What is Selenium atom?

     

Selenium is a chemical element with the symbol Se and atomic number 34.  It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and  below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.  It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust.  Selenium-from Ancient Greek "Moon"- was discovered in 1817 by Jons Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium.  

     Selenium is found in metal sulfide ores, where it partially replaces the sulfur.  Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production.  Minerals that are pure selenide or selenate compounds are known but rare.  The chief commercial uses for selenium today are glasssmaking and pigments.  Selenium is a semiconductor and is used in photocells.  Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices.  Selenium is still used in a few type of DC power surge protectors and one type of fluorescent quantum dot.  

     Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals.  Selenium is an ingredient in manu multivitamins and other dietary supplements, including infant formula.  It is a component of the antixidant enzymes glutathione peroxidase and thioredoxin reductase.  It is also found in three deiodinase enzymes, which convert one thyroid hormone to another.  Selenium requirement in plants differ by species, with some plants requiring relatively large amounts and other apparently requiring none.