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.

vibration-tension Tension Vibration

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

vibration-stress-symmetrical Symmetrical stress vibration

vibration-asymmetric-tension 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.

vibration-flexion-scissors Scissor bending vibration.

vibration-flexion-roll Bending vibration, rocking

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

vibration-flexion-pitch Bending vibration, pitching

vibration-flexion-torsion Bending vibration, torsion

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