Editing Dubnium (section)

== Discovery ==
===Background===
[[Uranium]], element 92, is the heaviest element to occur in significant quantities in nature; heavier elements can only be practically produced by synthesis. The first synthesis of a new element—[[neptunium]], element 93—was achieved in 1940 by a team of researchers in the United States.<ref>{{Cite book|title=Radiochemistry and Nuclear Chemistry|last1=Choppin|first1=G. R.|last2=Liljenzin|first2=J.-O.|last3=Rydberg|first3=J.|publisher=[[Elsevier]]|year=2002|isbn=978-0-7506-7463-8|page=416}}</ref> In the following years, American scientists synthesized the elements up to [[mendelevium]], element 101, which was synthesized in 1955. From [[nobelium|element 102]], the priority of discoveries was contested between American and Soviet physicists.<ref>{{cite report|url=http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/28/017/28017156.pdf |archive-url=https://web.archive.org/web/20171009195038/http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/28/017/28017156.pdf |archive-date=2017-10-09 |url-status=live|title=The Transuranium Elements: From Neptunium and Plutonium to Element 112|last=Hoffman|first=D. C.|publisher=Lawrence Livermore National Laboratory|access-date=October 10, 2017|year=1996}}</ref> Their rivalry resulted in a race for new elements and credit for their discoveries, later named the [[Transfermium Wars]].<ref>{{cite journal | journal = Chemical & Engineering News | date = 1994 | volume = 74 | issue = 22 | pages = 2–3 | title = The Transfermium Wars | first=P. | last=Karol| doi = 10.1021/cen-v072n044.p002 | doi-access = free }}</ref>

=== Reports ===
[[File:Transactinide chemistry apparatus Dubna.jpg|thumb|left|Apparatus at Dubna used for the chemical characterization of elements [[rutherfordium|104]], 105, and [[seaborgium|106]]<ref name="Zvara">{{cite journal|first = I. J.|last = Zvara|date = 2003|title = Dubnium|journal = Chemical and Engineering News|url = http://pubs.acs.org/cen/80th/dubnium.html|volume = 81|issue = 36|page = 182|doi = 10.1021/cen-v081n036.p182|access-date = October 9, 2017|archive-date = December 31, 2017|archive-url = https://web.archive.org/web/20171231000415/http://pubs.acs.org/cen/80th/dubnium.html|url-status = live}}</ref>]]
The first report of the [[discovery of the chemical elements|discovery of element 105]] came from the [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], [[Moscow Oblast]], [[Soviet Union]], in April 1968. The scientists bombarded [[americium-243|<sup>243</sup>Am]] with a beam of [[neon-22|<sup>22</sup>Ne]] ions, and reported 9.4&nbsp;MeV (with a half-life of 0.1–3 seconds) and 9.7&nbsp;MeV (''t''<sub>1/2</sub>&nbsp;>&nbsp;0.05&nbsp;s) [[alpha decay|alpha activities]] followed by alpha activities similar to those of either <sup>256</sup>103 or <sup>257</sup>103. Based on prior theoretical predictions, the two activity lines were assigned to <sup>261</sup>105 and <sup>260</sup>105, respectively.<ref name="1993 report" />

:{{nuclide|americium|243}} + {{nuclide|neon|22}} → <sup>265−''x''</sup>105 + ''x'' {{SubatomicParticle|neutron}} (''x'' = 4, 5)

After observing the alpha decays of element 105, the researchers aimed to observe [[spontaneous fission]] (SF) of the element and study the resulting fission fragments. They published a paper in February 1970, reporting multiple examples of two such activities, with half-lives of 14&nbsp;ms and {{val|2.2|0.5|u=s}}. They assigned the former activity to <sup>242mf</sup>Am{{efn|This notation signifies that the nucleus is a [[nuclear isomer]] that decays via spontaneous fission.}} and ascribed the latter activity to an isotope of element 105. They suggested that it was unlikely that this activity could come from a transfer reaction instead of element 105, because the yield ratio for this reaction was significantly lower than that of the <sup>242mf</sup>Am-producing transfer reaction, in accordance with theoretical predictions. To establish that this activity was not from a (<sup>22</sup>Ne,''x''n) reaction, the researchers bombarded a <sup>243</sup>Am target with <sup>18</sup>O ions; reactions producing <sup>256</sup>103 and <sup>257</sup>103 showed very little SF activity (matching the established data), and the reaction producing heavier <sup>258</sup>103 and <sup>259</sup>103 produced no SF activity at all, in line with theoretical data. The researchers concluded that the activities observed came from SF of element 105.<ref name="1993 report" />

In April 1970, a team at [[Lawrence Berkeley National Laboratory|Lawrence Berkeley Laboratory]] (LBL), in [[Berkeley, California|Berkeley]], [[California]], United States, claimed to have synthesized element 105 by bombarding [[californium-249]] with [[nitrogen-15]] ions, with an alpha activity of 9.1&nbsp;MeV. To ensure this activity was not from a different reaction, the team attempted other reactions: bombarding <sup>249</sup>Cf with <sup>14</sup>N, Pb with <sup>15</sup>N, and Hg with <sup>15</sup>N. They stated no such activity was found in those reactions. The characteristics of the daughter nuclei matched those of <sup>256</sup>103, implying that the parent nuclei were of <sup>260</sup>105.<ref name="1993 report" />

:{{nuclide|californium|249}} + {{nuclide|nitrogen|15}} → <sup>260</sup>105 + 4 {{SubatomicParticle|neutron}}

These results did not confirm the JINR findings regarding the 9.4&nbsp;MeV or 9.7&nbsp;MeV alpha decay of <sup>260</sup>105, leaving only <sup>261</sup>105 as a possibly produced isotope.<ref name="1993 report" />

JINR then attempted another experiment to create element 105, published in a report in May 1970. They claimed that they had synthesized more nuclei of element 105 and that the experiment confirmed their previous work. According to the paper, the isotope produced by JINR was probably <sup>261</sup>105, or possibly <sup>260</sup>105.<ref name="1993 report" /> This report included an initial chemical examination: the thermal gradient version of the gas-chromatography method was applied to demonstrate that the chloride of what had formed from the SF activity nearly matched that of [[Niobium(V) chloride|niobium pentachloride]], rather than [[hafnium tetrachloride]]. The team identified a 2.2-second SF activity in a volatile chloride portraying eka-tantalum properties, and inferred that the source of the SF activity must have been element 105.<ref name="1993 report" />

In June 1970, JINR made improvements on their first experiment, using a purer target and reducing the intensity of transfer reactions by installing a [[collimator]] before the catcher. This time, they were able to find 9.1&nbsp;MeV alpha activities with daughter isotopes identifiable as either <sup>256</sup>103 or <sup>257</sup>103, implying that the original isotope was either <sup>260</sup>105 or <sup>261</sup>105.<ref name="1993 report" />

=== Naming controversy ===
{{multiple image
| footer = Danish nuclear physicist [[Niels Bohr]] and German nuclear chemist [[Otto Hahn]], both proposed as possible namesakes for element 105
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JINR did not propose a name after their first report claiming synthesis of element 105, which would have been the usual practice. This led LBL to believe that JINR did not have enough experimental data to back their claim.<ref>{{Cite encyclopedia|url=https://www.britannica.com/science/dubnium|title=Dubnium {{!}} chemical element|encyclopedia=[[Encyclopedia Britannica]]|access-date=March 25, 2018|language=en|archive-date=March 25, 2018|archive-url=https://web.archive.org/web/20180325110250/https://www.britannica.com/science/dubnium|url-status=live}}</ref> After collecting more data, JINR proposed the name ''bohrium'' (Bo) in honor of the Danish nuclear physicist [[Niels Bohr]], a founder of the theories of [[atomic structure]] and [[Old quantum theory|quantum theory]];<ref>{{Cite book |url=https://books.google.com/books?id=cEkqAAAAMAAJ&q=bohrium |title=Soviet Science Review |date=1972 |publisher=IPC Science and Technology Press |language=en}}</ref> they soon changed their proposal to ''nielsbohrium'' (Ns) to avoid confusion with [[boron]].<ref>{{Cite book |url=https://books.google.com/books?id=GDU7AAAAMAAJ |title=Industries atomiques et spatiales, Volume 16 |date=1972 |location=Switzerland |pages=30–31 |language=fr |access-date=September 8, 2022 |archive-date=December 23, 2022 |archive-url=https://web.archive.org/web/20221223102541/https://books.google.com/books?id=GDU7AAAAMAAJ |url-status=live }}</ref> Another proposed name was ''dubnium''.<ref>{{cite book | url=https://books.google.com/books?id=6GCqk1BSid0C&dq=dubnium&pg=PA59 | isbn=9780851862545 | title=Radiochemistry | year=1972 | publisher=Royal Society of Chemistry | access-date=March 19, 2023 | archive-date=October 8, 2024 | archive-url=https://web.archive.org/web/20241008102036/https://books.google.com/books?id=6GCqk1BSid0C&dq=dubnium&pg=PA59#v=onepage&q=dubnium&f=false | url-status=live }}</ref><ref>{{cite book | url=https://books.google.com/books?id=dI3QAAAAMAAJ&q=dubnium | title=Suomen kemistilehti | year=1971 | publisher=Suomalaisten Kemistien Seura. | access-date=March 19, 2023 | archive-date=October 8, 2024 | archive-url=https://web.archive.org/web/20241008101933/https://books.google.com/books?id=dI3QAAAAMAAJ&q=dubnium | url-status=live }}</ref> When LBL first announced their synthesis of element 105, they proposed that the new element be named ''hahnium'' (Ha) after the German chemist [[Otto Hahn]], the "father of nuclear chemistry", thus creating an [[element naming controversy]].<ref name="FontaniCosta2014">{{cite book|last1=Fontani|first1=M.|last2=Costa|first2=M.|last3=Orna|first3=M. V.|title=The Lost Elements: The Periodic Table's Shadow Side|url=https://books.google.com/books?id=Te1jBAAAQBAJ&pg=PA386|date=2014|publisher=Oxford University Press|isbn=978-0-19-938335-1|page=386|url-status=live|archive-url=https://web.archive.org/web/20180227084247/https://books.google.com/books?id=Te1jBAAAQBAJ&pg=PA386|archive-date=February 27, 2018}}</ref>

In the early 1970s, both teams reported synthesis of the next element, element 106, but did not suggest names.<ref>{{cite book|title=Можно ли сделать золото? Мошенники, обманщики и ученые в истории химических элементов|trans-title=Can one make gold? Swindlers, deceivers and scientists from the history of the chemical elements|language=ru|last=Hoffmann|first=K.|pages=180–181|year=1987|publisher=Nauka}} Translation from {{cite book|title=Kann man Gold machen? Gauner, Gaukler und Gelehrte. Aus der Geschichte der chemischen Elemente|trans-title=Can one make gold? Swindlers, deceivers and scientists. From the history of the chemical elements|language=de|last=Hoffmann|first=K.|year=1979|publisher=Urania}}</ref> JINR suggested establishing an international committee to clarify the discovery criteria. This proposal was accepted in 1974 and a neutral joint group formed.<ref name="1993 response">{{Cite journal|year=1993|title=Responses on the report 'Discovery of the Transfermium elements' followed by reply to the responses by Transfermium Working Group|url=https://www.iupac.org/publications/pac/1993/pdf/6508x1815.pdf|url-status=live|journal=Pure and Applied Chemistry|volume=65|issue=8|pages=1815–1824|doi=10.1351/pac199365081815|archive-url=https://web.archive.org/web/20131125223512/http://www.iupac.org/publications/pac/1993/pdf/6508x1815.pdf|archive-date=25 November 2013|access-date=7 September 2016|last1=Ghiorso|first1=A.|last2=Seaborg|first2=G. T.|author-link2=Glenn T. Seaborg|last3=Oganessian|first3=Yu. Ts.|last4=Zvara|first4=I|last5=Armbruster|first5=P|last6=Hessberger|first6=F. P|last7=Hofmann|first7=S|last8=Leino|first8=M|last9=Munzenberg|first9=G|last10=Reisdorf|first10=W|last11=Schmidt|first11=K.-H|s2cid=95069384|display-authors=3}}</ref> Neither team showed interest in resolving the conflict through a third party, so the leading scientists of LBL—[[Albert Ghiorso]] and [[Glenn Seaborg]]—traveled to Dubna in 1975 and met with the leading scientists of JINR—[[Georgy Flerov]], [[Yuri Oganessian]], and others—to try to resolve the conflict internally and render the neutral joint group unnecessary; after two hours of discussions, this failed.<ref>{{Cite journal|last=Robinson|first=A.|date=2017|title=An Attempt to Solve the Controversies Over Elements 104 and 105: A Meeting in Russia, 23 September 1975|url=http://meetings.aps.org/Meeting/APR17/Session/B10.3|journal=Bulletin of the American Physical Society|volume=62|pages=B10.003|access-date=October 14, 2017|number=1|url-status=live|archive-url=https://web.archive.org/web/20170922194715/http://meetings.aps.org/Meeting/APR17/Session/B10.3|archive-date=September 22, 2017|bibcode=2017APS..APRB10003R}}</ref> The joint neutral group never assembled to assess the claims, and the conflict remained unresolved.<ref name="1993 response" /> In 1979, IUPAC suggested [[systematic element name]]s to be used as placeholders until permanent names were established; under it, element 105 would be ''unnilpentium'', from the Latin roots ''un-'' and ''nil-'' and the Greek root ''pent-'' (meaning "one", "zero", and "five", respectively, the digits of the atomic number). Both teams ignored it as they did not wish to weaken their outstanding claims.<ref>{{Cite journal|last1=Öhrström|first1=L.|last2=Holden|first2=N. E.|year=2016|title=The Three-letter Element Symbols|journal=Chemistry International|volume=38|issue=2|doi=10.1515/ci-2016-0204|doi-access=free}}</ref>

In 1981, the [[Gesellschaft für Schwerionenforschung]] (GSI; ''Society for Heavy Ion Research'') in [[Darmstadt]], [[Hesse]], West Germany, claimed synthesis of element 107; their report came out five years after the first report from JINR but with greater precision, making a more solid claim on discovery.<ref name="1993 report">{{Cite journal|year=1993|title=Discovery of the Transfermium elements|url=http://s3.documentcloud.org/documents/562229/iupac1.pdf |archive-url=https://web.archive.org/web/20160920113229/http://s3.documentcloud.org/documents/562229/iupac1.pdf |archive-date=2016-09-20 |url-status=live|journal=Pure and Applied Chemistry|volume=65|issue=8|pages=1757|doi=10.1351/pac199365081757|access-date=September 7, 2016|last1=Barber|first1=R. C.|last2=Greenwood|first2=N. N.|author-link2=Norman Greenwood|last3=Hrynkiewicz|first3=A. Z.|display-authors=3|last4=Jeannin|first4=Y. P|last5=Lefort|first5=M|last6=Sakai|first6=M|last7=Ulehla|first7=I|last8=Wapstra|first8=A. H|last9=Wilkinson|first9=D. H|s2cid=195819585}}</ref> GSI acknowledged JINR's efforts by suggesting the name ''nielsbohrium'' for the new element.<ref name="1993 response" /> JINR did not suggest a new name for element 105, stating it was more important to determine its discoverers first.<ref name="1993 response" />

{{Location map+ |European Russia |width=250 |float=right|caption=Location of [[Dubna]] within [[European Russia]] |alt= Dubna is located in European Russia.|places=
{{Location map~ |European Russia |lat_deg=56|lat_min=44|lon_deg=37|lon_min=10|position=right|label='''[[Dubna]]'''}}
}}

In 1985, the [[International Union of Pure and Applied Chemistry]] (IUPAC) and the [[International Union of Pure and Applied Physics]] (IUPAP) formed a Transfermium Working Group (TWG) to assess discoveries and establish final names for the controversial elements.<ref name="1993 report" /> The party held meetings with delegates from the three competing institutes; in 1990, they established criteria on recognition of an element, and in 1991, they finished the work on assessing discoveries and disbanded. These results were published in 1993. According to the report, the first definitely successful experiment was the April 1970 LBL experiment, closely followed by the June 1970 JINR experiment, so credit for the discovery of the element should be shared between the two teams.<ref name="1993 report" />

LBL said that the input from JINR was overrated in the review. They claimed JINR was only able to unambiguously demonstrate the synthesis of element 105 a year after they did. JINR and GSI endorsed the report.<ref name="1993 response" />

In 1994, IUPAC published a recommendation on naming the disputed elements. For element 105, they proposed ''joliotium'' (Jl) after the French physicist [[Frédéric Joliot-Curie]], a contributor to the development of nuclear physics and chemistry; this name was originally proposed by the Soviet team for element 102, which by then had long been called [[nobelium]].<ref name="1994 IUPAC">{{Cite journal|year=1994|title=Names and symbols of transfermium elements (IUPAC Recommendations 1994)|url=https://www.iupac.org/publications/pac-2007/1994/pdf/6612x2419.pdf|journal=Pure and Applied Chemistry|volume=66|issue=12|pages=2419–2421|doi=10.1351/pac199466122419|access-date=September 7, 2016|url-status=live|archive-url=https://web.archive.org/web/20170922194905/https://www.iupac.org/publications/pac-2007/1994/pdf/6612x2419.pdf|archive-date=September 22, 2017}}</ref> This recommendation was criticized by the American scientists for several reasons. Firstly, their suggestions were scrambled: the names ''rutherfordium'' and ''hahnium'', originally suggested by Berkeley for elements 104 and 105, were respectively reassigned to elements 106 and 108. Secondly, elements 104 and 105 were given names favored by JINR, despite earlier recognition of LBL as an equal co-discoverer for both of them. Thirdly and most importantly, IUPAC rejected the name ''seaborgium'' for element 106, having just approved a rule that an element could not be named after a living person, even though the 1993 report had given the LBL team the sole credit for its discovery.<ref>{{Cite web|url=http://www2.lbl.gov/Science-Articles/Archive/seaborgium-dispute.html|title=Naming of element 106 disputed by international committee|last=Yarris|first=L.|year=1994|access-date=September 7, 2016|archive-date=July 1, 2016|archive-url=https://web.archive.org/web/20160701203756/http://www2.lbl.gov/Science-Articles/Archive/seaborgium-dispute.html|url-status=live}}</ref>

In 1995, IUPAC abandoned the controversial rule and established a committee of national representatives aimed at finding a compromise. They suggested ''seaborgium'' for element 106 in exchange for the removal of all the other American proposals, except for the established name ''lawrencium'' for element 103. The equally entrenched name ''nobelium'' for element 102 was replaced by ''flerovium'' after Georgy Flerov, following the recognition by the 1993 report that that element had been first synthesized in Dubna. This was rejected by American scientists and the decision was retracted.<ref name="AlbertC2000">{{harvnb|Hoffman|Ghiorso|Seaborg|2000|pp=389–394}}</ref><ref name="Haire" /> The name ''[[flerovium]]'' was later used for element 114.<ref>{{cite journal |last1=Loss |first1=R. D. |last2=Corish |first2=J. |date=2012 |title=Names and symbols of the elements with atomic numbers 114 and 116 (IUPAC Recommendations 2012) |url=https://www.iupac.org/publications/pac/pdf/2012/pdf/8407x1669.pdf |journal=Pure and Applied Chemistry |volume=84 |issue=7 |pages=1669–1672 |doi=10.1351/PAC-REC-11-12-03 |s2cid=96830750 |access-date=21 April 2018 |archive-date=August 3, 2017 |archive-url=https://web.archive.org/web/20170803091051/https://www.iupac.org/publications/pac/pdf/2012/pdf/8407x1669.pdf |url-status=live }}</ref>

In 1996, IUPAC held another meeting, reconsidered all names in hand, and accepted another set of recommendations; it was approved and published in 1997.<ref name="Bera1999">{{Cite journal|last=Bera|first=J. K.|year=1999|title=Names of the Heavier Elements |journal=Resonance|volume=4|issue=3|pages=53–61|doi=10.1007/BF02838724|s2cid=121862853}}</ref> Element 105 was named ''dubnium'' (Db), after [[Dubna]] in Russia, the location of the JINR; the American suggestions were used for elements 102, 103, 104, and 106. The name ''dubnium'' had been used for element 104 in the previous IUPAC recommendation. The American scientists "reluctantly" approved this decision.<ref>{{harvnb|Hoffman|Ghiorso|Seaborg|2000|pp=369–399}}</ref> IUPAC pointed out that the Berkeley laboratory had already been recognized several times, in the naming of [[berkelium]], [[californium]], and [[americium]], and that the acceptance of the names ''rutherfordium'' and ''seaborgium'' for elements 104 and 106 should be offset by recognizing JINR's contributions to the discovery of elements 104, 105, and 106.<ref>{{cite journal | doi=10.1351/pac199769122471|title=Names and symbols of transfermium elements (IUPAC Recommendations 1997) | year=1997 | journal=Pure and Applied Chemistry | volume=69 | pages=2471–2474 | issue=12| doi-access=free }}</ref>

Even after 1997, LBL still sometimes used the name ''hahnium'' for element 105 in their own material, doing so as recently as 2014.<ref>{{cite web |url=https://www2.lbl.gov/abc/marsh-nuclei/images/table_sig.jpg |title=Periodic Table of the Elements |last= |first= |date=1999 |website=lbl.gov |publisher=Lawrence Berkeley National Laboratory |access-date=6 December 2022 |quote= |archive-date=April 21, 2021 |archive-url=https://web.archive.org/web/20210421141406/https://www2.lbl.gov/abc/marsh-nuclei/images/table_sig.jpg |url-status=live }}</ref><ref>{{cite thesis |last=Wilk |first=P. A. |date=2001 |title=Properties of Group Five and Group Seven transactinium elements |url=https://www.osti.gov/biblio/785268 |type=PhD |chapter= |publisher=University of California, Berkeley |doi=10.2172/785268 |osti=785268 |docket= |oclc= |access-date=6 December 2022 |archive-date=October 31, 2022 |archive-url=https://web.archive.org/web/20221031014849/https://www.osti.gov/biblio/785268 |url-status=live }}</ref><ref>{{cite web |url=https://alumni.berkeley.edu/california-magazine/spring-2014-branding/branding-elements-berkeley-stakes-its-claims-periodic-table |title=Branding the Elements: Berkeley Stakes its Claims on the Periodic Table |last=Buhler |first=Brendan |date=2014 |website=alumni.berkeley.edu |publisher=Cal Alumni Association |access-date=6 December 2022 |quote=Poor element 105 has had five different names—Berkeley partisans still call it hahnium. |archive-date=October 31, 2022 |archive-url=https://web.archive.org/web/20221031014850/https://alumni.berkeley.edu/california-magazine/spring-2014-branding/branding-elements-berkeley-stakes-its-claims-periodic-table |url-status=live }}</ref><ref>{{Cite tweet |user=BerkeleyLab |number=420831560573521921 |title=#16elements from Berkeley Lab: mendelevium, nobelium, lawrencium, rutherfordium, hahnium, seaborgium.}}</ref> However, the problem was resolved in the literature as Jens Volker Kratz, editor of ''Radiochimica Acta'', refused to accept papers not using the 1997 IUPAC nomenclature.<ref>{{cite journal |last1=Armbruster |first1=Peter |last2=Münzenberg |first2=Gottfried |date=2012 |title=An experimental paradigm opening the world of superheavy elements |url=https://link.springer.com/article/10.1140/epjh/e2012-20046-7 |journal=The European Physical Journal H |volume=37 |issue=2 |pages=237–309 |doi=10.1140/epjh/e2012-20046-7 |bibcode=2012EPJH...37..237A |s2cid=123446987 |access-date=6 December 2022 |archive-date=December 6, 2022 |archive-url=https://web.archive.org/web/20221206084057/https://link.springer.com/article/10.1140/epjh/e2012-20046-7 |url-status=live }}</ref>
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