What is resonance energy?

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

In which of the following pairs is the first one having more resonance energy than the second one?

What will be the resonance energy of $N_2O$ from the following data: $\Delta H_f(N_2O) = 82 \ kJ \ mol^{-1}$. Bond energies of $N \equiv N$,$N = N$,$O = O$,and $N = O$ bonds are $946$,$418$,$498$,and $607 \ kJ \ mol^{-1}$ respectively.

Delocalised molecular orbitals are found in

The two bonds $N=O$ and $N-O$ in $CH_3NO_2$ have the same bond length due to: