Which of the following ions does not show resonance?

Two or more similar structures of the same compound can readily inter convertible to one another by pi bond( $\mathrm{\pi }$ ) electrons through conjugation.

EX: ${\mathrm{CO}}_3^{2-}$,${\mathrm{NO}}_3^{-}$,${\mathrm{CH}}_3{\mathrm{COO}}^{-}$

But ${\mathrm{Cl}}^{-}$ don’t show resonance because pi bond electrons not present in it.