Overview

Selenide commonly refers to the inorganic anion Se2− and to materials that contain this species. The simple definition and basic properties are summarized in introductory sources such as the selenide ion entry. Selenides are the selenium analogues of sulfides and share many chemical behaviors, but with distinct reactivity and physical properties.

Chemical behavior and species

In aqueous chemistry the true selenide ion is stable only under strongly basic conditions; in moderately basic solutions the conjugate form, the hydroselenide anion HSe−, predominates and is discussed at hydroselenide. Under acidic conditions protonation produces hydrogen selenide (H2Se), a volatile gas treated in more detail at hydrogen selenide. Selenides act as reducing agents and, when pure, are generally stronger reducing agents than their sulfur analogues — a point often noted in summaries of reducing species like reducing agents. The redox and acid–base equilibria determine which selenium species are present in a given environment.

Common compounds and structure

Metal selenides include simple ionic salts such as sodium selenide as well as more complex semiconductor phases. Examples include:

  • Binary metal selenides (e.g., copper, cadmium, iron selenides)
  • Compound semiconductors such as CuInSe2 and CdSe
  • Mixed sulfide–selenide minerals commonly found together in ore deposits

Occurrence, history and preparation

Selenide minerals supply much of the world's selenium and are often associated with sulfide ores. Historically selenium was identified as an element in the early 19th century and its mineralogy and compounds were characterized as analytical chemistry developed. In the laboratory selenide species are generated by deprotonation of hydrogen selenide or by direct combination of selenium with reactive metals; their stability depends strongly on pH and redox conditions, as summarized in basic references such as the discussion of basic conditions at basic conditions.

Uses and significance

Selenide compounds are important in materials science: CdSe and related compounds are used in optoelectronics and quantum dots; CuInSe2 and related chalcogenides are relevant to thin-film photovoltaics and thermoelectric materials. Metal selenides also appear in research on superconductivity and electronic materials (for example iron selenide phases). In environmental and biological contexts selenide provides a source of selenium for biosynthetic pathways, but its chemistry in soils and waters is governed by pH and redox transformations.

Safety and distinguishing features

Hydrogen selenide (H2Se) is a toxic, flammable gas with a characteristic odor, so handling of acidified selenide solutions requires proper ventilation and controls. Compared with sulfides, selenides tend to be less common in the crust but show stronger reducing behavior and different optical and electronic properties, which explains their distinct technological roles.

Further reading and technical details can be found in specialized inorganic chemistry texts and material science reviews; introductory links include entries for the selenide ion, reducing agents, basic conditions, hydroselenide and hydrogen selenide.