Azido

Azide is the anion with the formula N−
3. It is the conjugate base of hydrazoic acid (HN₃). N−
3 is a linear anion that is isoelectronic with CO₂, NCO⁻, N₂O, NO+
2 and NCF. Per valence bond theory, azide can be described by several resonance structures; an important one being ${\displaystyle {\ce {^{-}N={\overset {+}{N}}=N^{-}}}}$. Azide is also a functional group in organic chemistry, RN₃. The dominant application of azides is as a propellant in air bags.

...
Wikipedia