Dispersion Forces

Dispersion forces arise when two molecules that have neither a net charge nor a permanent dipole moment come into very close contact. When this happens, the molecules synchronize their charge fluctuations so as to give a net attractive force. This can be thought of as a simultaneous, mutual dipole induction. This attractive energy varies as the inverse sixth power of the distance, so dispersion forces are significant only at very short range (See Figure 2.5).

See also: Induced Dipoles, Permanent Dipole Moment