London dispersion force is a weak intermolecular force between two atoms or molecules in close proximity to each other. The force is a quantum force generated by electron repulsion between the electron clouds of two atoms or molecules as they approach each other. The London dispersion force is the weakest of the van der Waals forces and is the force that causes nonpolar atoms or molecules to condense into liquids or solids as temperature is lowered. Even though it is weak, of the three van der Waals forces (orientation, induction, dispersion), the dispersion forces are usually dominant. The exception is for small, readily polarized molecules (e.g., water). The force gets its name because Fritz London first explained how noble gas atoms could be attracted to each other in 1930. His explanation was based on second-order perturbation theory. Also Known As: London forces, LDF, dispersion forces, instantaneous dipole forces, induced dipole forces. London dispersion forces may sometimes be loosely referred to as van der Waals forces. When you think of electrons around an atom, you probably picture tiny moving dots, spaced equally around the atomic nucleus. However, electrons are always in motion, and sometimes there are more on one side of an atom than on the other. This happens around any atom, but it’s more pronounced in compounds because electrons feel the attractive pull of the protons of neighboring atoms. The electrons from two atoms can be arranged such that they produce temporary (nstantaneous) electric dipoles. Even though the polarization is temporary, it’s enough to affect the way atoms and molecules interact with each other.