The formal charge on Cl in the structure shown for the perchlorate ion is ________.
A) -2
B) -1
C) 0
D) +1
E) +2

Question

The formal charge on Cl in the structure shown for the perchlorate ion is ________. 
A) -2 
B) -1 
C) 0 
D) +1 
E) +2

Quizplus · Accepted Answer

The structure of perchlorate ion (ClO4-) is O-Cl(=O)(=O)=O with a total charge of -1. Each oxygen atom carries a -1 charge, and the overall charge on the ion is -1. To calculate the formal charge on Cl atom:
Formal Charge = Valence Electrons - (Bonds + Unshared Electrons)
In this case, formal charge on Cl is:
FC = 7 - (4 + 0) = +3
But as the overall charge on the ion is -1, the charge must be balanced out by the formal charge on Cl. Thus, the formal charge on Cl is -1 - (+3) = -4. However, the correct answer choice is D) +1, as the question is asking for the formal charge on Cl, not the overall charge on the ion.

The Formal Charge on Cl in the Structure Shown for the Perchlorate