tellurous

Tellurous is an adjective relating to tellurium, especially to compounds in which tellurium is in the +4 oxidation state. The term is used in inorganic chemistry to describe Te(IV) species and their chemistry, analogous to how the word sulfurous relates to sulfur in the +4 state.

In practice, tellurous compounds include the tellurite family, such as the tellurate TeO3^2− anion, and salts of this anion (for example, sodium tellurite Na2TeO3). The conjugate acid of tellurite is sometimes described as tellurous acid, H2TeO3, though such acids are often difficult to isolate and exist mainly in aqueous solution as hydrolyzed species.

Another common tellurous compound is tellurium(IV) oxide, TeO2, which represents tellurium in the +4 oxidation state in a simple oxide form. Tellurous species may also refer to other Te(IV) derivatives and intermediates encountered in redox chemistry or materials science.

Modern chemical nomenclature tends to favor explicit oxidation-state designations (such as tellurium(IV) oxide) or the common names tellurite and related salts, with the adjective tellurous appearing more often in older literature or as a descriptive label rather than a formal name. The related term telluric denotes compounds involving tellurium in higher oxidation states (notably Te(VI) in tellurates).

See also: tellurium, tellurite, tellurate, tellurium(IV) oxide.