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Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals.
A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth.
A metalloid is an element that possesses a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals, and which is therefore hard to classify as either a metal or a nonmetal. This is a generic definition that draws on metalloid attributes consistently cited in the literature.
The elements commonly classified as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. [n 4] The status of polonium and astatine is not settled. Most authors recognise one or the other, or both, as metalloids; Herman, Hoffmann and Ashcroft, on the basis of relativistic modelling, predict astatine will be a monatomic metal.
The only metal having an ionisation energy higher than some nonmetals (sulfur and selenium) is mercury. [citation needed] Mercury and its compounds have a reputation for toxicity but on a scale of 1 to 10, dimethylmercury ((CH 3) 2 Hg) (abbr. DMM), a volatile colourless liquid, has been described as a 15. It is so dangerous that scientists have ...
Tellurium is a soft (MH 2.25) and brittle semi-metallic element. It is commonly regarded as a metalloid, or by some authors either as a metal or a non-metal. Tellurium has a polyatomic (CN 2) hexagonal crystalline structure. It is a semiconductor with a band gap of 0.32 to 0.38 eV.
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Oxygen, sulfur, and selenium are nonmetals, and tellurium is a metalloid, meaning that its chemical properties are between those of a metal and those of a nonmetal. [7] It is not certain whether polonium is a metal or a metalloid. Some sources refer to polonium as a metalloid, [2] [27] although it has some metallic properties.