Question

Which of the following statements is true for azide ion?
A.It can act as a bidentate ligand.
B.Two ${\text{N}} - {\text{N}}$ bond lengths are different in the anion
C.It is isoelectronic and isostructural with ${\text{C}}{{\text{O}}_2}$
D.There are two $\sigma$ and three $\pi$ bonds

Answer 1

We know that azide ion has the formula $N_3^ -$. The number of electrons in the ion is 22, that is, each nitrogen atom contains seven electrons and one extra due to negative charge.

Complete step by step solution:
The azide ion has three nitrogen atoms. Two nitrogen atoms form two bonds each with the central nitrogen atom. As a result the central nitrogen carries a positive charge and both the terminal nitrogen carry a negative charge each.
Azide ion also shows resonance and its resonating structures have an $N - N$ triple bond and an $N - N$ single bond. Thus this structure is more unstable as it contains a nitrogen atom with a $- 2$ charge on it. Thus, it is more reactive and the azide ion acts as a unidentate ligand.Since we know the overall structure of the azide ion, we can say that the two ${\text{N}} - {\text{N}}$ bond lengths are the same. It is a symmetrical and linear molecule.
The total number of electrons in the azide ion is 22. It has 16 electrons in the valence shell.
In ${\text{C}}{{\text{O}}_2}$, the total number of electrons is 22 (six from the carbon atom and eight from each oxygen atom). Also, we know that carbon dioxide is a linear molecule. Thus, we can say that azide ion is isoelectronic as well as isostructural with a carbon dioxide molecule.

Thus, the correct option is C.

Note:
We know that carbon has four valence electrons. In carbon dioxide, carbon is bonded to two oxygen atoms and forms a double bond with each atom. As a result, carbon is ${\text{sp}}$ hybridized and carbon dioxide is a linearly shaped molecule with carbon in the middle and two oxygen atoms on each side.