Editing Flerovium (section)

===First signs===
The first sign of flerovium was found in December 1998 by a team of scientists at [[Joint Institute for Nuclear Research]] (JINR), [[Dubna]], Russia, led by [[Yuri Oganessian]], who bombarded a target of [[plutonium-244]] with accelerated nuclei of [[calcium-48]]:

:{{nuclide|plutonium|244}} + {{nuclide|calcium|48}} → {{nuclide|flerovium|292}}* → {{nuclide|flerovium|290}} + 2 {{nuclide|neutronium|1}}

This reaction had been tried before, without success; for this 1998 attempt, JINR had upgraded all of its equipment to detect and separate the produced atoms better and bombard the target more intensely.<ref name="Chapman">{{cite news|url=https://www.chemistryworld.com/what-it-takes-to-make-a-new-element/1017677.article|title= What it takes to make a new element|last=Chapman| first= Kit|date=November 30, 2016|magazine=Chemistry World|publisher= Royal Society of Chemistry|access-date=December 3, 2016}}</ref> One atom of flerovium, [[alpha decay]]ing with lifetime 30.4&nbsp;s, was detected. The [[decay energy]] measured was 9.71&nbsp;[[electronvolt|MeV]], giving an expected half-life of 2–23&nbsp;s.<ref name="99Og01" /> This observation was assigned to {{chem2|^{289}Fl}} and was published in January 1999.<ref name="99Og01">{{cite journal|last1=Oganessian
|first1=Yu. Ts.|display-authors=etal|date=1999|title=Synthesis of Superheavy Nuclei in the <sup>48</sup>Ca + <sup>244</sup>Pu Reaction|url=http://flerovlab.jinr.ru/linkc/flnr_presentations/articles/synthesis_of_Element_114_1999.pdf|journal=[[Physical Review Letters]]|volume=83|issue=16|page=3154|bibcode=1999PhRvL..83.3154O|doi=10.1103/PhysRevLett.83.3154|access-date=28 August 2013|archive-date=30 July 2020|archive-url=https://web.archive.org/web/20200730232521/http://flerovlab.jinr.ru/linkc/flnr_presentations/articles/synthesis_of_Element_114_1999.pdf|url-status=dead}}</ref> The experiment was later repeated, but an isotope with these decay properties was never observed again, so the exact identity of this activity is unknown. It may have been due to the [[nuclear isomer|isomer]] {{chem2|^{289m}Fl}},<ref name="00Og01" /><ref name="04OgJINRPP">{{cite journal|last=Oganessian|first=Yu. Ts.|display-authors=etal|date=2004|title=Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions <sup>233,238</sup>U, <sup>242</sup>Pu, and <sup>248</sup>Cm + <sup>48</sup>Ca|url=http://www.jinr.ru/publish/Preprints/2004/160(E7-2004-160).pdf|journal=[[Physical Review C]]|volume=70|issue=6|page=064609|bibcode=2004PhRvC..70f4609O|doi=10.1103/PhysRevC.70.064609|url-status=dead|archive-url=https://web.archive.org/web/20080528130343/http://www.jinr.ru/publish/Preprints/2004/160(E7-2004-160).pdf|archive-date=28 May 2008}}</ref> but because the presence of a whole series of longer-lived isomers in its decay chain would be rather doubtful, the most likely assignment of this chain is to the 2n channel leading to {{chem2|^{290}Fl}} and electron capture to {{chem2|^{290}Nh}}. This fits well with the systematics and trends of flerovium isotopes, and is consistent with the low beam energy chosen for that experiment, though further confirmation would be desirable via synthesis of {{chem2|^{294}Lv}} in a <sup>248</sup>Cm(<sup>48</sup>Ca,2n) reaction, which would alpha decay to {{chem2|^{290}Fl}}.<ref name="Hofmann2016" /> The [[RIKEN]] team reported possible synthesis of isotopes {{chem2|^{294}Lv}} and {{chem2|^{290}Fl}} in 2016 in a <sup>248</sup>Cm(<sup>48</sup>Ca,2n) reaction, but the alpha decay of {{chem2|^{294}Lv}} was missed, alpha decay of {{chem2|^{290}Fl}} to {{chem2|^{286}Cn}} was observed instead of electron capture to {{chem2|^{290}Nh}}, and the assignment to {{chem2|^{294}Lv}} instead of {{chem2|^{293}Lv}} was not certain.<ref name="Kaji" />

[[Glenn T. Seaborg]], a scientist at [[Lawrence Berkeley National Laboratory]] who had been involved in work to make such superheavy elements, had said in December 1997 that "one of his longest-lasting and most cherished dreams was to see one of these magic elements";<ref name="Sacks" /> he was told of the synthesis of flerovium by his colleague [[Albert Ghiorso]] soon after its publication in 1999. Ghiorso later recalled:<ref name="Seaborg-obituary" />

{{blockquote|I wanted Glenn to know, so I went to his bedside and told him. I thought I saw a gleam in his eye, but the next day when I went to visit him he didn't remember seeing me. As a scientist, he had died when he had that stroke.<ref name="Seaborg-obituary">{{cite news|last=Browne|first=M. W.|date=27 February 1999|title=Glenn Seaborg, Leader of Team That Found Plutonium, Dies at 86|url=https://www.nytimes.com/1999/02/27/us/glenn-seaborg-leader-of-team-that-found-plutonium-dies-at-86.html|access-date=26 August 2013|newspaper=[[The New York Times]]|archive-url=https://web.archive.org/web/20130522143152/http://www.nytimes.com/1999/02/27/us/glenn-seaborg-leader-of-team-that-found-plutonium-dies-at-86.html|archive-date=22 May 2013}}</ref>|Albert Ghiorso}}

Seaborg died two months later, on 25 February 1999.<ref name="Seaborg-obituary" />

In March 1999, the same team replaced the {{chem2|^{244}Pu}} target with {{chem2|^{242}Pu}} to make other flerovium isotopes. Two atoms of flerovium were produced as a result, each alpha-decaying with a half-life of 5.5 s. They were assigned as {{chem2|^{287}Fl}}.<ref name="99Og02">{{cite journal|last1=Oganessian|first1=Yu. Ts.|display-authors=etal|date=1999|title=Synthesis of nuclei of the superheavy element 114 in reactions induced by <sup>48</sup>Ca|journal=Nature|volume=400|issue=6741|page=242|bibcode=1999Natur.400..242O|doi=10.1038/22281|s2cid=4399615}}</ref> This activity has not been seen again either, and it is unclear what nucleus was produced. It is possible that it was an isomer <sup>287m</sup>Fl<ref name="04Og01" /> or from electron capture by <sup>287</sup>Fl, leading to <sup>287</sup>Nh and <sup>283</sup>Rg.<ref name="EXON1">{{cite conference|title=Remarks on the Fission Barriers of SHN and Search for Element 120|first1=S.|last1=Hofmann|first2=S.|last2=Heinz|first3=R.|last3=Mann|first4=J.|last4=Maurer|first5=G.|last5=Münzenberg|first6=S.|last6=Antalic|first7=W.|last7=Barth|first8=H. G.|last8=Burkhard|first9=L.|last9=Dahl|first10=K.|last10=Eberhardt|first11=R.|last11=Grzywacz|first12=J. H.|last12=Hamilton|first13=R. A.|last13=Henderson|first14=J. M.|last14=Kenneally|first15=B.|last15=Kindler|first16=I.|last16=Kojouharov|first17=R.|last17=Lang|first18=B.|last18=Lommel|first19=K.|last19=Miernik|first20=D.|last20=Miller|first21=K. J.|last21=Moody|first22=K.|last22=Morita|first23=K.|last23=Nishio|first24=A. G.|last24=Popeko|first25=J. B.|last25=Roberto|first26=J.|last26=Runke|first27=K. P.|last27=Rykaczewski|first28=S.|last28=Saro|first29=C.|last29=Schneidenberger|first30=H. J.|last30=Schött|first31=D. A.|last31=Shaughnessy|first32=M. A.|last32=Stoyer|first33=P.|last33=Thörle-Pospiech|first34=K.|last34=Tinschert|first35=N.|last35=Trautmann|first36=J.|last36=Uusitalo|first37=A. V.|last37=Yeremin|year=2016|conference=Exotic Nuclei|editor1-first=Yu. E.|editor1-last=Peninozhkevich|editor2-first=Yu. G.|editor2-last=Sobolev|book-title=Exotic Nuclei: EXON-2016 Proceedings of the International Symposium on Exotic Nuclei|pages=155–164|isbn=9789813226555}}</ref>