Editing Rare-earth element (section)

{{short description|Any of the fifteen lanthanides plus scandium and yttrium}}
{{Periodic table (micro)|title=Rare-earth elements<br/>in the periodic table|mark=Sc,Y,La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu}}
{{Use mdy dates|date=September 2020}}
{{Multiple image
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|image1=RareEarthOreUSGOV.jpg
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|caption1=[[Rare-earth mineral|Rare-earth ore]] ''(shown with a 19&nbsp;mm diameter [[United States penny|US 1&nbsp;cent]] coin for size comparison)''
|caption2=Refined rare-earth oxides are heavy, gritty powders usually brown or black, but can be lighter colors as shown here.{{longitem |''Legend:''<br />[[gadolinium]]{{·}}[[praseodymium]]{{·}}[[cerium]]<br />[[samarium]]{{·}}[[lanthanum]]<br />
[[neodymium]]|style=text-align: center; font-size: 0.9em;padding-top: 6px;}}
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The '''rare-earth elements''' ('''REE'''), also called the '''rare-earth metals''' or '''rare earths''', and sometimes the [[lanthanide]]s or lanthanoids (although [[scandium]] and [[yttrium]], which do not belong to this series, are usually included as rare earths),<ref>The 1985 [[International Union of Pure and Applied Chemistry]] "Red Book" (p.&nbsp;45) recommends that ''lanthanoid'' is used rather than ''lanthanide''. The ending "-ide" normally indicates a negative ion. However, owing to wide current usage, "lanthanide" is still allowed and is roughly analogous to rare-earth element.<br />{{RedBook2005|page=51}}</ref> are a set of 17 nearly indistinguishable lustrous silvery-white soft [[heavy metals]]. Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes.
The term "rare-earth" is a [[misnomer]] because they are not actually scarce, but historically it took a long time to isolate these elements.<ref>{{Cite news |date=2014-03-23 |title=Rare earths: Neither rare, nor earths |language=en-GB |work=BBC News |url=https://www.bbc.com/news/magazine-26687605 |access-date=2023-04-19}}</ref><ref>{{Cite web |last=Lee |first=Jordy |title=Rare Earths Explained |url=https://www.milkenreview.org/articles/rare-earths-explained |access-date=2023-04-19 |website=Milken Institute Review |language=en-US}}</ref>
They are relatively plentiful in the entire [[Earth's crust]] ([[cerium]] being the [[abundance of elements in Earth's crust|25th-most-abundant element]] at 68 parts per million, more abundant than [[copper]]), but in practice they are spread thinly as trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore at great expense; thus the name "rare" earths.

Scandium and yttrium are considered rare-earth elements because they tend to occur in the same [[ore]] deposits as the lanthanides and exhibit similar chemical properties, but have different electrical and [[magnetic properties]].<ref name="ASella2016"/><ref>{{cite book |title=The Elements |author=T Gray |publisher=Black Dog & Leventhal |year=2007 |pages=118–122 |chapter=Lanthanum and Cerium}}</ref> 

These metals tarnish slowly in air at room temperature and react slowly with cold water to form hydroxides, liberating hydrogen. They react with steam to form oxides and ignite spontaneously at a temperature of {{cvt|400|C|F}}. These elements and their compounds have no biological function other than in several specialized enzymes, such as in [[Lanthanide-dependent methanol dehydrogenase|lanthanide-dependent methanol dehydrogenases]] in bacteria.<ref>{{cite journal |last1=Huang |first1=Jing |last2=Yu |first2=Zheng |last3=Chistoserdova |first3=Ludmila |title=Lanthanide-Dependent Methanol Dehydrogenases of XoxF4 and XoxF5 Clades Are Differentially Distributed Among Methylotrophic Bacteria and They Reveal Different Biochemical Properties |journal=Frontiers in Microbiology |date=26 June 2018 |volume=9 |page=1366 |doi=10.3389/fmicb.2018.01366 |pmid=29997591 |pmc=6028718 |doi-access=free}}</ref> The water-soluble compounds are mildly to moderately toxic, but the insoluble ones are not.<ref>{{cite journal |last1=Malhotra |first1=Nemi |last2=Hsu |first2=Hua-Shu |last3=Liang |first3=Sung-Tzu |last4=Roldan |first4=Marri Jmelou M. |last5=Lee |first5=Jiann-Shing |last6=Ger |first6=Tzong-Rong |last7=Hsiao |first7=Chung-Der |date=2020-09-16 |title=An Updated Review of Toxicity Effect of the Rare Earth Elements (REEs) on Aquatic Organisms |journal=Animals |language=en |volume=10 |issue=9 |page=1663 |doi=10.3390/ani10091663 |issn=2076-2615 |pmc=552131 |pmid=32947815 |doi-access=free}}</ref> All isotopes of [[promethium]] are radioactive, and it does not occur naturally in the earth's crust, except for a trace amount generated by [[spontaneous fission]] of [[uranium-238]]. They are often found in [[mineral]]s with [[thorium]], and less commonly [[uranium]].

Because of their [[geochemical]] properties, rare-earth elements are typically dispersed and not often found concentrated in [[rare-earth mineral]]s. Consequently, economically exploitable [[ore|ore deposits]] are sparse.<ref name="Haxel02">{{cite web |url=http://pubs.usgs.gov/fs/2002/fs087-02/fs087-02.pdf |title=Rare Earth Elements—Critical Resources for High Technology |author=Haxel G. |author2=Hedrick J. |date=2002 |publisher=United States Geological Survey |editor=Peter H. Stauffer |editor2=James W. Hendley II |id=USGS Fact Sheet: 087-02 |access-date=2012-03-13 |quote=However, in contrast to ordinary base and [[precious metals]], REE have very little tendency to become concentrated in exploitable ore deposits. Consequently, most of the world's supply of REE comes from only a handful of sources, almost entirely as a byproduct of mining other elements in commercially exploitable concentrations they occur alongside. |author3=Orris J. |archive-date=December 14, 2010 |archive-url=https://web.archive.org/web/20101214095306/http://pubs.usgs.gov/fs/2002/fs087-02/fs087-02.pdf |url-status=live}}</ref> The first rare-earth mineral discovered (1787) was [[gadolinite]], a black mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of [[Ytterby]] in [[Sweden]]. Four of the rare-earth elements bear names derived from this single location.

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