Two alternate Lewis structures can be drawn for the perchlorate ion, ClO₄⁻
CHEMISTRY · Single correct · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Two alternate Lewis structures can be drawn for the perchlorate ion, ClO₄⁻.
I. All four Cl–O bonds are single, and chlorine obeys the octet rule.
II. Two Cl–O bonds are single and two are double, resulting in twelve electrons around chlorine.
Which statement most accurately compares structures I and II?
(a) Both structures are equally important resonance forms; resonance averages the bond orders so neither is preferred.
(b) Structure II is preferred because it reduces the overall magnitude of formal charges on the ion, giving chlorine a +1 formal charge and placing the −1 charge only on the singly bonded oxygens.
(c) Structure I is preferred because atoms beyond the second period must still obey the octet rule, so any structure with more than eight electrons on chlorine is forbidden.
(d) Structure I is preferred because it keeps the formal charge on chlorine at 0, whereas Structure II would give chlorine a positive formal charge.