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{{Infobox lanthanum|block ref=d block}}
'''Lanthanum''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''La''' and [[atomic number]]&nbsp;57. It is a [[Hardness|soft]], [[ductility|ductile]], silvery-white [[metal]] that tarnishes slowly when exposed to air. It is the first and the prototype of the [[lanthanide]] series, a group of 15&nbsp;similar elements between lanthanum and [[lutetium]] in the [[periodic table]]. Lanthanum is traditionally counted among the [[rare-earth element]]s. Like most other rare-earth elements, its usual [[oxidation state]] is +3, although some compounds are known with an oxidation state of +2. Lanthanum has no biological role in humans but is used by some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.

Lanthanum usually occurs together with [[cerium]] and the other rare-earth elements. Lanthanum was first found by the Swedish chemist [[Carl Gustaf Mosander]] in 1839 as an impurity in [[cerium nitrate]]{{snd}} hence the name ''lanthanum'', from the [[ancient Greek]] {{lang|grc|λανθάνειν}} ({{transliteration|grc|lanthanein}}), meaning 'to lie hidden'. Although it is classified as a rare-earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as [[lead]]. In minerals such as [[monazite]] and [[bastnäsite]], lanthanum composes about a quarter of the lanthanide content.<ref>{{cite web |title=Monazite-(Ce) Mineral Data |url=http://webmineral.com/data/Monazite-(Ce).shtml |access-date=10 July 2016 |website=Webmineral}}</ref> It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923.

Lanthanum compounds have numerous applications including [[Catalysis|catalysts]], additives in glass, [[carbon arc lamp]]s for studio lights and projectors, ignition elements in [[lighter]]s and torches, [[hot cathode|electron cathodes]], [[scintillator]]s, and [[gas tungsten arc welding]] electrodes. [[Lanthanum carbonate]] is used as a [[phosphate binder]] to treat [[hyperphosphatemia|high levels of phosphate in the blood]] accompanied by [[kidney failure]].

==Characteristics==

===Physical===
Lanthanum is the first element and prototype of the lanthanide series. In the periodic table, it appears to the right of the [[alkaline earth metal]] [[barium]] and to the left of the lanthanide cerium. Lanthanum is generally considered the first of the f-block elements by authors writing on the subject.<ref name=Fluck>{{cite journal |last=Fluck |first=E. |year=1988 |title=New notations in the periodic table |journal=[[Pure and Applied Chemistry]] |volume=60 |issue=3 |pages=431–436 |s2cid=96704008 |doi=10.1351/pac198860030431 |url=http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |url-status=live |access-date=24 March 2012 |archive-url=https://web.archive.org/web/20120325152951/http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |archive-date=25 March 2012 }}</ref><ref>{{cite book |author1-link=Lev Landau |first1=L.D. |last1=Landau |author2-link=Evgeny Lifshitz |first2=E.M. |last2=Lifshitz |year=1958 |title=Quantum Mechanics: Non-relativistic theory |edition=1st |volume=3 |pages=256–257 |publisher=[[Pergamon Press]] }}</ref><ref name=Jensen1982>{{cite journal |first=W.B. |last=Jensen |author-link=William B. Jensen |year=1982 |title=The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table |journal=Journal of Chemical Education |volume=59 |issue=8 |pages=634–636 |bibcode=1982JChEd..59..634J |doi=10.1021/ed059p634}}</ref><ref name=Jensen2015>{{cite journal |last=Jensen |first=William B. |year=2015 |title=The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table: An update |journal=Foundations of Chemistry |volume=17 |pages=23–31 |doi=10.1007/s10698-015-9216-1 |s2cid=98624395 |url=https://link.springer.com/article/10.1007/s10698-015-9216-1 |access-date=28 January 2021 |url-access=subscription }}</ref><ref>{{cite journal |last=Scerri |first=Eric |date=18 January 2021 |title=Provisional report on discussions on group&nbsp;3 of the periodic table |journal=Chemistry International |volume=43 |issue=1 |pages=31–34 |doi=10.1515/ci-2021-0115 |doi-access=free |s2cid=231694898 }}</ref> The 57&nbsp;electrons of a lanthanum atom are arranged in the [[electron configuration|configuration]] [Xe]5d{{sup|1}}6s{{sup|2}}, with three valence electrons outside the noble gas core. In chemical reactions, lanthanum almost always gives up these three valence electrons from the 5d and 6s [[electron shell#Subshells|subshells]] to form the +3 oxidation state, achieving the stable configuration of the preceding noble gas [[xenon]].<ref name=Greenwood1106>{{harvp|Greenwood|Earnshaw|1984|p=1106}}</ref> Some lanthanum(II) compounds are also known, but they are usually much less stable.<ref name=patnaik>{{cite book |last=Patnaik |first=Pradyot |year=2003 |title=Handbook of Inorganic Chemical Compounds |publisher=McGraw-Hill |isbn=978-0-07-049439-8 |pages=444–446 |url={{Google books|plainurl=yes|id=Xqj-TTzkvTEC|page=243 }} |access-date=2009-06-06}}</ref><ref>{{cite journal |bibcode=2008AngCh.120.1510H |title=Lanthanum Does Form Stable Molecular Compounds in the +2 Oxidation State |last1=Hitchcock |first1=Peter B. |last2=Lappert |first2=Michael F. |last3=Maron |first3=Laurent |last4=Protchenko |first4=Andrey V. |journal=Angewandte Chemie |year=2008 |volume=120 |issue=8 |page=1510 |doi=10.1002/ange.200704887 }}</ref> Lanthanum monoxide (LaO) produces strong absorption bands in some [[stellar spectra]].<ref>{{cite journal |last1=Jevons |first1=W. |year=1928 |title=The band spectrum of lanthanum monoxide |journal=Proceedings of the Physical Society |volume=41 |issue=1 |page=520 |bibcode=1928PPS....41..520J |doi=10.1088/0959-5309/41/1/355 }}</ref>

Among the lanthanides, lanthanum is exceptional as it has no 4f electrons as a single gas-phase atom. Thus it is only very weakly [[paramagnetic]], unlike the strongly paramagnetic later lanthanides (with the exceptions of the last two, [[ytterbium]] and [[lutetium]], where the 4f shell is completely full).<ref>{{cite book |last1 = Cullity |first1 = B.D. |last2 = Graham |first2 = C.D. |year = 2011 |title = Introduction to Magnetic Materials |publisher = John Wiley & Sons |place = New York, NY |isbn = 9781118211496 }}</ref> However, the 4f shell of lanthanum can become partially occupied in chemical environments and participate in chemical bonding.<ref name=Wittig>{{cite conference |last = Wittig |first = Jörg |date = 19–24 March 1973 |title=Festkörper Probleme (plenary lecture) |lang=de |trans-title=Solid state problems (plenary lecture) |editor-last=Queisser |editor-first=H.J. |conference=The Divisions Semiconductor Physics, Surface Physics, Low Temperature Physics, High Polymers, Thermodynamics and Statistical Mechanics, of the German Physical Society |place=Münster, DE |publisher=Springer |isbn=978-3-528-08019-8 |series=Advances in Solid State Physics |volume=13 |publication-place=Berlin, DE / Heidelberg, DE |pages=375–396 |chapter=The pressure variable in solid state physics: What about 4f-band superconductors? |doi=10.1007/BFb0108579 }}</ref><ref>{{cite journal | last1=Krinsky | first1=Jamin L. | last2=Minasian | first2=Stefan G. | last3=Arnold | first3=John | date=2010-12-08 | title=Covalent lanthanide chemistry near the limit of weak bonding: Observation of {{chem|(Cp|Si|Me|3|)|3|Ce−E|Cp*}} and a comprehensive density functional theory analysis of {{chem|Cp|3|Ln−E|Cp}} (E = Al, Ga) | journal=Inorganic Chemistry | publisher=American Chemical Society (ACS) | volume=50 | issue=1 | pages=345–357 | issn=0020-1669 | doi=10.1021/ic102028d | pmid=21141834 }}</ref> For example, the melting points of the trivalent lanthanides (all but [[europium]] and ytterbium) are related to the extent of hybridisation of the 6s, 5d, and 4f electrons (lowering with increasing 4f involvement),<ref>{{cite book |last=Gschneidner |first=Karl A., Jr. |year=2016 |title=Handbook on the Physics and Chemistry of Rare Earths |isbn=978-0-444-63851-9 |editor-first=Jean-Claude G.  |editor-last=Bünzli |volume=50 |pages=12–16 |chapter=282&nbsp;Systematics |editor-last2=Vitalij K. Pecharsky}}</ref> and lanthanum has the second-lowest melting point among them: 920&nbsp;°C. (Europium and ytterbium have lower melting points because they delocalise about two electrons per atom rather than three.)<ref>{{cite book |last1 = Krishnamurthy |first1 = Nagaiyar |last2 = Gupta |first2 = Chiranjib Kumar |year = 2004 |title = Extractive Metallurgy of Rare Earths |publisher = CRC Press |isbn = 0-415-33340-7 }}</ref> This chemical availability of f orbitals justifies lanthanum's placement in the f-block despite its anomalous ground-state configuration<ref name=Hamilton>{{cite journal |last=Hamilton |first=David C. |date=1965 |title=Position of lanthanum in the periodic table |journal=American Journal of Physics |volume=33 |issue=8 |pages=637–640 |bibcode=1965AmJPh..33..637H |doi=10.1119/1.1972042}}</ref><ref name=JensenLr>{{cite report |last=Jensen |first=W.B. |year=2015 |title=Some comments on the position of lawrencium in the periodic table |url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |url-status=dead |archive-url=https://web.archive.org/web/20151223091325/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |archive-date=23 December 2015 |access-date=20 September 2015}}</ref> (which is merely the result of strong interelectronic repulsion making it less profitable to occupy the 4f shell, as it is small and close to the core electrons).<ref>{{Cite journal |last=Jørgensen |first=Christian |date=1973 |title=The Loose Connection between Electron Configuration and the Chemical Behavior of the Heavy Elements (Transuranics) |journal=Angewandte Chemie International Edition |volume=12 |issue=1 |pages=12–19 |doi=10.1002/anie.197300121}}</ref>

The lanthanides become harder as the series is traversed: as expected, lanthanum is a soft metal. Lanthanum has a relatively high [[resistivity]] of 615&nbsp;nΩm at room temperature; in comparison, the value for the good conductor aluminium is only 26.50&nbsp;nΩm.<ref name=Greenwood1429>{{harvp|Greenwood|Earnshaw|1984|p=1429}}</ref><ref name=CRC>{{RubberBible86th}}</ref> Lanthanum is the least volatile of the lanthanides.<ref name=radio>{{cite report |title=The Radiochemistry of the Rare Earths, Scandium, Yttrium, and Actinium |publisher=Los Alamos National Laboratory |place = Los Alamos, NM |url=http://library.lanl.gov/cgi-bin/getfile?rc000021.pdf |url-status=live |via=lanl.gov |access-date=2016-06-23 |archive-url=https://web.archive.org/web/20210831203424/https://library.lanl.gov/cgi-bin/getfile?rc000021.pdf |archive-date=2021-08-31 }}</ref> Like most of the lanthanides, lanthanum has a [[Hexagonal crystal system|hexagonal crystal structure]] at room temperature ({{mvar|α}}-La). At 310&nbsp;°C, lanthanum changes to a [[face-centered cubic]] structure ({{mvar|β}}-La), and at 865&nbsp;°C, it changes to a [[body-centered cubic]] structure ({{mvar|γ}}-La).<ref name=CRC/>

===Chemical===
As expected from [[periodic trend]]s, lanthanum has the largest [[atomic radius]] of the lanthanides. Hence, it is the most reactive among them, tarnishing quite rapidly in air, turning completely dark after several hours and can readily burn to form [[lanthanum(III) oxide]], {{chem|La|2|O|3}}, which is almost as [[Basic (chemistry)|basic]] as [[calcium oxide]].<ref>{{harvp|Greenwood|Earnshaw|1984|pp=1105–1107}}</ref> A centimeter-sized sample of lanthanum will corrode completely in a year as its oxide [[spallation|spalls]] off like iron [[rust]], instead of forming a protective oxide coating like [[aluminium]], [[scandium]], [[yttrium]], and [[lutetium]].<ref>{{Cite web |title=Rare-Earth Metal Long Term Air Exposure Test |url=http://www.elementsales.com/re_exp/index.htm |access-date=2009-08-08}}</ref> Lanthanum reacts with the [[halogen]]s at room temperature to form the trihalides, and upon warming will form [[binary compound]]s with the nonmetals nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic.<ref name="Greenwood1106" /><ref name="patnaik" /> Lanthanum reacts slowly with water to form [[lanthanum hydroxide|lanthanum(III) hydroxide]], {{chem|La|(OH)|3}}.<ref name=webelements>{{Cite web |title=Chemical reactions of lanthanum |url=https://www.webelements.com/lanthanum/chemistry.html |access-date=2009-06-06 |publisher=Webelements}}</ref> In dilute [[sulfuric acid]], lanthanum readily forms the aquated tripositive ion {{chem|[La|(H|2|O)|9|]|3+}}: This is colorless in aqueous solution since {{chem|La|3+}} has no d or f electrons.<ref name=webelements/> Lanthanum is the strongest and [[HSAB theory|hardest]] base among the [[rare earth element]]s, which is again expected from its being the largest of them.<ref name=Greenwood1434>{{harvp|Greenwood|Earnshaw|1984|p=1434}}</ref>

Some lanthanum(II) compounds are also known, but they are much less stable.<ref name=patnaik/><!-- Although mentioned in the section on physical properties, someone looking for chemical characteristics easily misses it their --> Therefore, in officially naming compounds of lanthanum its oxidation number always is to be mentioned.

===Isotopes===
[[File:Lanthanum stable nucleus.png|thumb|left|280px|Excerpt from the [[chart of nuclides]] showing stable isotopes (black) from barium ({{nobr| {{mvar|Z}} {{=}} 56 }}) to neodymium ({{nobr| {{mvar|Z}} {{=}} 60 }})]]
{{Main|Isotopes of lanthanum}}
Naturally occurring lanthanum is made up of two isotopes, the stable {{chem|139|La}} and the [[primordial nuclide|primordial long-lived radioisotope]] {{chem|138|La}}. {{chem|139|La}} is by far the most abundant, making up 99.911% of natural lanthanum: it is produced in the [[s-process]] (slow [[neutron]] capture, which occurs in low- to medium-mass stars) and the [[r-process]] (rapid neutron capture, which occurs in core-collapse [[supernova]]e). It is the only stable isotope of lanthanum.<ref>{{NUBASE 2020}}</ref> The very rare isotope {{chem|138|La}} is one of the few primordial [[odd–odd nuclei]], with a long half-life of {{nobr|1.03×{{10^|11}} years.}} It is one of the proton-rich [[p-nuclei]] which cannot be produced in the [[s-process|s-]] or [[r-process]]es. {{chem|138|La}}, along with the even rarer [[tantalum-180m|{{chem|180m|Ta}}]], is produced in the ν-process, where [[neutrino]]s interact with stable nuclei.<ref name=nu-process>{{cite journal |last1=Woosley |first1=S.E. |last2=Hartmann |first2=D.H. |last3=Hoffman |first3=R.D. |last4=Haxton |first4=W.C. |year=1990 |title=The ν-process |journal=The Astrophysical Journal |volume=356 |pages=272–301 |bibcode=1990ApJ...356..272W |doi=10.1086/168839}}</ref> All other lanthanum isotopes are [[synthetic radioisotope|synthetic]]: with the exception of {{chem|137|La}}, which has a half-life of about 60,000&nbsp;years, all of them have half-lives less than two days, and most have half-lives less than a minute. The isotopes {{chem|139|La}} and {{chem|140|La}} occur as [[fission product]]s of uranium.<ref>{{NUBASE 2020}}</ref>

==Compounds==

[[Lanthanum oxide]] is a white solid that can be prepared by direct reaction of its constituent elements. Due to the large size of the {{chem|La|3+}} ion, {{chem|La|2|O|3}} adopts a hexagonal 7-coordinate structure that changes to the 6-coordinate structure of [[scandium oxide]] ({{chem|Sc|2|O|3}}) and [[yttrium(III) oxide|yttrium oxide]] ({{chem|Y|2|O|3}}) at high temperature. When it reacts with water, [[lanthanum hydroxide]] is formed:<ref name=Shkolnikov2009>{{Cite journal |first=E.V. |last=Shkolnikov |year=2009 |title=Thermodynamic characterization of the amphoterism of hydroxides and oxides of scandium subgroup elements in aqueous media |journal=Russian Journal of Applied Chemistry |volume=82 |issue=2 |pages=2098–2104 |doi=10.1134/S1070427209120040 |s2cid=93220420}}</ref> a lot of heat is evolved in the reaction and a hissing sound is heard. Lanthanum hydroxide will react with atmospheric [[carbon dioxide]] to form the basic carbonate.<ref name=Greenwood1107>{{harvp|Greenwood|Earnshaw|1984|pp=1107–1108}}</ref>

[[Lanthanum fluoride]] is insoluble in water and can be used as a [[qualitative inorganic analysis|qualitative]] test for the presence of {{chem|La|3+}}. The heavier halides are all very soluble [[deliquescent]] compounds. The anhydrous halides are produced by direct reaction of their elements, as heating the hydrates causes hydrolysis: for example, heating hydrated {{chem|La|Cl|3}} produces {{chem|La|O|Cl}}.<ref name=Greenwood1107/>

Lanthanum reacts exothermically with hydrogen to produce the dihydride {{chem|La|H|2}}, a black, [[pyrophoricity|pyrophoric]], brittle, conducting compound with the [[calcium fluoride]] structure.<ref name=Fukai>{{cite book |last=Fukai |first=Y. |year=2005 |title=The Metal-Hydrogen System, Basic Bulk Properties |edition = 2nd |publisher=Springer |isbn=978-3-540-00494-3}}</ref> This is a non-stoichiometric compound, and further absorption of hydrogen is possible, with a concomitant loss of electrical conductivity, until the more salt-like {{chem|La|H|3}} is reached. Like {{chem|La|I|2}} and {{chem|La|I}}, {{chem|La|H|2}} is probably an [[electride]] compound.<ref name=Greenwood1107/>

Due to the large ionic radius and great electropositivity of {{chem|La|3+}}, there is not much covalent contribution to its bonding and hence it has a limited [[coordination chemistry]], like yttrium and the other lanthanides.<ref name=Greenwood1108>{{harvp|Greenwood|Earnshaw|1984|pp=1108–1109}}</ref> [[Lanthanum oxalate]] does not dissolve very much in alkali-metal oxalate solutions, and {{chem|[La(acac)|3|(H|2|O)|2|]}} decomposes around 500&nbsp;°C. Oxygen is the most common [[donor atom]] in lanthanum complexes, which are mostly ionic and often have high coordination numbers over {{nobr| 6 : 8 }} is the most characteristic, forming [[square antiprism]]atic and [[snub disphenoid|dodecadeltahedral]] structures. These high-coordinate species, reaching up to coordination number&nbsp;12 with the use of [[chelating ligand]]s such as in {{chem|La|2|(S|O|4|)|3| · 9(H|2|O)}}, often have a low degree of symmetry because of stereo-chemical factors.<ref name=Greenwood1108/>

Lanthanum chemistry tends not to involve {{nobr|{{mvar|π}}-bonding}} due to the electron configuration of the element: thus its organometallic chemistry is quite limited. The best characterized organolanthanum compounds are the [[cyclopentadienyl complex]] {{chem|La|(C|5|H|5|)|3}}, which is produced by reacting anhydrous {{chem|La|Cl|3}} with {{chem|Na|C|5|H|5}} in [[tetrahydrofuran]], and its methyl-substituted derivatives.<ref name=Greenwood1110>{{harvp|Greenwood|Earnshaw|1984|p=1110}}</ref>

==History==
[[File:Mosander Carl Gustav bw.jpg|thumb|right|[[Carl Gustaf Mosander]], the scientist who discovered lanthanum as well as [[terbium]] and [[erbium]]]]
In 1751, the Swedish mineralogist [[Axel Fredrik Cronstedt]] discovered a heavy mineral from the mine at [[Bastnäs]], later named [[cerite]]. Thirty years later, the fifteen-year-old [[Wilhelm Hisinger]], from the family owning the mine, sent a sample of it to [[Carl Scheele]], who did not find any new elements within. In 1803, after Hisinger had become an [[ironmaster]], he returned to the mineral with [[Jöns Jacob Berzelius]] and isolated a new oxide which they named ''ceria'' after the [[dwarf planet]] [[Ceres (dwarf planet)|Ceres]], which had been discovered two years earlier.<ref>{{Cite web |title=The Discovery and Naming of the Rare Earths |url=http://www.vanderkrogt.net/elements/rareearths.php |access-date=23 June 2016 |publisher=Elements.vanderkrogt.net}}</ref> Ceria was simultaneously independently isolated in Germany by [[Martin Heinrich Klaproth]].<ref name=Greenwood1424>{{harvp|Greenwood|Earnshaw|1984|p=1424}}</ref> Between 1839 and 1843, ceria was shown to be a mixture of oxides by the Swedish surgeon and chemist [[Carl Gustaf Mosander]], who lived in the same house as Berzelius and studied under him: he separated out two other oxides which he named ''lanthana'' and ''[[didymium|didymia]]''.<ref name=Weeks>{{cite book |last=Weeks |first=Mary Elvira |year=1956 |title=The discovery of the elements |publisher=Journal of Chemical Education |edition=6th |location=Easton, PA |url=https://archive.org/details/discoveryoftheel002045mbp}}</ref><ref name=XI>{{cite journal |last=Weeks |first=Mary Elvira |author-link=Mary Elvira Weeks |date=1932 |title=The discovery of the elements: XI. Some elements isolated with the aid of potassium and sodium: Zirconium, titanium, cerium, and thorium |journal=The Journal of Chemical Education |volume=9 |issue=7 |pages=1231–1243 |bibcode=1932JChEd...9.1231W |doi=10.1021/ed009p1231}}</ref> He partially decomposed a sample of [[cerium nitrate]] by roasting it in air and then treating the resulting oxide with dilute [[nitric acid]].{{efn|
From {{harvp|Berzelius|1839a|p=356}}: 
: ''"L'oxide de cérium, extrait de la cérite par la procédé ordinaire, contient à peu près les deux cinquièmes de son poids de l'oxide du nouveau métal qui ne change que peu les propriétés du cérium, et qui s'y tient pour ainsi dire caché. Cette raison a engagé M. Mosander à donner au nouveau métal le nom de ''Lantane''."''
::  
: [ The oxide of cerium, extracted from cerite by the usual procedure, contains almost two fifths of its weight in the oxide of the new metal, which differs only slightly from the properties of cerium, and which is held in it so to speak "hidden". This reason motivated Mr. Mosander to give to the new metal the name ''Lantane''. ]<ref>{{cite journal |last = Berzelius |year = 1839a |title = Nouveau métal |language = fr |trans-title = New metal |journal = [[Comptes rendus]] |volume = 8 |pages = 356–357; quote p&nbsp;356 |url = https://archive.org/stream/ComptesRendusAcademieDesSciences0008/ComptesRendusAcadmieDesSciences-Tome008-Janvier-juin1839#page/n361/mode/1up |via = Google books }}</ref>
}}<ref>{{cite magazine |last = Berzelius |year = 1839b|title = Latanium — a new metal |magazine = [[Philosophical Magazine]] |series = new series |volume = 14 |pages = 390–391 |url = https://books.google.com/books?id=dF1KiX7MbSMC&pg=PA390 |archive-url=https://web.archive.org/web/20221115194934/https://books.google.com/books?id=dF1KiX7MbSMC&pg=PA390 |archive-date=2022-11-15 }}</ref> That same year, [[Axel Erdmann]], a student also at the [[Karolinska Institute]], discovered lanthanum in a new mineral from [[Låven]] island located in a Norwegian fjord.

Finally, Mosander explained his delay, saying that he had extracted a second element from cerium, and this he called didymium. Although he did not realise it, didymium too was a mixture, and in 1885 it was separated into [[praseodymium]] and neodymium.

Since lanthanum's properties differed only slightly from those of cerium, and occurred along with it in its salts, he named it from the [[Ancient Greek]] {{math|{{Lang|grc|λανθάνειν}}}} [{{transliteration|grc|lanthanein}}] (lit. ''to lie hidden'').<ref name=Greenwood1424/> Relatively pure lanthanum metal was first isolated in 1923.<ref>{{Cite web|url=https://periodic.lanl.gov/57.shtml?hl=en-US|title=Lanthanum - Periodic Table of Elements: Los Alamos National Laboratory|access-date=2025-08-26}}</ref>

==Occurrence and production==
Lanthanum makes up 39&nbsp;mg/kg of the Earth's crust,<ref>{{cite web |title=It's elemental — the periodic table of elements |department = Education |website = jlab.org |publisher=[[Thomas Jefferson National Accelerator Facility]] |place = Newport News, VA |url=http://education.jlab.org/itselemental/index.html |url-status=live |archive-url=https://web.archive.org/web/20070429032414/http://education.jlab.org/itselemental/index.html |archive-date=29 April 2007 |access-date=2007-04-14 }}</ref><ref>{{cite book |chapter = Abundance of elements in the Earth’s crust and in the sea |title = CRC Handbook of Chemistry and Physics |edition = 97th |year = 2016–2017 |page = 14 }}</ref> behind [[neodymium]] at 41.5&nbsp;mg/kg and cerium at 66.5&nbsp;mg/kg. Despite being among the so-called "rare-earth metals", lanthanum is thus not rare at all, but it is historically named so because it is rarer than "common earths" such as [[Lime (material)|lime]] and [[Periclase|magnesia]], and at the time it was recognized only a few deposits were known. Lanthanum is also considered a "rare-earth" metal because the process to mine it is difficult, time-consuming, and expensive.<ref name=patnaik/> Lanthanum is rarely the dominant lanthanide found in the rare-earth minerals, and in their chemical formulas it is usually preceded by cerium. Rare examples of La-dominant minerals are monazite-(La) and lanthanite-(La).<ref>{{cite web |publisher=Hudson Institute of Mineralogy |date=1993–2018 |title=Mindat.org |url=https://www.mindat.org/ |access-date=14 January 2018 |website=mindat.org}}</ref>

[[File:Monazite acid cracking process.svg|class=skin-invert-image|thumb|center|upright=3|Production of lanthanum from monazite sand]]
The {{chem|La|3+}} ion is similarly sized to the early lanthanides of the cerium group (those up to [[samarium]] and [[europium]]) that immediately follow in the periodic table, and hence it tends to occur along with them in [[phosphate]], [[silicate]] and [[carbonate]] minerals, such as [[monazite]] ({{chem2|M^{III}PO4}}) and [[bastnäsite]] ({{chem2|M^{III}CO3F}}), where M refers to all the rare-earth metals except scandium and the radioactive [[promethium]] (mostly Ce, La, and Y).<ref>{{harvp|Greenwood|Earnshaw|1984|p=1103}}.</ref> Bastnäsite is usually lacking in [[thorium]] and the heavy lanthanides, and the purification of the light lanthanides from it is less involved. The ore, after being crushed and ground, is first treated with hot concentrated sulfuric acid, evolving carbon dioxide, [[hydrogen fluoride]], and [[silicon tetrafluoride]]: the product is then dried and leached with water, leaving the early lanthanide ions, including lanthanum, in solution.<ref name=Greenwood1426>{{harvp|Greenwood|Earnshaw|1984|pp=1426–1429}}.</ref>

The procedure for monazite, which usually contains all the rare earths as well as thorium, is more involved. Monazite, because of its magnetic properties, can be separated by repeated electromagnetic separation. After separation, it is treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with [[sodium hydroxide]] to pH&nbsp;3–4. Thorium precipitates out of solution as hydroxide and is removed. After that, the solution is treated with [[ammonium oxalate]] to convert rare earths to their insoluble [[oxalate]]s. 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 {{chem|H|N|O|3}}. Lanthanum is separated as a double salt with ammonium nitrate by crystallization. This salt is relatively less soluble than other rare-earth double salts and therefore stays in the residue.<ref name=patnaik/> Care must be taken when handling some of the residues as they contain [[radium-228|{{chem|228|Ra}}]], the daughter of {{chem|232|Th}}, which is a strong gamma emitter. Lanthanum is relatively easy to extract, as it has only one neighbouring lanthanide{{snd}} cerium, which can be removed by making use of its ability to be oxidised to the +4 state; thereafter, lanthanum may be separated out by the historical method of [[fractional crystallization (chemistry)|fractional crystallization]] of {{chem|La|(N|O|3|)|3|· 2 N|H|4|N|O|3|· 4 H|2|O}}, or by [[ion-exchange]] techniques when higher purity is desired.<ref name=Greenwood1426/>

Lanthanum metal is obtained from its oxide by heating it with [[ammonium chloride]] or fluoride and hydrofluoric acid at 300–400&nbsp;°C to produce the chloride or fluoride:<ref name=patnaik/>

: {{chem|La|2|O|3}} + {{chem|6 N|H|4|Cl}} {{math|→}} {{chem|2 La|Cl|3}} + {{chem|6 N|H|3}} + {{chem|3 H|2|O}}

This is followed by reduction with alkali or alkaline-earth metals in vacuum or argon atmosphere:<ref name=patnaik/>

: {{chem|La|Cl|3}} + {{chem|3 Li}} {{math|→}} {{chem|La}} + {{chem|3 Li|Cl}}

Also, pure lanthanum can be produced by electrolysis of molten mixture of anhydrous {{chem|La|Cl|3}} and {{chem|Na|Cl}} or {{chem|K|Cl}} at elevated temperatures.<ref name=patnaik/>

==Applications==
The first historical application of lanthanum was in gas lantern [[gas mantle|mantles]]. [[Carl Auer von Welsbach]] used a mixture of [[lanthanum oxide]] and [[zirconium dioxide|zirconium oxide]], which he called ''Actinophor'' and patented in 1886. The original mantles gave a green-tinted light and were not very successful, and his first company, which established a factory in [[Atzgersdorf]] in 1887, failed in 1889.<ref>{{cite book |editor-last=Evans |editor-first=C.H. |date=2012-12-06 |title=Episodes from the History of the Rare Earth Elements |publisher=Kluwer Academic Publishers |isbn=9789400902879 |page=122  |url=https://books.google.com/books?id=EFzuCAAAQBAJ&q=Welsbach+Actinophor+Atzgersdorf&pg=PA122}}</ref>

Modern uses of lanthanum include:
[[Image:LaB6HotCathode.jpg|thumb|{{chem|La|B|6}} hot cathode]]
* One material used for anodic material of [[Nickel–metal hydride battery|nickel–metal hydride batteries]] is {{chem|La|(Ni|3.6|Mn|0.4|Al|0.3|Co|0.7|)}}. Due to high cost to extract the other lanthanides, a [[mischmetal]] with more than 50% of lanthanum is used instead of pure lanthanum. The compound is an [[Intermetallics|intermetallic]] component of the {{chem|A|B|5}} type.<ref>{{Cite web |title=Inside the Nickel Metal Hydride Battery |url=http://www.cobasys.com/pdf/tutorial/inside_nimh_battery_technology.pdf |url-status=dead |archive-url=https://web.archive.org/web/20090227062546/http://www.cobasys.com/pdf/tutorial/inside_nimh_battery_technology.pdf |archive-date=2009-02-27 |access-date=2009-06-06}}</ref><ref>{{Cite journal |last1=Tliha |first1=M. |last2=Mathlouthi |first2=H. |last3=Lamloumi |first3=J. |last4=Percheronguegan |first4=A. |date=2007 |title=AB5-type hydrogen storage alloy used as anodic materials in Ni-MH batteries |journal=Journal of Alloys and Compounds |volume=436 |issue=1–2 |pages=221–225 |doi=10.1016/j.jallcom.2006.07.012}}</ref> [[NiMH]] batteries can be found in many models of the [[Toyota Prius]] sold in the US.  These larger nickel-metal hydride batteries require massive quantities of lanthanum for the production. The 2008 Toyota Prius NiMH battery requires {{convert|10|to|15|kg|lb}} of lanthanum. As engineers push the technology to increase fuel efficiency, twice that amount of lanthanum could be required per vehicle.<ref>{{Cite news |date=2009-08-31 |title=As hybrid cars gobble rare metals, shortage looms |publisher=Reuters 2009-08-31 |url=https://www.reuters.com/article/ousiv/idUSTRE57U02B20090831}}</ref><ref>{{Cite journal |last1=Bauerlein |first1=P. |last2=Antonius |first2=C. |last3=Loffler |first3=J. |last4=Kumpers |first4=J. |date=2008 |title=Progress in high-power nickel–metal hydride batteries |journal=Journal of Power Sources |volume=176 |issue=2 |pages=547 |bibcode=2008JPS...176..547B |doi=10.1016/j.jpowsour.2007.08.052}}</ref><ref>{{Cite web |date=19 November 2015 |title=Why Toyota offers 2 battery choices in next Prius |url=https://www.autonews.com/article/20151123/OEM06/311239986/why-toyota-offers-2-battery-choices-in-next-prius}}</ref>
* Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process. Heat energy is released every time they do so; therefore these alloys have possibilities in energy conservation systems.<ref name=CRC/><ref>{{Cite journal |last=Uchida |first=H. |date=1999 |title=Hydrogen solubility in rare earth based hydrogen storage alloys |journal=International Journal of Hydrogen Energy |volume=24 |issue=9 |pages=871–877 |doi=10.1016/S0360-3199(98)00161-X|bibcode=1999IJHE...24..871U }}</ref>
* [[Mischmetal]], a [[pyrophoric]] alloy used in lighter flints, contains 25% to 45% lanthanum.<ref name=CRC_81st>{{cite book |first=C.R. |last=Hammond |year=2000 |chapter=The Elements |title=Handbook of Chemistry and Physics |publisher=CRC press |isbn=978-0-8493-0481-1 |edition=81st}}</ref>
* [[Lanthanum oxide]] and the [[lanthanum hexaboride|boride]] are used in electronic [[vacuum tube]]s as [[hot cathode]] materials with strong emissivity of [[electron]]s. Crystals of {{chem| link = lanthanum hexaboride|La|B|6}} are used in high-brightness, extended-life, thermionic electron emission sources for [[electron microscope]]s and [[Hall-effect thruster]]s.<ref>{{Cite journal |first1=Jason D. |last1=Sommerville |first2=Lyon B. |last2=King |name-list-style=amp |title=Effect of Cathode Position on Hall-Effect Thruster Performance and Cathode Coupling Voltage |url=http://sgc.engin.umich.edu/erps/IEPC_2007/PAPERS/IEPC-2007-078.pdf |url-status=dead |journal=43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 8–11 July 2007, Cincinnati, OH |archive-url=https://web.archive.org/web/20110720091007/http://sgc.engin.umich.edu/erps/IEPC_2007/PAPERS/IEPC-2007-078.pdf |archive-date=July 20, 2011 |access-date=2009-06-06}}</ref>
* [[Lanthanum trifluoride]] ({{chem|La|F|3}}) is an essential component of a heavy fluoride glass named [[ZBLAN]]. This glass has superior transmittance in the infrared range and is therefore used for fiber-optical communication systems.<ref name=rutg>{{cite report |last=Harrington |first=James A. |title=Infrared fiber optics |publisher=[[Rutgers University]] |url=http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |archive-url=https://web.archive.org/web/20100802120432/http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |archive-date=2010-08-02 }}</ref>
* Cerium-doped [[Lanthanum(III) bromide|lanthanum bromide]] and [[Lanthanum(III) chloride|lanthanum chloride]] are the recent inorganic [[scintillator]]s, which have a combination of high light yield, best energy resolution, and fast response. Their high yield converts into superior energy resolution; moreover, the light output is very stable and quite high over a very wide range of temperatures, making it particularly attractive for high-temperature applications. These scintillators are already widely used commercially in detectors of [[neutrons]] or<!-- "and"? --> [[gamma rays]].<ref>{{cite web |title=BrilLanCe-NxGen |department=Detectors |website=oilandgas.saint-gobain.com |url=http://www.oilandgas.saint-gobain.com/uploadedFiles/SGoilandgas/Documents/Detectors/Detectors-BrilLanCe-NxGen-Packaging.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110429014149/http://www.oilandgas.saint-gobain.com/uploadedFiles/SGoilandgas/Documents/Detectors/Detectors-BrilLanCe-NxGen-Packaging.pdf |archive-date=2011-04-29 |access-date=2009-06-06}}</ref>
* [[Carbon arc lamp]]s use a mixture of rare earth elements to improve the light quality. This application, especially by the [[film|motion picture]] industry for studio lighting and projection, consumed about 25% of the rare-earth compounds produced until the phase out of carbon arc lamps.<ref name=CRC/><ref>{{cite report |last=Hendrick |first=James B. |year=1985 |title=Mineral Facts and Problems |publisher=Bureau of Mines |page=655 |id=Bulletin&nbsp;675 |url=https://digital.library.unt.edu/ark:/67531/metadc12817/ |chapter-url=https://digital.library.unt.edu/ark:/67531/metadc12817/m1/663/?q=%22carbon%20arc%22 |chapter=Rare Earth Elements and Yttrium}}</ref>
* [[Lanthanum(III) oxide]] ({{chem|La|2|O|3}}) improves the alkali resistance of [[glass]] and is used in making special optical glasses, such as infrared-absorbing glass, as well as [[camera]] and [[telescope]] [[Lens (optics)|lenses]], because of the high [[refractive index]] and low dispersion of rare-earth glasses.<ref name=CRC/> Lanthanum oxide is also used as a grain-growth additive during the liquid-phase [[sintering]] of [[silicon nitride]] and [[zirconium diboride]].<ref>{{cite journal |last1=Kim, K |last2=Shim |first2=Kwang Bo |year=2003 |title=The effect of lanthanum on the fabrication of ZrB2–ZrC composites by spark plasma sintering |journal=Materials Characterization |volume=50 |pages=31–37 |doi=10.1016/S1044-5803(03)00055-X}}</ref>
* Small amounts of lanthanum added to [[steel]] improves its [[malleability]], resistance to impact, and [[ductility]], whereas addition of lanthanum to [[molybdenum]] decreases its hardness and sensitivity to temperature variations.<ref name=CRC/>
* Small amounts of lanthanum are present in many pool products to remove the phosphates that feed algae.<ref>{{cite book |title=Pool Care Basics |pages=25–26  |url={{Google books|plainurl=yes|id=Kr3NCY4GJaAC|page=25 }} }}</ref>
* Lanthanum oxide additive to tungsten is used in [[gas tungsten arc welding]] electrodes, as a substitute for [[radioactive]] thorium.<ref>{{cite book |first=Howard B. |last=Cary |year=1995 |title=Arc Welding Automation |publisher=CRC Press |isbn=978-0-8247-9645-7 |page=139  |url={{Google books|plainurl=yes|id=H3BgQGdTP_0C }} }}</ref><ref>{{cite book |first=Larry |last=Jeffus |title=Welding : Principles and applications |year=2003 |publisher=Thomson/Delmar Learning |isbn=978-1-4018-1046-7 |location=Clifton Park, N.Y. |page=350 |chapter=Types of Tungsten |chapter-url={{Google books|plainurl=yes|id=zeRiW7en7HAC|page=RA1-PA750 }} |archive-url=https://web.archive.org/web/20100923150541/http://www.cmc.dk/ |archive-date=2010-09-23 |url-status=dead}}</ref>
* Various compounds of lanthanum and other rare-earth elements (oxides, chlorides, [[Lanthanide trifluoromethanesulfonates|triflates]], etc.) are components of various catalysis, such as [[petroleum cracking]] [[catalyst]]s.<ref>{{Cite book |last1=C. K. Gupta |url={{Google books|plainurl=yes|id=F0Bte_XhzoAC|page=441 }} |title=Extractive metallurgy of rare earths |last2=Nagaiyar Krishnamurthy |date=2004 |publisher=CRC Press |isbn=978-0-415-33340-5 |page=441}}</ref>
* Lanthanum-barium [[radiometric dating]] is used to estimate age of rocks and ores, though the technique has limited popularity.<ref>{{Cite journal |last1=S. Nakai |last2=A. Masuda |last3=B. Lehmann |date=1988 |title=La-Ba dating of bastnaesite |url=http://www.minsocam.org/ammin/AM73/AM73_1111.pdf |journal=American Mineralogist |volume=7 |issue=1–2 |page=1111 |bibcode=1988ChGeo..70...12N |doi=10.1016/0009-2541(88)90211-2}}</ref>
* [[Lanthanum carbonate]] was approved as a medication (Fosrenol, [[Shire Pharmaceuticals]]) to absorb excess [[phosphate]] in cases of [[hyperphosphatemia]] seen in [[end-stage kidney disease]].<ref name=fosrenol>{{Cite web |date=28 October 2004 |title=FDA approves Fosrenol(R) in end-stage renal disease (ESRD) patients |url=http://www.medicalnewstoday.com/articles/15538.php |url-status=dead |archive-url=https://web.archive.org/web/20090426054033/http://www.medicalnewstoday.com/articles/15538.php |archive-date=2009-04-26 |access-date=2009-06-06}}</ref>
* Lanthanum fluoride is used in phosphor lamp coatings. Mixed with europium fluoride, it is also applied in the crystal membrane of [[Fluoride selective electrode|fluoride ion-selective electrodes]].<ref name=patnaik/>
* Like [[horseradish peroxidase]], lanthanum is used as an [[Electron density|electron-dense tracer]] in [[molecular biology]].<ref>{{Cite journal |last1=Chau YP |last2=Lu KS |date=1995 |title=Investigation of the blood-ganglion barrier properties in rat sympathetic ganglia by using lanthanum ion and horseradish peroxidase as tracers |journal=Acta Anatomica |volume=153 |issue=2 |pages=135–144 |doi=10.1159/000313647 |issn=0001-5180 |pmid=8560966}}</ref>
* Lanthanum-modified bentonite (or [[phoslock]]) is used to remove phosphates from water in lake treatments.<ref>{{Cite journal |last1=Hagheseresht |last2=Wang |first2=Shaobin |last3=Do |first3=D. D. |date=2009 |title=A novel lanthanum-modified bentonite, Phoslock, for phosphate removal from wastewaters |journal=Applied Clay Science |volume=46 |issue=4 |pages=369–375 |doi=10.1016/j.clay.2009.09.009|bibcode=2009ApCS...46..369H }}</ref>
* Lanthanum telluride ({{chem|La|3|Te|4}}) is considered to be applied in the field of radioisotope power system (nuclear power plant) due to its significant conversion capabilities. The transmuted elements and isotopes in the segment will not react with the material itself, thus presenting no harm to the safety of the power plant.  Though iodine, which can be generated during transmutation, is suspected to react with {{chem|La|3|Te|4}} segment, the quantity of iodine is small enough to pose no threat to the power system.<ref>{{Cite book |last1=R. Smith |first1=Michael B. |last2=Whiting |first2=Christopher |last3=Barklay |first3=Chad |title=2019 IEEE Aerospace Conference |chapter=Nuclear Considerations for the Application of Lanthanum Telluride in Future Radioisotope Power Systems |date=2019 |pages=1–11 |doi=10.1109/AERO.2019.8742136 |isbn=978-1-5386-6854-2 |osti=1542236 |s2cid=195221607}}</ref>

==Biological role==
Lanthanum has no known biological role in humans. The element is very poorly absorbed after oral administration and when injected its elimination is very slow. [[Lanthanum carbonate]] (Fosrenol) was approved as a [[phosphate binder]] to absorb excess phosphate in cases of [[end stage renal disease]].<ref name=fosrenol/>

While lanthanum has pharmacological effects on several receptors and ion channels, its specificity for the [[gamma-Aminobutyric acid|GABA]] receptor is unique among trivalent cations. Lanthanum acts at the same modulatory site on the [[GABA receptor]] as [[zinc]], a known negative [[allosteric]] modulator. The lanthanum cation {{chem|La|3+}} is a positive allosteric modulator at native and recombinant GABA receptors, increasing open channel time and decreasing desensitization in a subunit configuration dependent manner.<ref>{{cite journal |last=Boldyreva |first = A.A. |year=2005 |title=Lanthanum potentiates GABA-activated currents in rat pyramidal neurons of CA1 hippocampal field |journal=Bulletin of Experimental Biology and Medicine |volume=140 |issue=4 |pages=403–5 |doi=10.1007/s10517-005-0503-z |pmid=16671565 |s2cid=13179025}}</ref>

Lanthanum is a cofactor for the [[methanol dehydrogenase]] of the [[methanotrophic]] bacterium ''[[Methylacidiphilum fumariolicum]]'' SolV, although the great chemical similarity of the lanthanides means that it may be substituted with cerium, praseodymium, or neodymium without ill effects, and with the smaller samarium, europium, or gadolinium giving no side effects other than slower growth.<ref>{{cite journal |last1=Pol |first1=Arjan |last2=Barends |first2=Thomas R.M. |last3=Dietl |first3=Andreas |last4=Khadem |first4=Ahmad F. |last5=Eygensteyn |first5=Jelle |last6=Jetten |first6=Mike S. M. |last7=Op Den Camp |first7=Huub J. M. |date=2013 |title=Rare earth metals are essential for methanotrophic life in volcanic mudpots |journal=Environmental Microbiology |volume=16 |issue=1 |pages=255–64 |doi=10.1111/1462-2920.12249 |pmid=24034209|bibcode=2014EnvMi..16..255P |url=https://repository.ubn.ru.nl//bitstream/handle/2066/128108/128108.pdf }}</ref>

==Precautions==
{{Chembox
| container_only = yes
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS02}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|260}}
| PPhrases = {{P-phrases|223|231+232|370+378|422}}<ref>{{cite web |title=Lanthanum 261130 |url=https://www.sigmaaldrich.com/catalog/product/aldrich/261130 |website=Sigma-Aldrich}}</ref>
| NFPA-H = 0
| NFPA-F = 4
| NFPA-R = 2
| NFPA-S = w
| NFPA_ref = 
 }}
}}
Lanthanum has no known biological impact.<ref name=Emsley>{{cite book |last=Emsley |first=John |year=2011 |title=Nature's Building Blocks: An A-Z guide to the elements |publisher=Oxford University Press |isbn=9780199605637 |pages=266–77}}</ref>{{rp|274|q=The metal has no biological role, and it has almost no impact on living things.}} In two cases exposure to carbon arc light led to findings of lanthanum and other rare-earth elements in lung tissue.<ref>{{cite journal |last1=Dufresne |first1=A. |last2=Krier |first2=G. |last3=Muller |first3=J. |last4=Case |first4=B. |last5=Perrault |first5=G. |date=1994 |title=Lanthanide particles in the lung of a printer |journal=Science of the Total Environment |volume=151 |issue=3 |pages=249–252 |bibcode=1994ScTEn.151..249D |doi=10.1016/0048-9697(94)90474-X |pmid=8085148}}</ref><ref>{{Cite journal |last1=Waring |first1=P.M. |last2=Watling |first2=R.J. |date=1990 |title=Rare earth deposits in a deceased movie projectionist. A new case of rare earth pneumoconiosis |journal=The Medical Journal of Australia |volume=153 |issue=11–12 |pages=726–30 |doi=10.5694/j.1326-5377.1990.tb126334.x |pmid=2247001 |s2cid=24985591}}</ref> Oral lanthanum carbonate is used to treat [[hyperphosphatemia]] by intercepting dietary [[phosphorus]].<ref name=Emsley/>{{rp|275}}<ref>{{cite journal |vauthors=Evans NS, Aronowitz P, Altertson TE |date=October 30, 2023 |title=Coin-shaped opacities in the stomach |department=JAMA Clinical Challenge |journal=[[Journal of the American Medical Association]] |volume=330 |issue=20 |pages=2016–2017 |doi=10.1001/jama.2023.19032 |pmid=37902730 |s2cid=264589220 |url=https://jamanetwork.com/journals/jama/fullarticle/2811509 |url-access=subscription }}</ref>

==Prices==
The price for a (metric) ton [1000&nbsp;kg] of ''Lanthanum oxide 99% (FOB China in USD/Mt)'' is given by the Institute of Rare Earths Elements and Strategic Metals (IREESM) as below $2,000 for most of the period from early 2001 to September 2010 (at $10,000 in the short term in 2008); it rose steeply to $140,000 in mid-2011 and fell back just as rapidly to $38,000 by early 2012.<ref>{{cite web |title = Lanthanum |website = institut-seltene-erden.de |url = https://en.institut-seltene-erden.de/seltene-erden-und-metalle/seltene-erden/lanthan/ |access-date=27 October 2022 }} — site gives specifications and notation</ref> The average price for the last six months (April–September&nbsp;2022) is given by the IREESM as follows: ''Lanthanum Oxide - 99.9%min FOB China - 1308 EUR/mt'' and for ''Lanthanum Metal - 99%min FOB China - 3706 EUR/mt''.<ref>{{cite web |title = ISE Metal-quotes |website = institut-seltene-erden.de |url=https://en.institut-seltene-erden.de/ |access-date=27 October 2022}} — site gives information and notation</ref>

==Notes==
{{notelist}}

==References==
{{reflist|25em}}

==Bibliography==
* {{Greenwood&Earnshaw1st}}{{Sfn whitelist|CITEREFGreenwoodEarnshaw1984}}

==Further reading==
* {{cite book |first = R.J. |last = Callow |year = 1967 |title = The Industrial Chemistry of the Lanthanons, Yttrium, Thorium and Uranium |publisher = Pergamon Press }}
* {{cite book |first1 = C.K. |last1 = Gupta |first2 = N. |last2 = Krishnamurthy |year = 2005 |title = Extractive Metallurgy of Rare Earths |publisher = CRC Press }}
* {{cite book |editor-first = P. |editor-last = Pascal |year = 1959 |title = Nouveau Traité de Chimie Minérale |language = fr |trans-title = New Treatise on Mineral Chemistry |volume = VII&nbsp;Scandium, Yttrium, Elements des Terres Rares, Actinium |publisher = Masson & Cie  }}
* {{cite book |first = R.C. |last = Vickery |year = 1953 |title = Chemistry of the Lanthanons |publisher = Butterworths }}

{{Periodic table (navbox)}}
{{Lanthanum compounds}}
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[[Category:Lanthanum| ]]
[[Category:Chemical elements]]
[[Category:Chemical elements with double hexagonal close-packed structure]]
[[Category:Lanthanides]]
[[Category:Reducing agents]]
[[Category:GABAA receptor positive allosteric modulators]]
[[Category:Rare earth elements]]