Mehrwertigen

Mehrwertigen is the declined form of the German adjective mehrwertig, used in chemistry to describe substances or species that can form more than one bond or have multiple reactive centers. The English equivalent is polyvalent or multivalent, and the term contrasts with monovalent (einwertig) and divalent (zweivalent) states.

In inorganic chemistry, mehrwertigkeit refers to the ability of elements to exist in different valence states or bonding configurations. For example, carbon is tetravalent, nitrogen is typically trivalent, and sulfur can range from divalent to hexavalent. Iron and other transition metals often display multiple oxidation states, illustrating the broader idea of variable valence in solids and solutions.

In ionic chemistry, mehrwertige Ionen denotes ions carrying more than one positive charge, such as calcium in Ca2+ or iron in Fe3+. Such ions exhibit higher charge densities and distinct chemical behavior compared with monovalent ions.

In organic and polymer chemistry, mehrwertige Verbindungen are molecules with two or more reactive groups, enabling crosslinking and the formation of extended networks. Examples include glycols with two hydroxyl groups and multifunctional crosslinkers used in polyurethanes and epoxies. These multi- or crosslinking functionalities are central to the properties of many polymers and biomaterials.

Limitations: The practical meaning of mehrwertigkeit depends on context, and the concept of valence evolves with advances in electronic structure theory, particularly for transition metals where oxidation state and covalency play important roles.

See also: Valence (Chemistry); Polyvalent; Monovalent; Divalent; Multivalent ligands.