What is the number of Lewis structures for $NO_2^{-}$?

Given that:
$(i) \Delta_f H^o$ of $N_2O$ is $82 \ kJ \ mol^{-1}$
$(ii)$ Bond energies of $N \equiv N, N = N, O = O$ and $N = O$ are $946, 418, 498$ and $607 \ kJ \ mol^{-1}$ respectively.
The resonance energy of $N_2O$ is $...... \ kJ \ mol^{-1}$.

Draw the resonance structures of $N_2O_5$,state its shape,and indicate the bond angles and bond lengths.

Explain the important aspects of resonance with reference to the $CO_{3}^{2-}$ ion.

For which of the following can resonance structures be drawn? Why?
$CO_2, NO_2, O_3, O_2, CH_4$

Use the following data to answer the question below.
Calculate the resonance energy of anthracene in $kcal/mol$.