Telluride (Te2−): the tellurium(−II) ion and its compounds

Chemical properties

Telluride (Te2−) carries two extra electrons and is therefore a strong reducing agent; it can donate electrons to other species. It is the fully deprotonated form of the hydrogen telluride system: when a proton is added to Te2− it forms the monoanionic species HTe−, and further protonation under acidic conditions yields hydrogen telluride gas (H2Te). These relationships are often discussed together: see the telluride ion, telluride compounds, and examples such as sodium telluride and hydrogen telluride.

Occurrence and formation

In aqueous chemistry Te2− exists only in strongly alkaline media: under less basic conditions tellurium is progressively protonated to HTe− and eventually converted to H2Te in sufficiently acidic solutions. In nature, tellurium is most often recovered from telluride minerals where tellurium is bound with metals rather than occurring as a free Te2− ion, and such minerals are a chief source of elemental tellurium.

Uses and examples

Inorganic tellurides and organotellurium compounds have diverse roles. Simple salts like sodium telluride are reagents in laboratory synthesis. Many metal tellurides are important materials in industry: for example, some telluride-based ceramics and intermetallics are used in thermoelectric devices and semiconductors. Because telluride-containing minerals are the principal economic source of tellurium, extraction and refining of those ores supply the element for these applications. For context on reactivity, note that tellurides are classed among reducing agents in chemical literature reducing agents.

Distinctions and notable facts

Mineral tellurides frequently exhibit metallic or covalent bonding and are not simple ionic materials. The stepwise protonation sequence Te2− → HTe− → H2Te is important for understanding behavior in solution and during ore processing, and it explains why free Te2− is only present at very high alkalinity (very high pH). Telluride compounds are also the principal form in which tellurium is found geologically and commercially (tellurium sources).

Safety and handling

Hydrogen telluride (H2Te) is a volatile, unpleasant-smelling gas with toxic properties and must be handled with care; laboratory tellurides are typically handled under inert or basic conditions to avoid release of the gaseous hydride. For further technical details and compound-specific data consult specialized sources on H2Te and references for inorganic tellurides here.