Van der Waals force
A van der Waals force is an interaction between atoms, molecules or parts of molecules that is distinct from chemical bond formation and from the electrostatic interactions of ions. The term includes attractions involving permanent and induced electric dipoles, as well as London dispersion forces. In broader usage it can include nonspecific short-range repulsion as well as attraction.[1]
Types of interaction
A permanent dipole arises when a molecule has an uneven distribution of electric charge. Two polar molecules can attract one another through their dipoles. A permanent dipole can also distort the electron distribution of a neighbouring particle, inducing a dipole there. IUPAC distinguishes these dipole–dipole and dipole-induced-dipole interactions from the instantaneous induced-dipole interactions associated with dispersion.[1]
Dispersion interactions occur even between nonpolar particles. Fluctuations in the electron distribution produce temporary dipoles whose effects are correlated with neighbouring particles. The ease with which an electron cloud can be distorted is its polarizability. More polarizable particles generally experience stronger dispersion attractions.[2]
Effects on materials
Intermolecular attractions help explain why gases can condense and why substances have different boiling points. They are normally weaker than the covalent bonds within a small molecule, so vaporising a molecular liquid need not break the molecules themselves. Molecular shape matters as well as size: shapes that permit greater contact can produce stronger overall attractions.[2]
The expression van der Waals force is used with different breadth in different discussions. A distinction between a particular contribution, such as dispersion, and the total interaction is therefore necessary when comparing descriptions. It does not designate an additional chemical bond that must be present alongside every covalent or ionic bond.[1]
References
- ↑ 1.0 1.1 1.2 International Union of Pure and Applied Chemistry. Van der Waals forces. Gold Book, 5th edition, 2025. doi:10.1351/goldbook.V06597.
- ↑ 2.0 2.1 OpenStax. Intermolecular Forces. Chemistry: Atoms First 2e.
Attribution
Adapted with reference to English Wikipedia, revision 1371351752 (contributors and history), under CC BY-SA 4.0. The prose has been rewritten and checked against the cited sources; changes have been made.