Question

What are the formal charges of each atom in `ClO_4^-`?

Answer 1

Given a static resonance structure, all of the atoms are neutral, save ONE negatively charged oxygen.

Explanation:

A Lewis structure of `(O=)_3Cl-O^-` is feasible, which places the formal negative charge on oxygen. Of course the negative charged is distributed over all the oxygen centres by resonance. The chlorine atom owns 7 valence electrons, and is thus neutral.