Question

Azide ion $\left[N_3^{-}\right]$ exhibits an $(N-N)$ bond order of 2 and may be represented by the resonance structures I, II and III given below:

The most stable resonance structure is

• A. I
• B. II
• C. III
• D. All of them have equal stability

Answer 1

The correct option is A I

The structure with more delocalization and more charge separation is the most stable.
$$\begin{array}{cccc}\text{Structure}& \text{Formal}& \text{charge}& \text{on N}\\ & \text{left}& \text{middle}& \text{right}\\ I& -1& +1& -1\\ II& -2& +1& 0\\ III& 0& +1& -2\end{array}$$
Here, structure I has more delocalisation and charge separation and hence it is the most stable among the three.
Structures II and III have equal stability.