zweivalenten

Zweivalenten is a term used in German-language chemistry to denote species that have a valence of two, i.e., that can form two chemical bonds or carry a two-unit oxidation state. In modern English-language chemistry the corresponding term is divalent or two-valent. Valence refers to the bonding capacity of an atom or ion, whereas oxidation state describes the formal charge assigned in a compound; a two-valent species may carry a +2 or -2 charge, or form two covalent bonds without a permanent ionic charge.

Common examples of zweivalenten include divalent metal cations such as calcium(II) (Ca2+), magnesium(II) (Mg2+), iron(II) (Fe2+), and zinc(II) (Zn2+). Non-metal elements such as oxygen are often described as divalent in many compounds, for instance oxide O2− in oxides, where the element forms bonds or bears a two-unit charge. In coordination chemistry and solid-state chemistry, zweivalenten centers can bridge two ligands or two metal centers, influencing structure and properties.

The term is largely historical or regional, with modern terminology preferring divalent. In German texts you may encounter 'Zweivalente' or 'Zweivalenten' as adjectives or nouns referring to such two-valence species. See also monovalent, trivalent for related concepts.