Intermolecular force

An attractive or repulsive interaction between molecules, distinct from the chemical bonds holding atoms together within a molecule. These forces influence how substances condense, dissolve, and behave in mixtures.

London dispersion force: An attraction between particles caused by instantaneous fluctuations in electron distribution that induce correlated dipoles. Temporary dipoles create this universal attraction, even between nonpolar molecules.
Boiling point: The temperature at which a liquid's vapor pressure equals the pressure surrounding it. Stronger attractions generally require more heat for molecules to escape into vapor.
Electric dipole moment: A vector measure of the separation of positive and negative charge in a system. Permanent and induced dipoles underlie several common intermolecular attractions.
Covalent bond: A chemical bond formed when atoms share one or more pairs of electrons. It holds atoms together within molecules rather than describing attraction between separate molecules.
Dipole–dipole interaction: An electrostatic interaction between molecules with permanent electric dipole moments. Molecular orientation determines the attraction between permanent dipoles.
Vapor pressure: The pressure exerted by a vapor in equilibrium with its condensed phase at a given temperature. Molecular attractions affect how readily molecules leave a liquid's surface.
Polar molecule: A molecule with a nonzero permanent electric dipole moment. Its uneven charge distribution enables orientation-dependent electrostatic interactions.
Ionic bond: An electrostatic attraction between oppositely charged ions in an ionic substance. Its extended ionic lattice differs from forces between discrete molecules.
Hydrogen bond: A directional attraction involving hydrogen bonded to an electronegative atom and another electron-rich atom or group. This unusually strong, directional interaction is a special case of intermolecular attraction.
Viscosity: A measure of a fluid's resistance to flow. Cohesive molecular attractions can impede the motion of neighboring molecules.

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