{+}(13) \rightarrow \sigma l s^2 < \stackrel{*}{\sigma} \mathrm{l} s^2 < \sigma 2 s^2 < *{ }_\sigma 2 s^2 < & \pi 2 p_x^2 \\ & \approx \pi 2 p_y^2 < \sigma 2 p_z^1 \end{aligned} $ Bond order $=\frac{9-4}{2}=2.5$ $ \begin{aligned} & \mathrm{O}_2(16) \rightarrow \sigma 1 s^2 < \stackrel{*}{\sigma} 1 s^2 < \sigma 2 s^2 < \stackrel{*}{\sigma} 2 s^2 < \sigma 2 p_z^2 < \pi 2 p_x^2 \\ & \approx \pi 2 p_y^2 < \pi 2 p_x^1 \approx \pi 2 p_y^1 \\ & \text { Bond order }=\frac{10-6}{2}=2 \\ & \mathrm{O}_2^{+}(15) \rightarrow \sigma l s^2 < \stackrel{*}{\sigma} \mathrm{l} s^2 < \sigma 2 s^2 < \stackrel{*}{\sigma} 2 s^2 < \sigma 2 p_z^2 < \pi 2 p_x^2 \\ & =\pi 2 p_y^2 < \stackrel{*}{\pi} 2 p_x^1=\stackrel{*}{\pi} 2 p_y^0 \\ & \text { Bond order }=\frac{10-5}{2}=2.5 \\ & \end{aligned} $ $\because$ Bond order $\propto \frac{1}{\text { Bond length }}$ $\therefore$ In case of $\mathrm{N}_2^{+}$bond length increases as bond order decreases. While in $\mathrm{O}_2^{+}$bond order increases and hence bond length decreases

Asked in: AP EAMCET 2019 (20 Apr Shift 2)

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