tellurate

Tellurate refers to the oxoanions of tellurium in the +6 oxidation state, with the principal ion TeO4^2-. It forms salts collectively known as tellurates and is the higher-oxidation‑state analogue of tellurite (TeO3^2-, Te in +4). The common informally named orthotellurate ion TeO4^2- is derived from orthotelluric acid, H6TeO6.

Structure and properties: The tellurate anion is typically described as tetrahedrally coordinated, with four oxide ligands around a central tellurium atom carrying an overall −2 charge. In solid and solution forms, tellurates are usually colorless. They are most stable in basic or neutral media; under strongly acidic conditions they may be converted to telluric acid–related species.

Preparation and occurrence: Tellurate species can be produced by oxidation of tellurite under appropriate conditions or by oxidation of elemental tellurium in the presence of base. They also arise by deprotonation of orthotelluric acid. Common laboratory examples of tellurate salts include sodium tellurate (Na2TeO4) and potassium tellurate (K2TeO4).

Reactions and applications: Tellurate can be reduced to tellurite or to elemental tellurium under suitable redox conditions. In inorganic synthesis and analytical chemistry, tellurate salts serve as reagents and intermediates, and they feature in studies of Te chemistry and oxide chemistry.

See also: Tellurite, Orthotelluric acid, Sulfate, Selenate.