For which species are both bonds of equal length?

(P) ${\mathrm{ClO}}_2^{-}$      (Q) ${\mathrm{NO}}_2^{-}$

The $\mathrm{Cl}-\mathrm{O}$ bond length is equal in the molecule of ${\mathrm{ClO}}_2^{-}$ and it can be represented as in the same way, the structure of ${\mathrm{NO}}_2^{-}$ can be given which has the equal length of $\mathrm{N}-\mathrm{O}$.