Why are London dispersion forces weak?

• London dispersion forces (LDF, also known as dispersion forces,

• London forces are a type of force acting between atoms and molecules. They are part of the van der Waals forces. The LDF is named after the German-American physicist Fritz London.

The LDF is a weak intermolecular force arising from quantum-induced instantaneous polarization multipoles in molecules. They can therefore act between molecules without permanent multipole moments.

London forces are exhibited by nonpolar molecules because of the correlated movements of the electrons in interacting molecules. Because the electrons in adjacent molecules "flee" as they repel each other, electron density in a molecule becomes redistributed in proximity to another molecule.

This is frequently described as the formation of instantaneous dipoles that attract each other. London forces are present between all chemical groups, and usually represent the main part of the total interaction force in condensed matter, even though they are generally weaker than ionic bonds and hydrogen bonds.

Check this to get more information about secondary interactions.