Editing Lanthanum (section)

==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''."''
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: [ 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.{{Citation needed|date=March 2025}}