Editing Selenium (section)

===Metal selenides===
[[File:Polyselenide.svg|thumb|Structures of two polyselenide anions<ref>{{Greenwood&Earnshaw2nd|page=763-765}}</ref>]]
Analogous to the behavior of other chalcogens, selenium forms [[hydrogen selenide]], H<sub>2</sub>Se. It is a strongly [[wikt:odiferous|odiferous]], toxic, and colorless gas. It is more acidic than H<sub>2</sub>S. In solution it ionizes to HSe<sup>−</sup>. The selenide dianion Se<sup>2−</sup> forms a variety of compounds, including the minerals from which selenium is obtained commercially. Illustrative selenides include [[mercury selenide]] (HgSe), [[lead selenide]] (PbSe), [[zinc selenide]] (ZnSe), and [[copper indium gallium diselenide]] (Cu(Ga,In)Se<sub>2</sub>). These materials are [[semiconductor]]s. With highly electropositive metals, such as [[aluminium]], these selenides are prone to hydrolysis, which may be described by this idealized equation:<ref name="house2008" />

:{{chem2 | Al2Se3 + 6 H2O -> 2 Al(OH)3 + 3 H2Se }}

Alkali metal selenides react with selenium to form polyselenides, {{chem|Se|n|2-}}, which exist as chains and rings.