Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. It is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme rarity in the Earth’s crust, comparable to that of platinum, It is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth, and partly to tellurium’s low affinity for oxygen, which causes it to bind preferentially to other chalcophiles in dense minerals that sink into the core.
The element tellurium was isolated before it was actually known to be an elemental species. About 1782 Franz Joseph Muller von Reichenstein, an Austrian mineralogist, worked with an ore referred to as German gold. From this ore he obtained a material that defied his attempts at analysis and was called by him metallum problematicum.
In 1798 Martin Heinrich Klaproth confirmed Muller’s observations and established the elemental nature of the substance. He named the element after man’s “heavenly body” Tellus, or Earth. In humans, tellurium is partly metabolized into dimethyl telluride, (CH3)2Te, a gas with a garlic-like odor exhaled in the breath of victims of tellurium exposure or poisoning.
Characteristics of Tellurium
- It has two allotropes, crystalline and amorphous. When crystalline, It is silvery-white with a metallic luster. It is a brittle and easily pulverized metalloid.
- It is a semiconductor that shows a greater electrical conductivity in certain directions depending on atomic alignment; the conductivity increases slightly when exposed to light (photoconductivity).
- When molten, tellurium is corrosive to copper, iron, and stainless steel. Of the nnknchalcogens (oxygen-family elements), tellurium has the highest melting and boiling points, at 722.66 K (841.12 °F) and 1,261 K (1,810 °F), respectively.
- It has no biological function, although fungi can use it in place of sulfur and selenium in amino acids such as tellurocysteine and telluromethionine.