Which type of interaction is considered the most dominant van der Waals interaction?

The most dominant van der Waals interaction is London dispersion interactions. These interactions arise from the temporary fluctuations in electron density within atoms and molecules, leading to momentary dipoles. Even in nonpolar molecules, where there are no permanent dipoles, these instantaneous dipoles can induce dipoles in neighboring molecules, resulting in attractive forces.

London dispersion interactions are significant in all types of matter, regardless of whether the molecules are polar or nonpolar, and become particularly important in large molecules where the electron cloud can be more easily distorted. Their strength increases with the size and polarizability of the atoms or molecules involved, which is why they tend to dominate in condensed phases like liquids and solids.

Other types of interactions, such as permanent dipole interactions and hydrogen bonding, are important but are generally stronger than London dispersion interactions only in specific contexts. Permanent dipole interactions depend on the presence of permanent dipoles in the molecules, while hydrogen bonding is a specific case of dipole-dipole interaction involving hydrogen atoms bonded to highly electronegative atoms like oxygen or nitrogen. However, hydrogen bonds and permanent dipole interactions do not occur in all substances, making London dispersion interactions the most universally applicable and dominant type of van der Waals interaction.