Editing Promethium (section)

===Searches for element 61===
In 1902, Czech chemist [[Bohuslav Brauner]] found out that the differences in properties between neodymium and samarium were the largest between any two consecutive lanthanides in the sequence then known; as a conclusion, he suggested there was an element with intermediate properties between them.<ref name="61a">{{cite journal|title =A Revised Periodic Table: With the Lanthanides Repositioned|journal=Foundations of Chemistry|volume=7|issue=3|year=2005|doi=10.1007/s10698-004-5959-9|pages=203–233|first=Michael|last=Laing|s2cid=97792365}}</ref> This prediction was supported in 1914 by [[Henry Moseley]] who, having discovered that [[atomic number]] was an experimentally measurable property of elements, found that a few atomic numbers had no known corresponding elements: the gaps were [[Technetium|43]], 61, [[Hafnium|72]], [[Rhenium|75]], [[Astatine|85]], and [[Francium|87]].<ref>{{cite book|title=Atomic and Nuclear Physics: An Introduction in S.I. Units|edition=2nd|year=1968|publisher=Van Nostrand|page=109|last1=Littlefield |first1=Thomas Albert|last2=Thorley|first2=Norman}}</ref> With the knowledge of a gap in the periodic table several groups started to search for the predicted element among other rare earths in the natural environment.{{sfn|Lavrukhina|Pozdnyakov|1966|p=108}}<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="Marshall">{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Last Member |journal=The Hexagon |date=2016 |pages=4–9 |url=https://chemistry.unt.edu/sites/default/files/users/owj0001/rare%20earths%20III_0.pdf |access-date=30 December 2019 |archive-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127115101/https://chemistry.unt.edu/sites/default/files/users/owj0001/rare%20earths%20III_0.pdf |url-status=dead }}</ref>

The first claim of a discovery was published by Luigi Rolla and Lorenzo Fernandes of [[Florence]], Italy. After separating a mixture of a few rare earth elements nitrate concentrate from the [[Brazil]]ian mineral [[monazite]] by fractionated crystallization, they yielded a solution containing mostly samarium. This solution gave x-ray spectra attributed to samarium and element 61. In honor of their city, they named element 61 "florentium". The results were published in 1926, but the scientists claimed that the experiments were done in 1924.<ref>{{cite journal|doi=10.1002/zaac.19261570129|title=Über das Element der Atomnummer 61|year=1926|last1=Rolla|first1=Luigi|last2=Fernandes|first2=Lorenzo|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=157|issue=1 |pages=371–381|language=de}}</ref><ref>{{cite journal|doi=10.1038/120014c0|title=Florentium or Illinium?|year=1927|author=Noyes, W. A.|journal=Nature |volume=120|pages=14|issue=3009|bibcode=1927Natur.120...14N|s2cid=4094131|doi-access=free}}</ref><ref>{{cite journal|doi=10.1038/119637a0|title=Florentium or Illinium?|year=1927|author=Rolla, L.|journal=Nature |volume=119|pages=637|last2=Fernandes|first2=L.|issue=3000|bibcode=1927Natur.119..637R|s2cid=4127574}}</ref><ref>{{cite journal|doi=10.1002/zaac.19281690128|title=Florentium. II|year=1928 |author=Rolla, Luigi|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=169|pages=319–320|last2=Fernandes|first2=Lorenzo|issue=1 }}</ref><ref>{{cite journal |doi=10.1002/zaac.19271630104|title=Florentium|year=1927|author=Rolla, Luigi|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=163 |pages=40–42|last2=Fernandes |first2=Lorenzo|issue=1 }}</ref><ref>{{cite journal|doi=10.1002/zaac.19271600119|title=Über Das Element der Atomnummer 61 (Florentium)|year=1927|author=Rolla, Luigi|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=160|pages=190–192|last2=Fernandes|first2=Lorenzo|issue=1 }}</ref> Also in 1926, a group of scientists from the [[University of Illinois at Urbana–Champaign]], Smith Hopkins and Len Yntema published the discovery of element 61. They named it "illinium", after the university.<ref>{{cite journal |doi=10.1038/117792a0|title=The Element of Atomic Number 61; Illinium|year=1926|author=Harris, J. A.|journal=Nature|volume=117|pages=792|last2=Yntema|first2=L. F.|last3=Hopkins|first3=B. S.|issue=2953 |bibcode=1926Natur.117..792H|doi-access=free}}</ref><ref>{{cite journal|doi=10.1038/118084b0|title=The New Element of Atomic Number 61: Illinium|year=1926|author=Brauner, Bohuslav |journal=Nature|volume=118|pages=84–85|issue=2959|bibcode=1926Natur.118...84B|s2cid=4089909}}</ref><ref>{{cite journal|doi=10.1007/BF01490264|title=Über das Element 61 (Illinium)|year=1926 |author=Meyer, R. J.|journal=Naturwissenschaften|volume=14|pages=771|last2=Schumacher|first2=G.|last3=Kotowski|first3=A.|bibcode=1926NW.....14..771M|issue=33|s2cid=46235121}}</ref> Both of these reported discoveries were shown to be erroneous because the spectrum line that "corresponded" to element 61 was identical to that of [[didymium]]; the lines thought to belong to element 61 turned out to belong to a few impurities (barium, chromium, and platinum).{{sfn|Lavrukhina|Pozdnyakov|1966|p=108}}

<!----REFS!!!--->In 1934, [[Josef Mattauch]] finally formulated the [[Mattauch isobar rule|isobar rule]]. One of the indirect consequences of this rule was that element 61 was unable to form stable isotopes.{{sfn|Lavrukhina|Pozdnyakov|1966|p=108}}<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|year=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> From 1938, a nuclear experiment was conducted by H. B. Law et al. at the [[Ohio State University]]. Nuclides were produced in 1941 which were not radioisotopes of neodymium or samarium, and the name "cyclonium" was proposed, but there was a lack of chemical proof that element 61 was produced and the discovery was not largely recognized.{{sfn|Emsley|2011|p=428}}<ref>{{cite book |first1=Marco |last1=Fontani |first2=Mariagrazia |last2=Costa |first3=Mary Virginia |last3=Orna |trans-title=The Periodic Table's Shadow Side |title=The Lost Elements |publisher=Oxford University Press |place=New York |year=2015 |orig-year=2014 |isbn=978-0-19-938334-4 |pages=302–303}}</ref>