Salt (chemistry)

In chemistry, a salt or ionic compound is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a neutral compound with no net electric charge. The constituent ions are held together by electrostatic forces termed ionic bonds.

The component ions in a salt can be either inorganic, such as chloride (Cl⁻), or organic, such as acetate (CH
₃COO⁻
). Each ion can be either monatomic (termed simple ion), such as fluoride (F⁻), and sodium (Na⁺) and chloride (Cl⁻) in sodium chloride, or polyatomic, such as sulfate (SO²⁻
₄), and ammonium (NH⁺
₄) and carbonate (CO²⁻
₃) ions in ammonium carbonate. Salt containing basic ions hydroxide (OH⁻) or oxide (O²⁻) are classified as bases, for example sodium hydroxide.

Individual ions within a salt usually have multiple near neighbours, so are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures when solid.

Salts composed of small ions typically have high melting and boiling points, and are hard and brittle. As solids they are almost always electrically insulating, but when melted or dissolved they become highly conductive, because the ions become mobile. Some salts have large cations, large anions, or both. In terms of their properties, such species often are more similar to organic compounds.