The perchlorate ion, ClO₄^–, is described by resonance structures.

(a) Draw the Lewis structures that contribute to the resonance hybrid and identify the most plausible Lewis structures by using formal charge arguments. 

(b) The average length of a single Cl—O bond is 172 pm and that of a double Cl=O bond can be estimated at 140 pm. The Cl—O bond length in the perchlorate ion is found experimentally to be 144 pm for all four bonds.

Identify the most plausible Lewis structures of the perchlorate ion from these experimental data. 

(c) What is the oxidation number of chlorine in the perchlorate ion? Identify the most plausible Lewis structure by using the oxidation number, assuming that lone pairs belong to the atom to which they are attached but that all electrons shared in a bond belong to the atom of the more negative element.

(d) Are these three approaches consistent? Explain why or why not.