molecules create small temporary dipoles, with extremely short lifetimes. These dipoles
in turn attract or repel electrons in adjacent molecules, setting up dipoles in them as
well. The result is an overall attraction among molecules. These attractive forces are
called London or dispersion forces, and make liquefaction of the noble gases and nonpolar
molecules such as hydrogen, nitrogen, and carbon dioxide possible. As a general
rule, London forces are more important when there are more electrons in a molecule,
because the attraction of the nuclei is shielded by inner electrons and the electron cloud
is more polarizable.