Chapter 3, Problem 23P

Interpretation Introduction

Interpretation:

The number of normal modes of vibration are IR active for (a) ${\text{H}}_{\text{2}}\text{O}$, (b) ${\text{SiF}}_{\text{4}}$, (c) ${\text{PCl}}_{\text{3}}$, (d) ${\text{AlCl}}_{\text{3}}$, (e) ${\text{CS}}_2$, and (f) $\text{HCN}$ are to determined.

Concept Introduction:

Raman and infrared (IR) spectroscopies are branches of vibrational spectroscopy.

Vibrational spectroscopy is concerned with the observation and determination of number of the degrees of vibrational freedom.

The degrees of vibrational freedom depends on the number of atoms in molecule and shape of the molecule.

The number and nature of the symmetry elements of a given molecule are conveniently represented by its point groups and give rise to labels such as ${\text{D}}_{\text{3h}}$, ${\text{T}}_{\text{d}}$, $O_h$, ${\text{I}}_h$, ${\text{D}}_{\text{2d}}$, ${\text{C}}_{\text{2}}$, ${\text{C}}_{\text{3v}}$ etc.