expansion of solar cell industry in China. In 2022, the largest Te providers by volume were China (340 tonnes), Russia (80 t), Japan, (70 t), Canada (50 t), Uzbekistan (50 t), Sweden (40) and the United States (no official data). Compounds Tellurium belongs to the chalcogen (group 16) family of elements on the periodic table, which also includes oxygen, sulfur, selenium and polonium: Tellurium and selenium compounds are similar. Tellurium exhibits the oxidation states −2, +2, +4 and +6, with +4 being most common. Tellurides Reduction of Te metal produces the tellurides and polytellurides, Ten2−. The −2 oxidation state is exhibited in binary compounds with many metals, such as zinc telluride, , produced by heating tellurium with zinc. Decomposition of with hydrochloric acid yields hydrogen telluride (), a highly unstable analogue of the other chalcogen hydrides, , and : Halides The +2 oxidation state is exhibited by the dihalides, , and . The dihalides have not been obtained in pure form, although they are known decomposition products of the tetrahalides in organic solvents, and the derived tetrahalotellurates are well-characterized: where X is Cl, Br, or I. These anions are square planar in geometry. Polynuclear anionic species also exist, such as the dark brown , and the black . With fluorine Te forms the mixed-valence and . In the +6 oxidation state, the structural group occurs in a number of compounds such as , , , and . The square antiprismatic anion is also attested. The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (, and ) in the +4 state, and other lower halides (, , , and two forms of ). In the +4 oxidation state, halotellurate anions are known, such as and . Halotellurium cations are also attested, including , found in . Oxocompounds Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of in vacuum, disproportionating into tellurium dioxide, and elemental tellurium upon heating. Since then, however, existence in the solid phase is doubted and in dispute, although it is known as a vapor fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide. Tellurium dioxide is formed by heating tellurium in air, where it burns with a blue flame. Tellurium trioxide, β-, is obtained by thermal decomposition of . The other two forms of