Editing Selenium (section)

{{About|the chemical element|the software testing framework|Selenium (software)}}
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{{Infobox selenium}}

'''Selenium''' is a [[chemical element]]; it has [[symbol (chemistry)|symbol]] '''Se''' and [[atomic number]] 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure [[ore]] compounds in [[Earth's crust]]. Selenium ({{lang|grc|σελήνη}} {{gloss|moon}}) was discovered in 1817 by {{lang|sv|italics=unset|[[Jöns Jacob Berzelius]]}}, who noted the similarity of the new element to the previously discovered [[tellurium]] (named for the Earth).

Selenium is found in [[:Category:Sulfide minerals|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 [[pigment]]s. Selenium is a [[semiconductor]] and is used in [[photocell]]s. Applications in [[electronics]], once important, have been mostly replaced with [[silicon]] semiconductor devices. Selenium is still used in a few types of [[Direct current|DC power]] [[surge protector]]s and one type of [[Fluorescence|fluorescent]] [[quantum dot]].

Although [[essential trace element|trace]] amounts of selenium are necessary for [[Cell (biology)#Cellular processes|cellular function]] in many animals, including humans, both elemental selenium and (especially) selenium [[salt (chemistry)|salts]] are toxic in even small doses, causing [[Selenium#Toxicity|selenosis]].<ref>{{Cite journal |last1=Fernández-Bautista |first1=Tamara |last2=Gómez-Gómez |first2=Beatriz |last3=Palacín-García |first3=Roberto |last4=Gracia-Lor |first4=Emma |last5=Pérez-Corona |first5=Teresa |last6=Madrid |first6=Yolanda |date=2022-01-15 |title=Analysis of Se and Hg biomolecules distribution and Se speciation in poorly studied protein fractions of muscle tissues of highly consumed fishes by SEC-UV-ICP-MS and HPLC-ESI-MS/MS |url=https://www.sciencedirect.com/science/article/pii/S0039914021008444 |journal=Talanta |volume=237 |pages=122922 |doi=10.1016/j.talanta.2021.122922 |pmid=34736659 |s2cid=243761320 |issn=0039-9140}}</ref> Symptoms include (in decreasing order of frequency): diarrhea, fatigue, hair loss, joint pain, nail brittleness or discoloration, nausea, headache, tingling, vomiting, and fever.<ref name="pmid20142570">{{cite journal | vauthors=MacFarquhar JK, Broussard, DOL, Jones TF | title=Acute selenium toxicity associated with a dietary supplement | journal=[[JAMA Internal Medicine|Archives of Internal Medicine]] | volume=178 | issue=3 | pages=256–261 | year=2010 |  doi = 10.1001/archinternmed.2009.495 | pmc=3225252 | doi-access=free | pmid=20142570 }}</ref>

Selenium is listed as an ingredient in many multivitamins and other dietary supplements, as well as in [[infant formula]], and is a component of the antioxidant enzymes [[glutathione peroxidase]] and [[thioredoxin reductase]] (which indirectly reduce certain [[Redox|oxidized]] molecules in animals and some plants) as well as in three [[deiodinase]] enzymes. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts and others apparently not requiring any.<ref name="Ruyle">{{cite web |url=https://cals.arizona.edu/arec/pubs/rmg/1%20rangelandmanagement/2%20poisonousplants93.pdf |title=Poisonous Plants on Arizona Rangelands |first=George |last=Ruyle |access-date=2009-01-05 |publisher=The University of Arizona |url-status=dead |archive-url=https://web.archive.org/web/20040715194026/http://cals.arizona.edu/AREC/pubs/rmg/1%20rangelandmanagement/2%20poisonousplants93.pdf |archive-date=2004-07-15 |df=dmy-all}}</ref>