Which force is responsible for the attraction between nonpolar molecules?

Dispersion forces, also known as London dispersion forces, are the primary intermolecular forces that account for the attraction between nonpolar molecules. These forces arise from temporary fluctuations in electron distribution within molecules, which create instantaneous dipoles. Even in nonpolar molecules, where there is no permanent dipole, these temporary dipoles can induce corresponding dipoles in neighboring molecules, resulting in a weak attraction.

As more electrons are present, the strength of dispersion forces can increase, leading to greater attractions between larger or more polarizable nonpolar molecules. This is why substances like noble gases or hydrocarbons, which are primarily nonpolar, can condense into liquids and solids at low temperatures; the dispersion forces, although weak compared to other types of intermolecular forces, still play a significant role in their physical properties.

In contrast, dipole-dipole forces, ionic bonds, and hydrogen bonding are associated with polar molecules or involve stronger interactions that do not apply to nonpolar substances. Thus, dispersion forces are indeed the appropriate explanation for the attraction between nonpolar molecules.