Consider the perchlorateanion.

(a) what is the central atom?
(b) how many lone pairs are around the central atom?
(c) what is the ideal angle between the chlorine-oxygen bonds?
(d) compared to the ideal angle, you would expect the actual angle between the chlorine-oxygen bonds to be

(a) Chlorine atom

(b) 0

(c) 109.5°

(d) about the same

Explanation:

Perchlorate is a negatively charged molecule that is composed of one carbon atom and four oxygen atoms. In this molecule, the central chlorine atom that is present in +7 oxidation state, is covalently bonded to four oxygen atoms.

Thus the number of bond pairs is 4 and the number of lone pairs on the central chlorine atom is 0.

So according to the VSEPR theory, perchlorate ion has a tetrahedral geometry. Therefore, the ideal bond angle for the perchlorate ion is 109.5°.

The actual bond angle of perchlorate is about the same as ideal bond angle. This is because the perchlorate is resonance stabilized and thus all the chlorine-oxygen bonds are equivalent.