Consider the following species: $\mathrm{CN}{}^{+}$, $\mathrm{CN}{}^{-}$, $\mathrm{NO}$ and $\mathrm{CN}$. Which of these will have the highest bond order?

Solution & Explanation

\textbf{Answer:} (B) $\mathrm{CN}{}^{-}$ \textbf{Solution:} Using MOT bond order $=\frac{1}{2}(N_b-N_a)$: $\mathrm{CN}{}^{-}$ ($14$ e${}^{-}$) has bond order $3$; $\mathrm{CN}$ and $\mathrm{NO}$ have bond order $2.5$; $\mathrm{CN}{}^{+}$ has bond order $2$. Hence $\mathrm{CN}{}^{-}$ has the highest bond order.