When a molecule absorbs IR eletromagnetic energy, what are the vibrational modes affected?

Stretching vibration and bending vibration

Explanation:

1. Stretching vibration results in the variation of the bond length. There are two types of stretching vibration:

In asymmetric bending, bonds move in and out as a result of the vibration. In symmetric bending, bonds move such that the bond length either gets shorter or longer.

2. Bending vibration results in the variation of the bond angle.

These can be grouped into 4 types:

Rocking - It is that motion in which two atoms are in the motion like that of the motion of a pendulum of a clock. Scissoring - The motion of to atoms either away from each other or towards each other. Twisting - It is where the motion of the two atoms resembles that of the motion on a treadmill. Wagging - It is the motion in V - shape in the back and forth direction.