Which type of intermolecular force is present in nonpolar molecules and arises from temporary dipoles?

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

Answer: (A)

Nonpolar molecules lack permanent dipoles, so the attractions between them come from temporary fluctuations in electron distribution. As electrons move, a momentary region of negative charge can appear on one side of a molecule, creating an instantaneous dipole. This dipole can induce a similar dipole in a neighboring molecule, pulling them together slightly. That whole, fleeting attraction is called London dispersion forces. They are present in all substances but dominate in nonpolar ones, and their strength grows with the molecule’s size and polarizability (more electrons and a larger surface area mean easier distortion of the electron cloud). Hydrogen bonding and dipole-dipole interactions rely on permanent dipoles or specific attachments like N–H, O–H, or F–H bonds, so they don’t apply to nonpolar molecules. Electrostatic interactions cover ionic or charged species, which isn’t the situation here.