What are London Dispersion forces primarily caused by?

London Dispersion forces arise primarily from the constant motion of electrons within atoms and molecules, leading to the formation of temporary, or instantaneous, dipoles. These dipoles occur when the distribution of electrons around an atom or molecule becomes uneven at any given moment, creating a momentary positive and negative pole. As these instantaneous dipoles form, they can induce dipoles in neighboring atoms or molecules, leading to an attractive force between them.

This phenomenon is not restricted to any specific type of molecule and can occur in nonpolar molecules as well, making London Dispersion forces significant even in substances that do not have permanent dipoles. The strength of these forces generally increases with the size of the molecule, as larger atoms have more electrons that can contribute to the formation of dipoles. Understanding these forces is crucial in explaining various physical properties of substances, such as boiling points and melting points.