Bond angle

[manasa933]

According the solutions manual, the bond angle of ClO2+ is slightly less than 120 degrees and its electron arrangement is trigonal planar.

But since there are two lone pairs on the chlorine atom, shouldn't it be tetrahedral and slightly less than 90 degrees?

[Austin Ho 1E]

There is only 1 lone pair on the Chlorine atom. In ClO2+, there are 7+12-1 electrons, or 18 electrons total. 2x6 electrons go on the oxygens, plus 2x2 electrons that bond the Oxygens to the Chlorine atom. That leaves us with 2 more electrons, or 1 lone pair on the Cl atom. Thus, since there are 3 regions of electron density around the Chlorine atom, the parent shape is trigonal planar and thus the bond angles with oxygen are less than 120.

What you said would be true if it was ClO2-, then there would be 20 electrons total, with 2 lone pairs on Cl.

Hope this helps!