SeO42

SeO4^2-, commonly called selenate, is the tetrahedral oxoanion of selenium in the +6 oxidation state. Its formula is SeO4^2-. Selenate forms salts such as Na2SeO4, K2SeO4, and (NH4)2SeO4, which are typically white and highly soluble in water. In aqueous solution, the Se–O bonds retain a tetrahedral geometry around selenium.

Occurrence and production: Selenate occurs naturally in oxidized selenium-bearing minerals and is a common selenium species in aerobic soils and groundwater, often forming by oxidation of elemental selenium or selenium-containing minerals. Industrially, selenate salts can be produced by neutralizing selenic acid (H2SeO4) with base or by oxidation of lower oxidation state selenium compounds to the +6 state.

Reactions and chemistry: SeO4^2- represents the highest common oxidation state of selenium in oxoanions and can be reduced to selenite SeO3^2- or to elemental selenium under reducing conditions. It forms complexes with various cations and can participate in the synthesis of organoselenium compounds.

Applications: Sodium and potassium selenates are used as selenium supplements in agriculture and animal feed, contributing to dietary selenium. They are also employed in some glass and pigment applications and as reagents in inorganic synthesis for introducing selenium(VI) into compounds.

Safety: Selenium compounds, including selenates, are toxic at elevated exposures. Handling requires appropriate safety precautions to avoid ingestion, inhalation, or dermal exposure, as chronic overexposure can cause selenosis.