London dispersion

Science

Definition

London dispersion forces are the weakest type of intermolecular force, caused by temporary fluctuations in the electron cloud of an atom or molecule that create instantaneous dipoles. These forces exist between all molecules and atoms but are the only intermolecular force present in nonpolar substances.

Examples

  • Noble gases like argon can be liquefied at very low temperatures due to London dispersion forces
  • Larger halogens (Br₂, I₂) have higher boiling points than smaller ones (F₂, Cl₂) because stronger London dispersion forces arise from more electrons
  • Gecko feet stick to surfaces partly through London dispersion forces between their toe pads and the surface
Key Fact

Strength increases with molecular size (more electrons = larger, more polarizable electron cloud).

Related Terms

Dipole-dipole Hydrogen bonding Covalent bonds Phases of matter

Study This Concept

Practice London dispersion with free review games in these units:

AP Chemistry Unit 3: Intermolecular Forces