Answer:
London dispersion force
Explanation:
London dispersion force (Instantaneous dipole-induced dipole interaction) is the weakest intermolecular force. It can occur in atoms or molecules (e.g. Helium atom) which have no permanent dipole, instantaneous dipoles will arise as a result of a momentary imbalance in electron distribution. This interaction only lasts for a very short time (i.e. a fraction of a microsecond).
