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Selenium is a nutrient that is naturally present in many foods, added to others and is also available as a dietary supplement in pill, powder and liquid form, explains Perri Halperin, a ...
Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells.
Selenium is a soft (MH 2.0) and brittle semi-metallic element. It is commonly regarded as a nonmetal, but is sometimes considered a metalloid or even a heavy metal . Selenium has a hexagonal polyatomic (CN 2) crystalline structure.
The chemistry of selenium is largely covalent in nature, noting it can form ionic selenides with highly electropositive metals. The common oxide of selenium (SeO 3) is strongly acidic. Tellurium. Tellurium is a silvery-white, moderately reactive, [8] shiny solid, that has a density of 6.24 g/cm 3 and is soft (MH 2.25) and brittle. It is the ...
The chemical elements can be broadly divided into metals, metalloids, and nonmetals according to their shared physical and chemical properties.All elemental metals have a shiny appearance (at least when freshly polished); are good conductors of heat and electricity; form alloys with other metallic elements; and have at least one basic oxide.
Selenium is commonly described as a metalloid in the environmental chemistry literature. [450] It moves through the aquatic environment similarly to arsenic and antimony; [ 451 ] its water-soluble salts, in higher concentrations, have a similar toxicological profile to that of arsenic.
This results in six or seven sets of nonmetals, depending on the treatment of boron, which in some cases is regarded as a metalloid. The size of the group 14 set, and the sets of nonmetal pnictogens, chalcogens, and halogens will vary depending on how silicon, germanium, arsenic, antimony, selenium, tellurium, and astatine are treated.
[n 5] One or more of carbon, aluminium, phosphorus, selenium, tin or bismuth, these being periodic table neighbours of the elements commonly classified as metalloids, are sometimes recognised as metalloids. [n 6] Selenium, in particular, is commonly designated as a metalloid in environmental chemistry [n 7] on account of similarities in its ...