What forces arise from instantaneous dipoles caused by fluctuations in electron distribution?

• A. London dispersion forces
• B. Dipole-dipole interactions
• C. Hydrogen bonding
• D. Electrostatic interactions

Answer: (A)

Fluctuations in electron distribution create temporary, or instantaneous, dipoles. In any molecule, the electron cloud can momentarily shift so one side becomes slightly negative and the other slightly positive. This fleeting dipole can induce a similar dipole in a neighboring molecule, and the interaction between these induced dipoles attracts the molecules together. These London dispersion forces are the universal, weak yet important, intermolecular attractions that arise from such instantaneous dipoles, and they increase with molecular size and polarizability because larger, more easily distorted electron clouds produce stronger fluctuations.

The other options describe different types of interactions: dipole-dipole interactions come from permanent dipoles, hydrogen bonding requires specific donors and acceptors involving hydrogen, and electrostatic interactions is a broad term that doesn’t specify the transient nature of these fluctuations.