Question

In which of the following is the $O-N-O$ bond angle highest ?

• A. $N{O}_2$
• B. $N{O}_2^{+}$
• C. $N{O}_2^{-}$
• D. $N{O}_3^{-}$

Answer 1

The correct option is B $N{O}_2^{+}$

In $N{O}_2$, the hybridisation of $N$ is $s{p}^2$. It has a bent geometry and the bond angle is ${134}^{\circ }$. Due to the repulsion between the lone pair and the bond pair which is more as compared to bond pair - bond pair repulsion, the bond angle is greater than ${120}^{\circ }$.
In $N{O}_2^{+}$, the steric number will be the number of sigma bonds + the number of lone pairs = 2+0=2.
So, the hybridisation is $sp$ and the bond angle is ${180}^{\circ }$.
In $N{O}_2^{-}$, due to $s{p}^2$ hybridisation, the bond angle should be ${120}^{\circ }$. But due to the presence of a lone pair, the bond angle becomes a little less than ${120}^{\circ }$.
In $N{O}_3^{-}$, due to $s{p}^2$ hybridisation and the absence of lone pairs, the bond angle is ${120}^{\circ }$.
Thus, the highest bond angle is in $N{O}_2^{+}$.