Tellurate

In chemistry tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.

Tellurium oxyanions

Historically the name tellurate was only applied to oxyanions of tellurium with oxidation number +6, formally derived from telluric acid Te(OH)₆, and the name tellurite referred to oxyanions of tellurium with oxidation number +4, formally derived from tellurous acid (HO)₂TeO and these names are in common use. However tellurate and tellurite are often referred to as tellurate(VI) and tellurate(IV) respectively in line with IUPAC renaming recommendtaions. The metatellurate ion is TeO₄²⁻ and the orthotellurate ion is TeO₆⁶⁻. Other oxyanions include pentaoxotellurate, TeO₅⁴⁻, ditellurate, Te₂O₁₀⁸⁻ and polymeric anions with 6 coordinate tellurium such as (TeO₅⁴⁻)_n.

Metatellurates

The metatellurate ion TeO₄²⁻ is analogous to the sulfate ion, SO₄²⁻ and the selenate ion, SeO₄²⁻. Whereas many sulfates and selenates form isomorphous salts the tetrahedral metatellurate ion is only found in a few compounds such as the tetraethylammonium salt N(Et)₄TeO₄. Many compounds with a stoichiometry that suggests the presence of a metatellurate ion actually contain polymeric anions containing 6 coordinate tellurium(VI), for example sodium tellurate, Na₂TeO₄ which contains octahedral tellurium centers sharing edges.