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{{infobox lutetium}}
'''Lutetium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Lu''' and [[atomic number]] 71. It is a silvery white [[metal]], which resists corrosion in dry air, but not in moist air. Lutetium is the last element in the [[lanthanide]] series, and it is traditionally counted among the [[rare earth element]]s; it can also be classified as the first element of the 6th-period [[transition metal]]s.<ref name="finally">{{cite journal|last=Scerri|first=E.|author-link=Eric Scerri|year=2012|journal=Chemistry International|volume=34|issue=4|url=http://www.iupac.org/publications/ci/2012/3404/ud.html|title=Mendeleev's Periodic Table Is Finally Completed and What To Do about Group 3?|url-status=live|archive-url=https://web.archive.org/web/20170705051357/https://www.iupac.org/publications/ci/2012/3404/ud.html|archive-date=5 July 2017|df=dmy-all|doi=10.1515/ci.2012.34.4.28|doi-access=free}}</ref>

Lutetium was independently discovered in 1907 by French scientist [[Georges Urbain]], Austrian mineralogist [[Freiherr|Baron]] [[Carl Auer von Welsbach]], and American chemist [[Charles James (chemist)|Charles James]].<ref name=":0">{{cite web|url=https://www.chemicool.com/elements/lutetium.html|title=Lutetium Element Facts / Chemistry}}</ref> All of these researchers found lutetium as an impurity in [[ytterbium]]. The dispute on the priority of the discovery occurred shortly after, with Urbain and Welsbach accusing each other of publishing results influenced by the published research of the other; the naming honor went to Urbain, as he had published his results earlier. He chose the name ''lutecium'' for the new element, but in 1949 the spelling was changed to ''lutetium''. In 1909, the priority was finally granted to Urbain and his names were adopted as official ones; however, the name ''cassiopeium'' (or later ''cassiopium'') for element 71 proposed by Welsbach was used by many German scientists until the 1950s.<ref>{{Cite web|url=https://www.chemistrylearner.com/lutetium.html|title=History of Lutetium|date=25 May 2018 }}</ref>

Lutetium is not a particularly abundant element, although it is significantly more common than [[silver]] in the Earth's crust. It has few specific uses. Lutetium-176 is a relatively abundant (2.5%) radioactive isotope with a half-life of about 38 billion years, used to [[Lutetium-hafnium dating|determine the age]] of minerals and [[meteorite]]s. Lutetium usually occurs in association with the element [[yttrium]]<ref>{{Cite web|url=https://www.vocabulary.com/dictionary/lutetium|title=lutetium - Dictionary Definition|website=Vocabulary.com|access-date=2020-03-06}}</ref> and is sometimes used in metal [[alloy]]s and as a [[catalyst]] in various chemical reactions. [[Lutetium (177Lu) oxodotreotide|<sup>177</sup>Lu-DOTA-TATE]] is used for [[radiopharmaceutical|radionuclide therapy]] (see [[Nuclear medicine]]) on neuroendocrine tumours. Lutetium has the highest [[Brinell scale|Brinell hardness]] of any lanthanide, at 890–1300 [[Pascal (unit)|MPa]].<ref>{{cite book|editor=Samsonov, G. V.|chapter=Mechanical Properties of the Elements|doi=10.1007/978-1-4684-6066-7_7|isbn=978-1-4684-6066-7|chapter-url=http://ihtik.lib.ru/2011.08_ihtik_nauka-tehnika/2011.08_ihtik_nauka-tehnika_3560.rar|title=Handbook of the physicochemical properties of the elements|pages=387–446|publisher=IFI-Plenum|place=New York, USA|year=1968|archive-url=https://web.archive.org/web/20150402123344/http://ihtik.lib.ru/2011.08_ihtik_nauka-tehnika/2011.08_ihtik_nauka-tehnika_3560.rar|archive-date=2015-04-02}}</ref>
<!------------<ref>{{cite news| url=http://www.iupac.org/reports/provisional/abstract04/connelly_310804.html|title =IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (online draft of an updated version of the "''Red Book''" IR 3-6)| date =2004| access-date = 2009-06-06}}</ref>----------------->

==Characteristics==
===Physical properties===
A lutetium atom has 71 electrons, arranged in the [[electron configuration|configuration]] &#91;[[xenon|Xe]]&#93;&nbsp;4f<sup>14</sup>5d<sup>1</sup>6s<sup>2</sup>.<ref name="Cotton">{{Greenwood&Earnshaw|page=1223}}</ref> Lutetium is generally encountered in the +3 oxidation state, having lost its two outermost 6s and the single 5d-electron. The lutetium atom is the smallest among the lanthanide atoms, due to the [[lanthanide contraction]],<ref>{{Cotton&Wilkinson5th|pages=776, 955}}</ref> and as a result lutetium has the highest density, melting point, and hardness of the lanthanides.<ref name="Parker">{{cite book| last=Parker | first= Sybil P.| title =Dictionary of Scientific and Technical Terms| edition =3rd| location = New York| publisher = McGraw-Hill| date = 1984}}</ref> As lutetium's 4f orbitals are highly stabilized only the 5d and 6s orbitals are involved in chemical reactions and bonding;<ref name=jensenlaw>{{cite web|url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/081.%20Periodic%20Table.pdf|last1=Jensen|first1=William B.|author-link=William B. Jensen|title=The Periodic Law and Table|date=2000|archive-url=https://web.archive.org/web/20201110113324/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/081.%20Periodic%20Table.pdf |access-date=10 December 2022|archive-date=2020-11-10 }}</ref><ref>{{cite journal | last1=Krinsky | first1=Jamin L. | last2=Minasian | first2=Stefan G. | last3=Arnold | first3=John | title=Covalent Lanthanide Chemistry Near the Limit of Weak Bonding: Observation of (CpSiMe<sub>3</sub>)<sub>3</sub>Ce−ECp* and a Comprehensive Density Functional Theory Analysis of Cp<sub>3</sub>Ln−ECp (E = Al, Ga) | journal=Inorganic Chemistry | publisher=American Chemical Society (ACS) | volume=50 | issue=1 | date=2010-12-08 | issn=0020-1669 | doi=10.1021/ic102028d | pages=345–357| pmid=21141834 }}</ref> thus it is characterized as a d-block rather than an f-block element,<ref name="Jensen2015">{{cite journal |last1=Jensen |first1=William B. |date=2015 |title=The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table: an update |url=https://link.springer.com/article/10.1007/s10698-015-9216-1 |journal=Foundations of Chemistry |volume=17 |pages=23–31 |doi=10.1007/s10698-015-9216-1 |s2cid=98624395 |access-date=28 January 2021 |archive-date=30 January 2021 |archive-url=https://web.archive.org/web/20210130011116/https://link.springer.com/article/10.1007/s10698-015-9216-1 |url-status=live |url-access=subscription }}</ref> and on this basis some consider it not to be a lanthanide at all, but a [[transition metal]] like its lighter congeners [[scandium]] and [[yttrium]].<ref>{{cite web |url=https://www.webelements.com/ |title=WebElements |last=Winter |first=Mark |date=1993–2022 |publisher=The University of Sheffield and WebElements Ltd, UK |access-date=5 December 2022 }}</ref><ref>{{cite book |last=Cowan |first=Robert D. |date=1981 |title=The Theory of Atomic Structure and Spectra |publisher=University of California Press |page=598 |isbn=978-0-520-90615-0}}</ref>

===Chemical properties and compounds===
{{main|Lutetium compounds}}
Lutetium's compounds almost always contain the element in the +3 oxidation state.<ref>{{cite web|url=https://www.britannica.com/science/lutetium|title=Lutetium}}</ref> Aqueous solutions of most lutetium salts are colorless and form white crystalline solids upon drying, with the common exception of the iodide, which is brown. The soluble salts, such as nitrate, sulfate and acetate form hydrates upon crystallization. The [[lutetium(III) oxide|oxide]], hydroxide, fluoride, carbonate, phosphate and [[oxalate]] are insoluble in water.<ref name="patnaik" />

Lutetium metal is slightly unstable in air at standard conditions, but it burns readily at 150&nbsp;°C to form lutetium oxide. The resulting compound is known to absorb water and [[carbon dioxide]], and it may be used to remove vapors of these compounds from closed atmospheres.<ref name="aaaaaa">{{cite book| pages = [https://archive.org/details/historyuseourear00kreb_356/page/n327 303]–304| title = The history and use of our earth's chemical elements: a reference guide | url = https://archive.org/details/historyuseourear00kreb_356| url-access = limited| last= Krebs| first= Robert E.| publisher =Greenwood Publishing Group| date = 2006| isbn =978-0-313-33438-2}}</ref> Similar observations are made during reaction between lutetium and water (slow when cold and fast when hot); lutetium hydroxide is formed in the reaction.<ref name="ffff">{{cite web| url =https://www.webelements.com/lutetium/chemistry.html| title =Chemical reactions of Lutetium| publisher=Webelements| access-date=2009-06-06}}</ref> Lutetium metal is known to react with the four lightest halogens to form [[halides|trihalides]]; except the fluoride they are soluble in water. {{Citation needed|date=December 2024}}

Lutetium dissolves readily in weak acids<ref name="aaaaaa" /> and dilute [[sulfuric acid]] to form solutions containing the colorless lutetium ions, which are coordinated by between seven and nine water molecules, the average being {{chem2|[Lu(H2O)8.2](3+)}}.<ref name="Persson2010">{{cite journal|last1=Persson|first1=Ingmar|title=Hydrated metal ions in aqueous solution: How regular are their structures?|journal=Pure and Applied Chemistry|volume=82|issue=10|date=2010|pages=1901–1917|issn=0033-4545|doi=10.1351/PAC-CON-09-10-22|doi-access=free}}</ref>

:{{chem2|2 Lu + 3 H2SO4 → 2 Lu(3+) + 3 SO4(2-) + 3 H2↑}}

===Oxidation states===

Lutetium is usually found in the +3 oxidation state, like most other lanthanides. However, it can also be in the 0, +1 and +2 states as well.
===Isotopes===
{{main|Isotopes of lutetium}}
Lutetium occurs on the Earth in two isotopes: lutetium-175 and lutetium-176. Out of these two, only the former is stable, making the element [[monoisotopic element|monoisotopic]]. The latter one, lutetium-176, decays via [[beta decay]] with a [[half-life]] of {{val|3.70|e=10|u=years}}; it makes up about 2.5% of natural lutetium.{{NUBASE2020|ref}}

To date, 40 [[synthetic radioisotope]]s of the element have been characterized, ranging in [[mass number]] from 149 to 188; the most stable such isotopes are lutetium-174 with a half-life of 3.31 years, and lutetium-173 with a half-life of 1.37 years. All of the remaining [[Radioactive decay|radioactive]] isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than half an hour. Isotopes lighter than the stable lutetium-175 decay via [[electron capture]] (to produce isotopes of [[ytterbium]]), with some [[alpha emission|alpha]] and [[positron emission]]; the heavier isotopes decay primarily via beta decay, producing [[hafnium]] isotopes.{{NUBASE2020|ref}} Experiments at the 
[[Facility for Rare Isotope Beams]] have reported lutetium-190 in fragments of platinum-198 colliding with a carbon target.<ref name=PRL132.7>{{cite journal |first1=O. B. |last1=Tarasov |first2=A. |last2=Gade |first3=K. |last3=Fukushima |display-authors=et al. |title=Observation of New Isotopes in the Fragmentation of <sup>198</sup>Pt at FRIB |journal=Physical Review Letters |volume=132 |date=2024 |issue=7 |article-number=072501 |doi=10.1103/PhysRevLett.132.072501|pmid=38427880 |bibcode=2024PhRvL.132g2501T |osti=2309727 }}</ref>

The element also has 43 known [[nuclear isomer]]s, of which the most stable of them are lutetium-177m3, with a half-life of 160.4 days, and lutetium-174m with a half-life of 142 days; longer than the ground states of all lutetium isotopes except 173-176.{{NUBASE2020|ref}}

==History==
Three scientists were involved in the discovery of lutetium:<ref name="Virginia">{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Confusing Years |journal=The Hexagon |date=2015 |pages=72–77 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20II.pdf |access-date=30 December 2019}}</ref> French scientist [[Georges Urbain]],<ref name="1st">{{cite journal|title=Un nouvel élément: le lutécium, résultant du dédoublement de l'ytterbium de Marignac|journal=Comptes Rendus|volume=145|date=1907|url=http://gallica.bnf.fr/ark:/12148/bpt6k3099v/f759.image.langEN|pages=759–762|last= Urbain|first= G.}}</ref> Austrian mineralogist Baron [[Carl Auer von Welsbach]],<ref name="Deu">{{cite journal|title=Die Zerlegung des Ytterbiums in seine Elemente|trans-title=Resolution of ytterbium into its elements|journal=Monatshefte für Chemie|volume=29|issue=2|date=1908|url=http://babel.hathitrust.org/cgi/pt?id=mdp.39015036977471;view=1up;seq=193|doi=10.1007/BF01558944|pages=181–225, 191|first=Carl A. von|last=Welsbach|s2cid=197766399}} On page 191, Welsbach suggested names for the two new elements: ''"Ich beantrage für das an das Thulium, beziehungsweise Erbium sich anschließende, in dem vorstehenden Teile dieser Abhandlung mit Yb II bezeichnete Element die Benennung: Aldebaranium mit dem Zeichen Ad — und für das zweite, in dieser Arbeit mit Yb I bezeichnete Element, das letzte in der Reihe der seltenen Erden, die Benennung: Cassiopeïum mit dem Zeichen Cp."'' (I request for the element that is attached to thulium or erbium and that was denoted by Yb II in the above part of this paper, the designation "Aldebaranium" with the symbol Ad — and for the element that was denoted in this work by Yb I, the last in the series of the rare earths, the designation "Cassiopeïum" with the symbol Cp.)</ref> and American chemist Charles James.<ref name=JamesPrimary>{{cite journal|author=James, C. |year=1907|url=https://books.google.com/books?id=TrhMAAAAYAAJ&pg=PA495 |title=A new method for the separation of the yttrium earths|journal=Journal of the American Chemical Society|volume=29|issue=4|pages=495–499|doi=10.1021/ja01958a010|bibcode=1907JAChS..29..495J }} In a footnote on page 498, James mentions that Carl Auer von Welsbach had announced " ... the presence of a new element Er, γ, which is undoubtedly the same as here noted, ... ." The article to which James refers is: C. Auer von Welsbach (1907) [https://books.google.com/books?id=myLzAAAAMAAJ&pg=PA935 "Über die Elemente der Yttergruppe, (I. Teil)"] (On the elements of the ytterbium group (1st part)), ''Monatshefte für Chemie und verwandte Teile anderer Wissenschaften'' (Monthly Journal for Chemistry and Related Fields of Other Sciences), '''27''' : 935-946.</ref><ref>{{cite web | title = Separation of Rare Earth Elements by Charles James | work = National Historic Chemical Landmarks | publisher = American Chemical Society | url = http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/earthelements.html | access-date = 2014-02-21 }}</ref> They found lutetium as an impurity in [[ytterbia]], which was thought by Swiss chemist [[Jean Charles Galissard de Marignac]] to consist entirely of [[ytterbium]]. Of the three, Urbain was the first to publish, followed by Welsbach; James was about to publish when he learned of Urbain's work, and thereafter gave up his claim and did not publish.<ref name=Kragh>{{cite book |last=Kragh |first=Helge |date=1996 |editor-last=Evans |editor-first=C. H. |title=Episodes from the History of the Rare Earth Elements |publisher=Kluwer Academic Publishers |pages=67–90 |chapter=Chapter 5. Elements No. 70, 71 and 72: Discoveries and Controversies |isbn=978-94-010-6614-3}}</ref> Despite staying out of the priority argument, James worked on a much larger scale and possessed the largest supply of lutetium at the time.<ref name="Emsley240">{{cite book| pages=240–242| url =https://books.google.com/books?id=Yhi5X7OwuGkC&pg=PA241| title =Nature's building blocks: an A-Z guide to the elements|first =John|last=Emsley| publisher=Oxford University Press| isbn = 978-0-19-850341-5| date=2001}}</ref>

Urbain and Welsbach proposed different names. Urbain chose ''neoytterbium'' for ytterbium and ''lutecium'' for the new element.<ref name="Fra">{{cite journal|title=Lutetium und Neoytterbium oder Cassiopeium und Aldebaranium -- Erwiderung auf den Artikel des Herrn Auer v. Welsbach.|date=1909|journal=Monatshefte für Chemie|volume=31|issue=10|doi=10.1007/BF01530262|first=G. |last=Urbain|page=1|s2cid=101825980|url=https://zenodo.org/record/1859372}}</ref>  Welsbach chose ''aldebaranium'' and ''cassiopeium'' (after [[Aldebaran]] and [[Cassiopeia (constellation)|Cassiopeia]]). Both authors accused the other man of publishing results based on their work.<ref name="Weeks">{{cite book |last1=Weeks |first1=Mary Elvira |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |location=Easton, PA |url=https://archive.org/details/discoveryoftheel002045mbp |edition=6th }}</ref><ref name="XVI">{{cite journal | author = Weeks, Mary Elvira |author-link=Mary Elvira Weeks| title = The discovery of the elements: XVI. The rare earth elements | journal = Journal of Chemical Education | year = 1932 | volume = 9 | issue = 10 | pages = 1751&ndash;1773 | doi = 10.1021/ed009p1751 | bibcode=1932JChEd...9.1751W}}</ref>
The [[Commission on Isotopic Abundances and Atomic Weights|International Commission on Atomic Weights]], which was then responsible for the attribution of new element names, settled the dispute in 1909 by granting priority to Urbain and adopting his choice for a name, one derived from the Latin ''[[Lutetia]]'' ([[Paris]]). This decision was based on the fact that the separation of lutetium from Marignac's ytterbium was first described by Urbain.<ref name="1st" /> 
Welsbach had achieved the separation before Urbain, but Urbain had published 44 days earlier. Since Urbain was on the commission which made the decision, its objectivity could be questioned and furthermore Welsbach protested that Urbain's spectral evidence was weak and argued that his rival's lutetium was very impure, but to no avail.<ref name=Kragh/> After Urbain's names were recognized, neoytterbium was reverted to ytterbium.<ref>{{cite journal |last1=Skelton |first1=Alasdair |last2=Thornton |first2=Brett F. |date=2017 |title=Iterations of ytterbium |url=https://www.nature.com/articles/nchem.2755 |journal=Nature Chemistry |volume=9 |issue= 4|page=402 |doi=10.1038/nchem.2755 |pmid=28338694 |bibcode=2017NatCh...9..402S |access-date=31 January 2024|url-access=subscription }}</ref> 

The controversy died down after 1910, only to be reignited with the discovery of element 72. Urbain claimed in 1911 to have discovered a new rare earth named [[celtium]] and identified it as element 72. However, [[Niels Bohr]] had demonstrated from his quantum theory that element 72 had to be a [[group 4 element]] and not a rare earth, and based on an idea by [[Fritz Paneth]], Bohr's friend [[George de Hevesy]] worked with [[Dirk Coster]] to search for it in [[zirconium]] minerals. This they succeeded in doing, discovering [[hafnium]] in 1923. This discovery announcement, being in direct conflict with Urbain's celtium, ignited a controversy on element 72 throughout the 1920s; the resulting investigations on the nature of Urbain's celtium, since it was not the same as hafnium, reopened the case on element 71. The physicists [[Hans M. Hansen]] and [[Sven Werner]], at Bohr's Copenhagen institute, found in 1923 that Welsbach's 1907 samples of cassiopeium had been pure element 71, while Urbain's 1907 lutecium samples only contained traces of element 71 and his 1911 samples identified as [[celtium]] were actually pure element 71 – confirming Welsbach's criticism.<ref name="rare-earth-handbook">{{cite book|last1=Thyssen|first1=Pieter|last2=Binnemans|first2=Koen|editor1-last=Gschneider|editor1-first=Karl A. Jr. |editor2-last=Bünzli|editor2-first=Jean-Claude|editor3-last=Pecharsky|editor3-first=Vitalij K.|chapter=Accommodation of the Rare Earths in the Periodic Table: A Historical Analysis|title=Handbook on the Physics and Chemistry of Rare Earths|date=2011|page=63|publisher=Elsevier|location=Amsterdam|isbn=978-0-444-53590-0|oclc=690920513|chapter-url=https://books.google.com/books?id=8SstnPFSzb0C&pg=PA66|access-date=2013-04-25}}</ref><ref name=Kragh/> The Copenhagen physicists then started a campaign to re-award priority for element 71 to Welsbach and replace the name lutetium with cassiopeium, writing to Welsbach in 1923 of their intentions. This campaign encountered success in the physics literature, but in spite of strong German and Scandinavian support for cassiopeium, lutetium remained embedded in most of the chemical literature, with the International Commission on Atomic Weights in 1930 accepting that element 72 was hafnium but using lutetium for element 71.<ref name=Kragh/>

In 1949, it was decided by the [[International Union of Pure and Applied Chemistry]] to recommend the name lutetium, since cassiopeium by then was only used in German and sometimes Dutch, and it was a difficult name to adapt to other languages; it was nonetheless clarified that this was not intended as a statement on priority. Urbain's spelling ''lutecium'' was changed to ''lutetium'', in order to derive the name from Latin ''Lutetia'' instead of French ''Lutèce''.<ref>{{cite book |last=Jensen |first=K. A. |date=1953 |title=Chemical Nomenclature |publisher=American Chemical Society |pages=38–48 |chapter=Chapter 5. Problems of an International Chemical Nomenclature}}</ref> Pure lutetium metal was first produced in 1953.<ref name="Emsley240" />

==Occurrence and production==
[[Image:Monazit - Mosambik, O-Afrika.jpg|thumb|Monazite]]
Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. Its principal commercial source is as a by-product from the processing of the rare earth [[phosphate]] mineral [[monazite]] ({{chem|[[cerium|Ce]],[[lanthanum|La]],...)[[phosphorus|P]]|[[oxygen|O]]|4}}<!----please don't touch the formula---->, which has concentrations of only 0.0001% of the element,<ref name="aaaaaa" /> not much higher than the abundance of lutetium in the Earth crust of about 0.5&nbsp;mg/kg. No lutetium-dominant minerals are currently known.<ref>{{cite web |url=https://www.mindat.org/ |title=Mindat.org |author=Hudson Institute of Mineralogy |date=1993–2018 |website=www.mindat.org |access-date=14 January 2018}}</ref> The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia. The world production of lutetium (in the form of oxide) is about 10 tonnes per year.<ref name="Emsley240" /> Pure lutetium metal is very difficult to prepare. It is one of the rarest and most expensive of the rare earth metals with the price about US$10,000 per kilogram, or about one-fourth that of [[gold]].<ref>{{cite news| publisher = USGS| title =Rare-Earth Metals| author = Hedrick, James B. | access-date = 2009-06-06| url =https://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/740798.pdf}}</ref><ref>{{cite book|title=Industrial Minerals and Rocks |chapter=Rare Earth Elements |author=Castor, Stephen B. |author2=Hedrick, James B. |publisher=Society for Mining, Metallurgy and Exploration |chapter-url=http://www.rareelementresources.com/i/pdf/RareEarths-CastorHedrickIMAR7.pdf |editor=Jessica Elzea Kogel, Nikhil C. Trivedi and James M. Barker |year=2006 |pages=769–792 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20091007100717/http://www.rareelementresources.com/i/pdf/RareEarths-CastorHedrickIMAR7.pdf |archive-date=2009-10-07 }}</ref>

Crushed minerals are treated with hot concentrated [[sulfuric acid]] to produce water-soluble sulfates of rare earths. [[Thorium]] precipitates out of solution as hydroxide and is removed. After that the solution is treated with [[ammonium oxalate]] to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in [[nitric acid]] that excludes one of the main components, [[cerium]], whose oxide is insoluble in HNO<sub>3</sub>. Several rare earth metals, including lutetium, are separated as a double salt with [[ammonium nitrate]] by crystallization. Lutetium is separated by [[ion exchange]]. In this process, rare-earth ions are [[Adsorption|adsorbed]] onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. Lutetium salts are then selectively washed out by suitable complexing agent. Lutetium metal is then obtained by [[redox|reduction]] of anhydrous Lu[[chlorine|Cl]]<sub>3</sub> or Lu[[fluorine|F]]<sub>3</sub> by either an [[alkali metal]] or [[alkaline earth metal]].<ref name="patnaik">{{cite book|last =Patnaik|first =Pradyot|date = 2003|title =Handbook of Inorganic Chemical Compounds|publisher = McGraw-Hill|page = 510|isbn =978-0-07-049439-8|url= https://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA243|access-date = 2009-06-06}}</ref>
 
: {{chem2|2 LuCl3 + 3 Ca → 2 Lu + 3 CaCl2}}

<sup>177</sup>Lu is produced by [[neutron activation]] of <sup>176</sup>Lu or by indirectly by neutron activation of <sup>176</sup>Yb followed by [[beta decay]]. The 6.693-day half-life allows transport from the production reactor to the point of use without significant loss in activity.<ref name=PillaiKnapp/>

==Applications==
Small quantities of lutetium have many speciality uses. 

=== Stable isotopes ===
Stable lutetium can be used as [[catalyst]]s in [[petroleum]] [[Cracking (chemistry)|cracking]] in [[oil refinery|refineries]] and can also be used in alkylation, [[hydrogenation]], and [[polymerization]] applications.<ref>{{RubberBible86th}}</ref>

[[Lutetium aluminium garnet]] ({{chem2|Al5Lu3O12}}) has been proposed for use as a lens material in high [[refractive index]] [[immersion lithography]].<ref>{{cite book| page=12| url=https://books.google.com/books?id=Sx39H8XR1FcC&pg=PA12| title =Advanced Processes for 193-NM Immersion Lithography| author =Wei, Yayi | author2 =Brainard, Robert L. | publisher=SPIE Press| date = 2009| isbn =978-0-8194-7557-2}}</ref> Additionally, a tiny amount of lutetium is added as a [[dopant]] to [[gadolinium gallium garnet]], which was used in [[magnetic bubble memory]] devices.<ref>{{Cite journal | doi = 10.1007/BF02655293| title = Three garnet compositions for bubble domain memories| journal = Journal of Electronic Materials| volume = 3| issue = 3| pages = 693–707| year = 1974| last1 = Nielsen | first1 = J. W.| last2 = Blank | first2 = S. L.| last3 = Smith | first3 = D. H.| last4 = Vella-Coleiro | first4 = G. P.| last5 = Hagedorn | first5 = F. B.| last6 = Barns | first6 = R. L.| last7 = Biolsi | first7 = W. A.| bibcode = 1974JEMat...3..693N| s2cid = 98828884}}</ref> Cerium-doped lutetium oxyorthosilicate is currently the preferred compound for detectors in [[positron emission tomography]] (PET).<ref>{{cite book| author = Wahl, R. L. |chapter = Instrumentation| title = Principles and Practice of Positron Emission Tomography| location = Philadelphia: Lippincott| publisher = Williams and Wilkins| date= 2002| page =51}}</ref><ref>{{Cite journal | doi = 10.1109/23.256710| title = Evaluation of cerium doped lutetium oxyorthosilicate (LSO) scintillation crystals for PET| journal = IEEE Transactions on Nuclear Science| volume = 40| issue = 4| pages = 1045–1047| year = 1993| last1 = Daghighian | first1 = F.| last2 = Shenderov | first2 = P.| last3 = Pentlow | first3 = K. S. | last4 = Graham | first4 = M. C. | last5 = Eshaghian | first5 = B.| last6 = Melcher | first6 = C. L. | last7 = Schweitzer | first7 = J. S. | bibcode = 1993ITNS...40.1045D| s2cid = 28011497}}</ref> Lutetium aluminium garnet (LuAG) is used as a phosphor in light-emitting diode light bulbs.<ref>{{cite web|first=Steve|last=Bush|title=Discussing LED lighting phosphors|url=http://www.electronicsweekly.com/news/products/led/discussing-led-lighting-phosphors-2014-03/|publisher=Electronic Weekly|date=14 March 2014|access-date=26 January 2017}}</ref><ref>{{cite journal|title = A19 LED bulbs: What's under the frosting?|journal = EE Times|issue = July 18|date = 2011|issn = 0192-1541|pages = 44–45|author = Simard-Normandin, Martine }}</ref>

[[Lutetium tantalate]] (LuTaO<sub>4</sub>) is the densest known stable white material (density 9.81&nbsp;g/cm<sup>3</sup>)<ref name="lu1">{{Cite journal| first1 = G.| first2 = G.| first3 = L.| first4 = M. | title = Luminescence of materials based on LuTaO4| last1 = Blasse | author-link1 = George Blasse | journal = Journal of Alloys and Compounds | volume = 209 | issue = 1–2| pages = 1–2 | year = 1994 | doi = 10.1016/0925-8388(94)91069-3| last2 = Dirksen| last3 = Brixner| last4 = Crawford}}</ref> and therefore is an ideal host for X-ray phosphors.<ref>{{cite book| url = https://books.google.com/books?id=lWlcJEDukRIC&pg=PA846| page=846|title = Phosphor handbook| author = Shionoya, Shigeo | publisher= CRC Press| date = 1998| isbn =978-0-8493-7560-6}}</ref><ref name="appl">{{cite book| page = 32| url = https://books.google.com/books?id=F0Bte_XhzoAC&pg=PA32| title = Extractive metallurgy of rare earths| author = Gupta, C. K. | author2 = Krishnamurthy, Nagaiyar | publisher =CRC Press| date = 2004| isbn =978-0-415-33340-5}}</ref> The only denser white material is [[thorium dioxide]], with density of 10&nbsp;g/cm<sup>3</sup>, but the thorium it contains is radioactive.

Lutetium is also a compound of several [[Scintillator|scintillating materials]], which convert X-rays to visible light. It is part of [[Lutetium–yttrium oxyorthosilicate|LYSO]], [[Lutetium aluminium garnet|LuAG]] and [[Lutetium(III) iodide|lutetium iodide]] scintillators.

Research indicates that lutetium-ion atomic clocks could provide greater accuracy than any existing atomic clock.<ref>{{cite journal | first1 = K.J. | last1 = Arnold | first2 = R. | last2 = Kaewuam | first3 = A. | last3 = Roy | first4 = T.R. | last4 = Tan | first5 = M.D. | last5 = Barrett | title = Blackbody radiation shift assessment for a lutetium ion clock | journal = Nature Communications | volume = 9 | issue = 1 | page = 1650 | year=2018 | doi=10.1038/s41467-018-04079-x | pmid = 29695720 | pmc = 5917023 | bibcode = 2018NatCo...9.1650A | arxiv = 1712.00240 }}</ref>

===Unstable isotopes===
The suitable half-life and decay mode made lutetium-176 used as a pure beta emitter, using lutetium which has been exposed to [[neutron activation]], and in [[lutetium–hafnium dating]] to date [[meteorite]]s.<ref>{{cite book| page=51| url=https://books.google.com/books?id=3uYmP0K5PXEC&pg=PA52| title =Lectures in Astrobiology| author = Muriel Gargaud| author2 = Hervé Martin| author3 = Philippe Claeys|publisher= Springer|date = 2007| isbn =978-3-540-33692-1}}</ref> 

The isotope <sup>177</sup>Lu emits low-energy beta particles and gamma rays and has a half-life around 7 days, positive characteristics for commercial applications, especially in therapeutic nuclear medicine.<ref name=PillaiKnapp>MR Pillai, Ambikalmajan, and Furn F Russ Knapp. "Evolving important role of lutetium-177 for therapeutic nuclear medicine." Current radiopharmaceuticals 8.2 (2015): 78-85.</ref>
The synthetic isotope [[Lutetium (177Lu) DOTA-octreotate|lutetium-177 bound to octreotate]] (a [[somatostatin]] analogue), is used experimentally in targeted [[radionuclide]] therapy for [[neuroendocrine tumors]].<ref>{{cite book| page=98| url=https://books.google.com/books?id=ZtRdbUNbPn8C&pg=PA98| title =Metal complexes in tumor diagnosis and as anticancer agents| author=Sigel, Helmut | publisher=CRC Press| date =2004| isbn =978-0-8247-5494-5}}</ref> Lutetium-177 is used as a radionuclide in neuroendocrine tumor therapy and bone pain palliation.<ref>{{Cite journal
 | pmid = 25771367
| year = 2015
| last1 = Balter
| first1 = H.
| title = 177Lu-Labeled Agents for Neuroendocrine Tumor Therapy and Bone Pain Palliation in Uruguay
| journal = Current Radiopharmaceuticals
| volume = 9
| issue = 1
| pages = 85–93
| last2 = Trindade
| first2 = V.
| last3 = Terán
| first3 = M.
| last4 = Gaudiano
| first4 = J.
| last5 = Ferrando
| first5 = R.
| last6 = Paolino
| first6 = A.
| last7 = Rodriguez
| first7 = G.
| last8 = Hermida
| first8 = J.
| last9 = De Marco
| first9 = E.
| last10 = Oliver
| first10 = P.
| doi = 10.2174/1874471008666150313112620
}}</ref><ref>{{Cite journal
 | pmid = 25771368
| year = 2015
| last1 = Carollo
| first1 = A.
| title = Lutetium-177 Labeled Peptides: The European Institute of Oncology Experience
| journal = Current Radiopharmaceuticals
| volume = 9
| issue = 1
| pages = 19–32
| last2 = Papi
| first2 = S.
| last3 = Chinol
| first3 = M.
| doi = 10.2174/1874471008666150313111633
}}</ref> 

[[Lutetium (177Lu) vipivotide tetraxetan|Lutetium (<sup>177</sup>Lu) vipivotide tetraxetan]] is a therapy for [[prostate cancer]], FDA approved in 2022.<ref>{{cite journal |last1=Fallah |first1=Jaleh |last2=Agrawal |first2=Sundeep |last3=Gittleman |first3=Haley |last4=Fiero |first4=Mallorie H. |last5=Subramaniam |first5=Sriram |last6=John |first6=Christy |last7=Chen |first7=Wei |last8=Ricks |first8=Tiffany K. |last9=Niu |first9=Gang |last10=Fotenos |first10=Anthony |last11=Wang |first11=Min |last12=Chiang |first12=Kelly |last13=Pierce |first13=William F. |last14=Suzman |first14=Daniel L. |last15=Tang |first15=Shenghui |last16=Pazdur |first16=Richard |last17=Amiri-Kordestani |first17=Laleh |last18=Ibrahim |first18=Amna |last19=Kluetz |first19=Paul G. |title=FDA Approval Summary: Lutetium Lu 177 Vipivotide Tetraxetan for Patients with Metastatic Castration-Resistant Prostate Cancer |journal=Clinical Cancer Research |date=1 May 2023 |volume=29 |issue=9 |pages=1651–1657 |doi=10.1158/1078-0432.CCR-22-2875|pmid=36469000 |pmc=10159870 }}</ref>

==Precautions==
Like other rare-earth metals, lutetium is regarded as having a low degree of toxicity, but its compounds should be handled with care nonetheless: for example, lutetium fluoride inhalation is dangerous and the compound irritates skin.<ref name="aaaaaa" /> Lutetium nitrate may be dangerous as it may explode and burn once heated. Lutetium oxide powder is toxic as well if inhaled or ingested.<ref name="aaaaaa" />

Similarly to the other rare-earth metals, lutetium has no known biological role, but it is found even in humans, concentrating in bones, and to a lesser extent in the liver and kidneys.<ref name="Emsley240" /> Lutetium salts are known to occur together with other lanthanide salts in nature; the element is the least abundant in the human body of all lanthanides.<ref name="Emsley240" /> Human diets have not been monitored for lutetium content, so it is not known how much the average human takes in, but estimations show the amount is only about several micrograms per year, all coming from tiny amounts absorbed by plants. Soluble lutetium salts are mildly toxic, but insoluble ones are not.<ref name="Emsley240" />

==See also==
{{Subject bar
|portal=Chemistry
|book1=Lutetium
|book2=Lanthanides
|book3=Period 6 elements
|book4=Group 3 elements
|book5=Chemical elements (sorted&nbsp;alphabetically)
|book6=Chemical elements (sorted by number)
|commons=y
|wikt=y
|wikt-search=lutetium
}}

==References==
{{Reflist|30em}}
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[[Category:Lutetium| ]]
[[Category:Chemical elements]]
[[Category:Lanthanides]]
[[Category:Transition metals]]
[[Category:Chemical elements with hexagonal close-packed structure]]