It has both properties of metal and nonmetal. Tellurium belongs to chalcogen (oxygen family). Tellurium atomic number is 52 and atomic mass is about 127.60 g/mol. It has high melting point about 449.51 oC and boiling point is 988 oC. In molten form, tellurium is corrosive to copper, iron and stainless steel. Amorphous form exists in black brown powder, which is prepared by precipitating a solution of telluric acid. Crystalline tellurium looks silvery white and have a metallic luster. It has two allotropes: crystalline and amorphous. Tellurium is semimetallic element present in the oxygen group of the periodic table. The largest producers of tellurium are Canada, Japan and the United States. It is mostly found in the ores sylvanite (AgAuTe 4 Silver Gold Telluride), calaverite (AuTe 2 Gold Telluride) and krennerite (AuTe 2 Orthorhombic gold telluride). It is obtained as a by-product during the refinement of lead or copper. Like other metals such as copper, lead, silver or gold, it is often found in uncombined form but mostly present in mineral with gold. The high atomic number and the formation of halides caused it to be lost in the space as a gas during the hot nebular formation of the planet. Tellurium is present in about 1 part per billion in the Earth’s crust. Tellurium is not very common in the earth crust. In 1960, tellurium was widely used in steel alloys and thermoelectric applications. The word tellurium has been derived from Latin word ‘tellus’ that means ‘Earth’. In 1798, Martin Heinrich Klaproth confirmed the existence of that element and named that new element tellurium. He sent sample to Torbern Bergman in Uppsala, Sweden but he died. Officially, it was discovered by Franz Joseph Muller von Reichenstein in 1782. They called that element aurum paradoxum or metallum problematum, meaning problem metal. In 1700, scientist found a new element in various ores who had both metallic and non-metallic properties. Tellurium used as semiconductor and photosensitive material. It is semi-metallic in nature and present in the oxygen group of periodic table.
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