Chapter 3, Problem 28P

${\text{Al}}_{\text{2}}{\text{Cl}}_{\text{6}}$ belongs to the ${\text{D}}_{\text{2h}}$ point group:

1. How many degrees of vibrational freedom does ${\text{Al}}_{\text{2}}{\text{Cl}}_{\text{6}}$ possess?

2. Use the ${\text{D}}_{\text{2h}}$ character table in appendix 3 to determine the symmetries of the IR active stretching modes of vibration.