Editing Tennessine (section)

===Pre-discovery===
In December&nbsp;2004, the [[Joint Institute for Nuclear Research]] (JINR) team in [[Dubna]], [[Moscow Oblast]], Russia, proposed a joint experiment with the [[Oak Ridge National Laboratory]] (ORNL) in [[Oak Ridge, Tennessee]], United States, to synthesize element&nbsp;117 — so called for the 117&nbsp;[[proton]]s in its [[atomic nucleus|nucleus]]. Their proposal involved [[nuclear fusion|fusing]] a [[berkelium]] (element&nbsp;97) target and a [[calcium]] (element&nbsp;20) beam, conducted via bombardment of the berkelium target with calcium nuclei:<ref name="elements">{{cite press release |last=Cabage |first=B. |date=2010 |title=International team discovers element&nbsp;117 |publisher=[[Oak Ridge National Laboratory]] |url=https://web.ornl.gov/info/ornlreview/v43_2_10/article02.shtml |url-status=dead |access-date=2017-06-26 |archive-url=https://web.archive.org/web/20150923175349/https://web.ornl.gov/info/ornlreview/v43_2_10/article02.shtml |archive-date=2015-09-23}}</ref> this would complete a set of experiments done at the JINR on the fusion of [[actinide]] targets with a calcium-48 beam, which had thus far produced the new elements [[nihonium|113]]–[[livermorium|116]] and [[oganesson|118]]. ORNL—then the world's only producer of berkelium—could not then provide the element, as they had temporarily ceased production,<ref name="elements" /> and re-initiating it would be too costly.<ref name="vanderbilt">{{cite press release |title=Vanderbilt physicist plays pivotal role in discovery of new super-heavy element |publisher=Vanderbilt University |date=April 2010 |url=https://news.vanderbilt.edu/2010/04/vanderbilt-physicist-plays-pivotal-role-in-discovery-of-new-super-heavy-element-112107/ |access-date=2016-06-12}}</ref> Plans to synthesize element&nbsp;117 were suspended in favor of the confirmation of element&nbsp;118, which had been produced earlier in 2002 by bombarding a [[californium]] target with calcium.<ref name="pp2002">{{cite journal |last1=Oganessian |first1=Yu.Ts. |last2=Utyonkov |first2=V.K. |last3=Lobanov |first3=Yu.V. |last4=Abdullin |first4=F.Sh. |last5=Polyakov |first5=A.N. |last6=Shirokovsky |first6=I.V. |last7=Tsyganov |first7=Yu.S. |last8=Mezentsev |first8=A.N. |display-authors=6 |year=2002 |title=Results from the first <sup>249</sup>Cf+<sup>48</sup>Ca experiment |journal=JINR Communication |url=https://www.jinr.ru/publish/Preprints/2002/287(D7-2002-287)e.pdf |access-date=2015-09-23}}</ref> The required berkelium-249 is a by-product in californium-252 production, and obtaining the required amount of berkelium was an even more difficult task than obtaining that of californium, as well as costly: It would cost around 3.5&nbsp;million dollars, and the parties agreed to wait for a commercial order of californium production, from which berkelium could be extracted.<ref name="vanderbilt" /><ref name="InsideScience" />

The JINR team sought to use berkelium because [[calcium-48]], the [[isotopes of calcium|isotope of calcium]] used in the beam, has 20&nbsp;protons and 28&nbsp;neutrons, making a neutron–proton ratio of 1.4; and it is the lightest stable or near-stable nucleus with such a large neutron excess. Thanks to the neutron excess, the resulting nuclei were expected to be heavier and closer to the sought-after [[island of stability]].{{efn|Although stable isotopes of the lightest elements usually have a neutron–proton ratio close or equal to one (for example, the only stable isotope of [[aluminium]] has 13&nbsp;protons and 14&nbsp;neutrons,{{NUBASE2020|ref}} making a neutron–proton ratio of 1.077), stable isotopes of heavier elements have higher neutron–proton ratios, increasing with the number of protons. For example, [[iodine]]'s only stable isotope has 53&nbsp;protons and 74&nbsp;neutrons, giving neutron–proton ratio of 1.396, [[gold]]'s only stable isotope has 79&nbsp;protons and 118 neutrons, yielding a neutron–proton ratio of 1.494, and [[plutonium]]'s most stable isotope has 94&nbsp;protons and 150&nbsp;neutrons, and a neutron–proton ratio of 1.596.{{NUBASE2020|ref}} This trend<ref>{{cite book |last1=Karpov |first1=A. V. |last2=Zagrebaev |first2=V. I. |last3=Palenzuela |first3=Y. Martinez |last4=Greiner |first4=Walter |year=2013 |chapter=Superheavy Nuclei: Decay and Stability |title=Exciting Interdisciplinary Physics |page=69 |series=FIAS Interdisciplinary Science Series |doi=10.1007/978-3-319-00047-3_6 |isbn=978-3-319-00046-6}}</ref> is expected to make it difficult to synthesize the most stable isotopes of super-heavy elements as the neutron–proton ratios of the elements they are synthesized from will be too low.}} Of the aimed for 117&nbsp;protons, calcium has 20, and thus they needed to use berkelium, which has 97&nbsp;protons in its nucleus.{{NUBASE2020|ref}}

In February&nbsp;2005, the leader of the JINR team — [[Yuri Oganessian]] — presented a colloquium at ORNL. Also in attendance were representatives of Lawrence Livermore National Laboratory, who had previously worked with JINR on the discovery of elements 113–116 and 118, and [[Joseph H. Hamilton|Joseph Hamilton]] of [[Vanderbilt University]], a collaborator of Oganessian.<ref name="Oganessian" />

Hamilton checked if the ORNL high-flux reactor produced californium for a commercial order: The required berkelium could be obtained as a by-product. He learned that it did not and there was no expectation for such an order in the immediate future. Hamilton kept monitoring the situation, making the checks once in a while. (Later, Oganessian referred to Hamilton as "the father of 117" for doing this work.)<ref name="Oganessian">{{cite news |title=What it takes to make a new element |magazine=Chemistry World |url=https://www.chemistryworld.com/what-it-takes-to-make-a-new-element/1017677.article |access-date=2016-12-03}}</ref>