Tension vibration (stretching). Atoms held together by single, double, or triple bonds move toward and away in the direction of the bond, just as two masses attached to a spring oscillate.

Tension Vibration

There are two modes of tension vibration: symmetric and asymmetric.

Symmetrical stress vibration

Asymmetric stress vibration

Bending vibration . The atoms vibrate so that the angles vary, but the bond lengths do not. There are four modes of bending vibrations: scissoring, rocking, wagging, and twisting.

Scissor bending vibration.

Bending vibration, rocking

These two modes of vibration take place in the plane that contains the three atoms that participate in the vibration.

Bending vibration, pitching

Bending vibration, torsion

The pitch and torsion modes of vibration occur out of plane (Out of plane) and are usually represented by Oop.