Tellur

Tellur, or tellurium, is a chemical element with the symbol Te and atomic number 52. It is classified as a brittle, silvery-white metalloid in the chalcogen group. Tellurium occurs only in trace amounts in the Earth's crust and is mainly found in telluride minerals such as calaverite (gold telluride) and krennerite, and it is typically recovered as a byproduct of copper and other metal refining rather than from native ore.

Discovery and etymology: Tellurium was first described in 1782 by Franz-Joseph Müller von Reichenstein, but its recognition as a chemical element is credited to Martin Heinrich Klaproth in 1798, who named it from the Latin tellus, meaning earth.

Properties: Tellurium is a brittle semimetal with several allotropes. At room temperature it forms crystalline, metallic-looking solids and behaves as a semiconductor. It has a relatively high melting point of about 449.5°C and a boiling point near 988°C, with a density around 6.2 g/cm³. Its chemistry includes compounds such as TeO2 and TeO3, and it forms tellurides and organotellurium compounds.

Occurrence and production: Tellurium is a rare element, widely dispersed in the crust but concentrated in telluride minerals. Commercial production occurs mainly as a byproduct of copper refining, recovered from electrolytic anode slimes and other refining processes.

Uses: The principal modern applications of tellurium are in thermoelectric materials (often in compounds like bismuth telluride and antimony telluride for cooling and power generation) and in cadmium telluride (CdTe) thin-film solar cells. It is also used as an alloying agent to improve machinability in steel and copper and in various electronic and optical materials.

Safety: Tellurium and many of its compounds are toxic if ingested or inhaled. Exposure can cause adverse health effects, and tellurium compounds can produce a characteristic garlic-like odor on breath. Proper handling and containment are advised.