Editing Nobelium (section)

==Discovery==
[[File:AlfredNobel2.jpg|thumb|right|The element was named after [[Alfred Nobel]]]]
The discovery of element 102 was a complicated process and was claimed by groups from [[Sweden]], the [[United States]], and the [[Soviet Union]]. The first complete and incontrovertible report of its [[discovery of the chemical elements|detection]] only came in 1966 from the [[JINR|Joint Institute of Nuclear Research]] at [[Dubna]] (then in the Soviet Union).<ref name="93TWG">{{Cite journal |doi=10.1351/pac199365081757 |title=Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements |year=1993 |last1=Barber |first1=Robert C. |journal=Pure and Applied Chemistry |volume=65 |pages=1757 |last2=Greenwood |first2=Norman N. |last3=Hrynkiewicz |first3=Andrzej Z. |last4=Jeannin |first4=Yves P. |last5=Lefort |first5=Marc |last6=Sakai |first6=Mitsuo |last7=Úlehla |first7=Ivan M. |last8=Wapstra |first8=Aaldert Hendrik |last9=Wilkinson |first9=Denys H. |s2cid=195819585 |issue=8|doi-access=free }} (Note: for Part I see Pure and Applied Chemistry, vol. 63, no. 6, pp. 879–886, 1991)</ref>

The first announcement of the discovery of element 102 was announced by physicists at the Nobel Institute for Physics in Sweden in 1957. The team reported that they had bombarded a [[curium]] target with [[carbon-13]] ions for twenty-five hours in half-hour intervals. Between bombardments, [[ion-exchange]] chemistry was performed on the target. Twelve out of the fifty bombardments contained samples emitting (8.5&nbsp;±&nbsp;0.1)&nbsp;[[MeV]] [[alpha particle]]s, which were in drops which eluted earlier than [[fermium]] (atomic number ''Z''&nbsp;=&nbsp;100) and [[californium]] (''Z''&nbsp;=&nbsp;98). The [[half-life]] reported was 10&nbsp;minutes and was assigned to either <sup>251</sup>102 or <sup>253</sup>102, although the possibility that the alpha particles observed were from a presumably short-lived [[mendelevium]] (''Z''&nbsp;=&nbsp;101) isotope created from the electron capture of element 102 was not excluded.<ref name="93TWG" /> The team proposed the name ''nobelium'' (No) for the new element,<ref name="Silva16367" /><ref>{{cite journal |last1=Fields |first1=Peter R. |last2=Friedman |first2=Arnold M. |last3=Milsted |first3=John |last4=Atterling |first4=Hugo |last5=Forsling |first5=Wilhelm |last6=Holm |first6=Lennart W. |last7=Åström |first7=Björn |date=1 September 1957 |title=Production of the New Element 102 |journal=Physical Review |volume=107 |issue=5 |pages=1460–1462 |doi=10.1103/PhysRev.107.1460 |bibcode=1957PhRv..107.1460F }}</ref> which was immediately approved by IUPAC,<ref name="Emsley2011" /> a decision which the Dubna group characterized in 1968 as being hasty.<ref name="TWGresponse">{{cite journal |doi=10.1351/pac199365081815 |title=Responses on 'Discovery of the transfermium elements' by Lawrence Berkeley Laboratory, California; Joint Institute for Nuclear Research, Dubna; and Gesellschaft fur Schwerionenforschung, Darmstadt followed by reply to responses by the Transfermium Working Group |year=1993 |last1=Ghiorso |first1=Albert |last2=Seaborg |first2=Glenn T. |last3=Oganessian |first3=Yuri Ts. |last4=Zvara |first4=Ivo |last5=Armbruster |first5=Peter |last6=Hessberger |first6=F. P. |last7=Hofmann |first7=Sigurd |last8=Leino |first8=Matti E. |last9=Münzenberg |first9=Gottfried |last10=Reisdorf |first10=Willibrord |last11=Schmidt |first11=Karl-Heinz |journal=Pure and Applied Chemistry |volume=65 |issue=8 |pages=1815–1824 |doi-access=free }}</ref>

In 1958, scientists at the [[Lawrence Berkeley National Laboratory]] repeated the experiment. The Berkeley team, consisting of [[Albert Ghiorso]], [[Glenn T. Seaborg]], [[John R. Walton]] and [[Torbjørn Sikkeland]], used the new heavy-[[ion]] [[linear accelerator]] (HILAC) to bombard a curium target (95% <sup>244</sup>Cm and 5% <sup>246</sup>Cm) with <sup>13</sup>C and <sup>12</sup>C ions. They were unable to confirm the 8.5&nbsp;MeV activity claimed by the Swedes but were instead able to detect decays from fermium-250, supposedly the daughter of <sup>254</sup>102 (produced from the curium-246), which had an apparent [[half-life]] of ~3&nbsp;s. Probably this assignment was also wrong, as later 1963 Dubna work showed that the half-life of <sup>254</sup>No is significantly longer (about 50&nbsp;s). It is more likely that the observed alpha decays did not come from element 102, but rather from <sup>250m</sup>Fm.<ref name="93TWG" />

In 1959, the Swedish team attempted to explain the Berkeley team's inability to detect element 102 in 1958, maintaining that they did discover it. However, later work has shown that no nobelium isotopes lighter than <sup>259</sup>No (no heavier isotopes could have been produced in the Swedish experiments) with a half-life over 3&nbsp;minutes exist, and that the Swedish team's results are most likely from [[thorium]]-225, which has a half-life of 8&nbsp;minutes and quickly undergoes triple alpha decay to [[polonium]]-213, which has a decay energy of 8.53612&nbsp;MeV. This hypothesis is lent weight by the fact that thorium-225 can easily be produced in the reaction used and would not be separated out by the chemical methods used. Later work on nobelium also showed that the divalent state is more stable than the trivalent one and hence that the samples emitting the alpha particles could not have contained nobelium, as the divalent nobelium would not have eluted with the other trivalent actinides.<ref name="93TWG" /> Thus, the Swedish team later retracted their claim and associated the activity to background effects.<ref name="Emsley2011">{{cite book |first=John |last=Emsley |title=Nature's Building Blocks: An A-Z Guide to the Elements |url=https://books.google.com/books?id=4BAg769RfKoC&pg=PA368 |date=2011 |publisher=Oxford University Press |isbn=978-0-19-960563-7 |pages=368–9 }}</ref>

In 1959, the team continued their studies and claimed that they were able to produce an isotope that decayed predominantly by emission of an 8.3&nbsp;MeV alpha particle, with a [[half-life]] of 3 s with an associated 30% [[spontaneous fission]] branch. The activity was initially assigned to <sup>254</sup>102 but later changed to <sup>252</sup>102. However, they also noted that it was not certain that element 102 had been produced due to difficult conditions.<ref name="93TWG" /> The Berkeley team decided to adopt the proposed name of the Swedish team, "nobelium", for the element.<ref name="Emsley2011" />

:{{nuclide|curium|244}} + {{nuclide|carbon|12}} → {{nuclide|nobelium|256}}{{su|p=*}} → {{nuclide|nobelium|252}} + 4 {{su|b=0|p=1}}{{SubatomicParticle|neutron}}

Meanwhile, in Dubna, experiments were carried out in 1958 and 1960 aiming to synthesize element 102 as well. The first 1958 experiment bombarded [[plutonium-239]] and [[plutonium-241|-241]] with [[oxygen-16]] ions. Some alpha decays with energies just over 8.5&nbsp;MeV were observed, and they were assigned to <sup>251,252,253</sup>102, although the team wrote that formation of isotopes from [[lead]] or [[bismuth]] impurities (which would not produce nobelium) could not be ruled out. While later 1958 experiments noted that new isotopes could be produced from [[mercury (element)|mercury]], [[thallium]], lead, or bismuth impurities, the scientists still stood by their conclusion that element 102 could be produced from this reaction, mentioning a half-life of under 30&nbsp;seconds and a decay energy of (8.8&nbsp;±&nbsp;0.5)&nbsp;MeV. Later 1960 experiments proved that these were background effects. 1967 experiments also lowered the decay energy to (8.6&nbsp;±&nbsp;0.4)&nbsp;MeV, but both values are too high to possibly match those of <sup>253</sup>No or <sup>254</sup>No.<ref name="93TWG" /> The Dubna team later stated in 1970 and again in 1987 that these results were not conclusive.<ref name="93TWG" />

In 1961, Berkeley scientists claimed the discovery of [[lawrencium|element 103]] in the reaction of californium with [[boron]] and carbon ions. They claimed the production of the isotope <sup>257</sup>103, and also claimed to have synthesized an alpha decaying isotope of element 102 that had a half-life of 15&nbsp;s and alpha decay energy 8.2&nbsp;MeV. They assigned this to <sup>255</sup>102 without giving a reason for the assignment. The values do not agree with those now known for <sup>255</sup>No, although they do agree with those now known for <sup>257</sup>No, and while this isotope probably played a part in this experiment, its discovery was inconclusive.<ref name="93TWG" />

Work on element 102 also continued in Dubna, and in 1964, experiments were carried out there to detect alpha-decay daughters of element 102 isotopes by synthesizing element 102 from the reaction of a [[uranium-238]] target with [[neon]] ions. The products were carried along a [[silver]] catcher foil and purified chemically, and the isotopes <sup>250</sup>Fm and <sup>252</sup>Fm were detected. The yield of <sup>252</sup>Fm was interpreted as evidence that its parent <sup>256</sup>102 was also synthesized: as it was noted that <sup>252</sup>Fm could also be produced directly in this reaction by the simultaneous emission of an alpha particle with the excess neutrons, steps were taken to ensure that <sup>252</sup>Fm could not go directly to the catcher foil. The half-life detected for <sup>256</sup>102 was 8&nbsp;s, which is much higher than the more modern 1967 value of (3.2&nbsp;±&nbsp;0.2)&nbsp;s.<ref name="93TWG" /> Further experiments were conducted in 1966 for <sup>254</sup>102, using the reactions <sup>243</sup>[[americium|Am]](<sup>15</sup>[[nitrogen|N]],4n)<sup>254</sup>102 and <sup>238</sup>U(<sup>22</sup>Ne,6n)<sup>254</sup>102, finding a half-life of (50&nbsp;±&nbsp;10)&nbsp;s: at that time the discrepancy between this value and the earlier Berkeley value was not understood, although later work proved that the formation of the isomer <sup>250m</sup>Fm was less likely in the Dubna experiments than at the Berkeley ones. In hindsight, the Dubna results on <sup>254</sup>102 were probably correct and can be now considered a conclusive detection of element 102.<ref name="93TWG" />

One more very convincing experiment from Dubna was published in 1966 (though it was submitted in 1965), again using the same two reactions, which concluded that <sup>254</sup>102 indeed had a half-life much longer than the 3&nbsp;seconds claimed by Berkeley.<ref name="93TWG" /> Later work in 1967 at Berkeley and 1971 at the [[Oak Ridge National Laboratory]] fully confirmed the discovery of element 102 and clarified earlier observations.<ref name="Emsley2011" /> In December 1966, the Berkeley group repeated the Dubna experiments and fully confirmed them, and used this data to finally assign correctly the isotopes they had previously synthesized but could not yet identify at the time. Thus they claimed to have discovered nobelium in 1958 to 1961.<ref name="Emsley2011" />

:{{nuclide|uranium|238}} + {{nuclide|neon|22}} → {{nuclide|nobelium|260}}{{su|p=*}} → {{nuclide|nobelium|254}} + 6 {{su|b=0|p=1}}{{SubatomicParticle|neutron}}

[[File:Frederic and Irene Joliot-Curie.jpg|thumb|right|[[Frédéric Joliot]] and [[Irène Joliot-Curie]]]]
In 1969, the Dubna team carried out chemical experiments on element 102 and concluded that it behaved as the heavier homologue of [[ytterbium]]. The Russian scientists proposed the name ''joliotium'' (Jo) for the new element after [[Irène Joliot-Curie]], who had recently died, creating an [[Transfermium Wars|element naming controversy]] that would not be resolved for several decades, with each group using its own proposed names.<ref name="Emsley2011" /><ref>{{cite journal |last1=Karpenko |first1=V. |date=1980 |title=The Discovery of Supposed New Elements: Two Centuries of Errors |journal=Ambix |volume=27 |issue=2 |pages=77–102 |doi=10.1179/amb.1980.27.2.77}}</ref>

In 1992, the [[IUPAC]]-[[IUPAP]] Transfermium Working Group (TWG) reassessed the claims of discovery and concluded that only the Dubna work from 1966 correctly detected and assigned decays to nuclei with atomic number 102 at the time. The Dubna team are therefore officially recognised as the discoverers of nobelium, although it is possible that it was detected at Berkeley in 1959.<ref name="93TWG" /> This decision was criticized by Berkeley the following year, calling the reopening of the cases of elements 101 to 103 a "futile waste of time", while Dubna agreed with IUPAC's decision.<ref name="TWGresponse" />

In 1994, as part of an attempted resolution to the element naming controversy, IUPAC ratified names for elements 101–109. For element 102, it ratified the name ''nobelium'' (No) on the basis that it had become entrenched in the literature over the course of 30 years and that [[Alfred Nobel]] should be commemorated in this fashion.<ref name="IUPAC1997">{{cite journal |title=Names and symbols of transfermium elements |journal=Pure and Applied Chemistry |volume=69 |issue=12 |pages=2471–2473 |date=1997 |url=http://pac.iupac.org/publications/pac/pdf/1997/pdf/6912x2471.pdf |doi=10.1351/pac199769122471 }}</ref> Because of outcry over the 1994 names, which mostly did not respect the choices of the discoverers, a comment period ensued, and in 1995 IUPAC named element 102 ''flerovium'' (Fl) as part of a new proposal, after either [[Georgy Flyorov]] or his eponymous [[Flerov Laboratory of Nuclear Reactions]].<ref name="Haire">{{cite book |last1=Hoffmann |first1=Darleane C. |last2=Lee |first2=Diana M. |last3=Pershina |first3=Valeria |date=2006 |chapter=Transactinides and the future elements |editor-last=Morss |editor-first=Lester R. |editor2-last=Edelstein |editor2-first=Norman M. |editor3-last=Fuger |editor3-first=Jean |title=The Chemistry of the Actinide and Transactinide Elements |url=https://archive.org/details/chemistryactinid00katz |url-access=limited |edition=3rd |publisher=[[Springer (publisher)|Springer]] |page=[https://archive.org/details/chemistryactinid00katz/page/n2011 1660] |isbn=978-1-4020-3555-5 }}</ref> This proposal was also not accepted, and in 1997 the name ''nobelium'' was restored.<ref name="IUPAC1997" /> Today the name ''flerovium'', with the same symbol, refers to [[flerovium|element 114]].<ref name="IUPAC-names-114-116">{{cite press release |date=30 May 2012 |title=Element 114 is Named Flerovium and Element 116 is Named Livermorium |url=http://www.iupac.org/news/news-detail/article/element-114-is-named-flerovium-and-element-116-is-named-livermorium.html |publisher=[[International Union of Pure and Applied Chemistry|IUPAC]] |url-status=dead |archive-url=https://web.archive.org/web/20120602010328/http://www.iupac.org/news/news-detail/article/element-114-is-named-flerovium-and-element-116-is-named-livermorium.html |archive-date= 2 June 2012 }}</ref>