The inflation of an "air bag" when a car experiences a collision occurs by the explosive decomposition of sodium azide, NaN$_3$, which yields nitrogen gas that inflates the bag. The following resonance structures can be drawn for the azide ion, N$_3$:
$[\ddot{N}=N=\ddot{N}]^- \leftrightarrow [\ddot{N} \equiv N-\ddot{N}]^-$
$\uparrow$
$[\ddot{N}-N \equiv \ddot{N}]^- \leftrightarrow [\ddot{N}-\ddot{N}=\ddot{N}]^-$
Identify the best and two worst structures (select three overall).
$[\ddot{N}=N=\ddot{N}]^-$, Best
$[\ddot{N} \equiv N-\ddot{N}]^-$, Best
$[\ddot{N}=N=\ddot{N}]^-$, Best
$[\ddot{N}-N \equiv \ddot{N}]^-$, Best
$[\ddot{N}=N=\ddot{N}]^-$, Worst
$[\ddot{N} \equiv N-\ddot{N}]^-$, Worst
$[\ddot{N}=N=\ddot{N}]^-$, Worst
$[\ddot{N}-N \equiv \ddot{N}]^-$, Worst
