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'''Oganesson''' is a [[synthetic element|synthetic chemical element]]; it has [[Chemical symbol|symbol]] '''Og''' and [[atomic number]] 118. It was first synthesized in 2002 at the [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], near Moscow, Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by the [[IUPAC/IUPAP Joint Working Party|Joint Working Party]] of the international scientific bodies [[IUPAC]] and [[IUPAP]]. It was formally named on 28 November 2016.<ref name="IUPAC-20161130">{{cite news |date=30 November 2016 |title=IUPAC Announces the Names of the Elements 113, 115, 117, and 118 |work=[[IUPAC]] |url=https://iupac.org/iupac-announces-the-names-of-the-elements-113-115-117-and-118/ |url-status=live |access-date=1 December 2015 |archive-url=https://web.archive.org/web/20161130185117/https://iupac.org/iupac-announces-the-names-of-the-elements-113-115-117-and-118/ |archive-date=30 November 2016}}</ref><ref name="NYT-20161201">{{cite news |last=St. Fleur |first=Nicholas |date=1 December 2016 |title=Four New Names Officially Added to the Periodic Table of Elements |work=[[The New York Times]] |url=https://www.nytimes.com/2016/12/01/science/periodic-table-new-elements.html |url-access=subscription |access-date=1 December 2016}}</ref> The name honors the nuclear physicist [[Yuri Oganessian]], who played a leading role in the discovery of the heaviest elements in the periodic table. It is one of only two elements named after a person who was alive at the time of naming, the other being [[seaborgium]], and the only element whose [[eponym]] is alive {{As of|lc=y|2024}}.<ref name="IUPAC-June2016">{{cite web |date=8 June 2016 |title=IUPAC Is Naming The Four New Elements Nihonium, Moscovium, Tennessine, And Oganesson |url=https://iupac.org/iupac-is-naming-the-four-new-elements-nihonium-moscovium-tennessine-and-oganesson/ |url-status=live |archive-url=https://web.archive.org/web/20160608140005/https://iupac.org/iupac-is-naming-the-four-new-elements-nihonium-moscovium-tennessine-and-oganesson/ |archive-date=8 June 2016 |publisher=[[IUPAC]]}}</ref>{{efn|The names [[einsteinium]] and [[fermium]] for elements 99 and 100 were proposed when their namesakes ([[Albert Einstein]] and [[Enrico Fermi]], respectively) were still alive, but were not made official until Einstein and Fermi had died.{{sfn|Hoffman|Ghiorso|Seaborg|2000|pp=187–189}}}}

Oganesson has the highest atomic number and highest [[atomic mass]] of all [[List of chemical elements|known elements]] {{As of|lc=y|2024}}. On the periodic table of the elements it is a [[p-block]] element, a member of [[noble gas|group 18]] and the last member of [[period 7]]. Its only known isotope, [[isotopes of oganesson|oganesson-294]], is highly [[radioactive decay|radioactive]], with a half-life of 0.7 ms and, {{as of|2020|lc=y|post=,}} only five atoms have been successfully produced.<ref name="smits2020">{{cite journal |last1=Smits |first1=Odile R. |last2=Mewes |first2=Jan-Michael |last3=Jerabek |first3=Paul |last4=Schwerdtfeger |first4=Peter |date=2020 |title=Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas |journal=Angewandte Chemie International Edition |volume=59 |issue=52 |pages=23636–23640 |doi=10.1002/anie.202011976 |doi-access=free |pmid=32959952 |pmc=7814676 }}</ref> This has so far prevented any experimental studies of its chemistry. Because of [[relativistic quantum chemistry|relativistic effects]], theoretical studies predict that it would be a [[solid]] at [[Standard temperature and pressure|room temperature]], and significantly reactive,<ref name="Nash2005"/><ref name="smits2020"/> unlike the other members of group 18 (the [[noble gas]]es).

==Introduction==
{{Excerpt|Superheavy element|Introduction|subsections=yes}}

==History==
{{see also|Timeline of chemical element discoveries}}

=== Early speculation ===
The possibility of a seventh [[noble gas]], after [[helium]], [[neon]], [[argon]], [[krypton]], [[xenon]], and [[radon]], was considered almost as soon as the noble gas group was discovered. Danish chemist [[Hans Peter Jørgen Julius Thomsen]] predicted in April 1895, the year after the discovery of argon, that there was a whole series of chemically inert gases similar to argon that would bridge the [[halogen]] and [[alkali metal]] groups: he expected that the seventh of this series would end a 32-element period which contained [[thorium]] and [[uranium]] and have an atomic weight of 292, close to the 294 now known for the first and only confirmed isotope of oganesson.{{sfn|Kragh|2018|p=6}} Danish physicist [[Niels Bohr]] noted in 1922 that this seventh noble gas should have atomic number 118 and predicted its electronic structure as 2, 8, 18, 32, 32, 18, 8, matching modern predictions.<ref name="leach">{{cite web |url=https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?PT_id=285 |title=The INTERNET Database of Periodic Tables |author=Leach, Mark R. |access-date=8 July 2016}}</ref> Following this, German chemist [[Aristid von Grosse]] wrote an article in 1965 predicting the likely properties of element 118.<ref name="60s"/> It was 107 years from Thomsen's prediction before oganesson was successfully synthesized, although its chemical properties have not been investigated to determine if it behaves as the heavier [[congener (chemistry)|congener]] of radon.{{Fricke1975}} In a 1975 article, American chemist [[Kenneth Pitzer]] suggested that element 118 should be a [[gas]] or [[Volatility (chemistry)|volatile]] [[liquid]] due to [[Relativistic quantum chemistry|relativistic effects]].<ref name="Pitzer">{{cite journal |title=Are elements 112, 114, and 118 relatively inert gases? |first=Kenneth |last=Pitzer |author-link=Kenneth Pitzer |journal=[[The Journal of Chemical Physics]] |issue=63 |volume=2 |year=1975 |pages=1032–1033|doi=10.1063/1.431398 |url=https://escholarship.org/uc/item/2qw742ss }}</ref>

===Unconfirmed discovery claims===
In late 1998, Polish physicist [[Robert Smolańczuk]] published calculations on the fusion of atomic nuclei towards the synthesis of [[superheavy element|superheavy atoms]], including oganesson.<ref name="Smolanczuk">{{cite journal|author=Smolanczuk, R.|journal=Physical Review C|volume=59|issue=5|date=1999|title=Production mechanism of superheavy nuclei in cold fusion reactions|pages=2634–2639|doi=10.1103/PhysRevC.59.2634|bibcode = 1999PhRvC..59.2634S}}</ref> His calculations suggested that it might be possible to make element 118 by fusing [[lead]] with [[krypton]] under carefully controlled conditions, and that the fusion probability ([[cross section (physics)|cross section]]) of that reaction would be close to the lead–[[chromium]] reaction that had produced element 106, [[seaborgium]]. This contradicted predictions that the cross sections for reactions with lead or [[bismuth]] targets would go down exponentially as the atomic number of the resulting elements increased.<ref name="Smolanczuk"/>

In 1999, researchers at [[Lawrence Berkeley National Laboratory]] made use of these predictions and announced the discovery of elements 118 and [[livermorium|116]], in a paper published in ''[[Physical Review Letters]]'',<ref>{{cite journal|last=Ninov|first=Viktor|title=Observation of Superheavy Nuclei Produced in the Reaction of <sup>86</sup>Kr with <sup>208</sup>Pb|journal=[[Physical Review Letters]]|volume=83|pages=1104–1107|date=1999|doi=10.1103/PhysRevLett.83.1104|bibcode=1999PhRvL..83.1104N|issue=6|url=https://zenodo.org/record/1233919}} {{Retraction|doi=10.1103/PhysRevLett.89.039901|intentional=yes}}</ref> and very soon after the results were reported in ''[[Science (journal)|Science]]''.<ref>{{cite journal|author=Service, R. F.|journal=Science|date=1999|volume=284|page=1751|doi=10.1126/science.284.5421.1751|title=Berkeley Crew Bags Element 118|issue=5421|s2cid=220094113}}</ref> The researchers reported that they had performed the [[nuclear reaction|reaction]]

:{{Nuclide|link=yes|Lead|208}} + {{Nuclide|link=yes|Krypton|86}} → {{Nuclide|Oganesson|293}} + {{SubatomicParticle|link=yes|Neutron}}.

In 2001, they published a retraction after researchers at other laboratories were unable to duplicate the results and the Berkeley lab could not duplicate them either.<ref>{{cite news |author=Public Affairs Department, Lawrence Berkeley Laboratory |date=21 July 2001 |title=Results of element 118 experiment retracted |url=https://enews.lbl.gov/Science-Articles/Archive/118-retraction.html |url-status=dead |access-date=18 January 2008 |archive-url=https://web.archive.org/web/20080129191344/https://enews.lbl.gov/Science-Articles/Archive/118-retraction.html |archive-date=29 January 2008}}</ref> In June 2002, the director of the lab announced that the original claim of the discovery of these two elements had been based on data fabricated by principal author [[Victor Ninov]].<ref>{{cite journal|pages=728–729|title=Misconduct: The stars who fell to Earth|journal=[[Nature (journal)|Nature]]|volume=420|doi=10.1038/420728a|date=2002|pmid=12490902|last=Dalton|first=R.|issue=6917|bibcode = 2002Natur.420..728D |s2cid=4398009}}</ref><ref>{{Cite web |date=2001-08-02 |title=Element 118 disappears two years after it was discovered |url=https://physicsworld.com/a/element-118-disappears-two-years-after-it-was-discovered/ |access-date=2 April 2012 |website=Physics World |language=en-GB}}</ref> Newer experimental results and theoretical predictions have confirmed the exponential decrease in cross sections with lead and bismuth targets as the atomic number of the resulting nuclide increases.{{sfn|Zagrebaev|Karpov|Greiner|2013}}

===Discovery reports===
[[File:Oganesson-294 nuclear.svg|thumb|upright=0.9|alt=Schematic diagram of oganesson-294 alpha decay, with a half-life of 0.89&nbsp;ms and a decay energy of 11.65&nbsp;MeV. The resulting livermorium-290 decays by alpha decay, with a half-life of 10.0&nbsp;ms and a decay energy of 10.80&nbsp;MeV, to flerovium-286. Flerovium-286 has a half-life of 0.16&nbsp;s and a decay energy of 10.16&nbsp;MeV, and undergoes alpha decay to copernicium-282 with a 0.7 rate of spontaneous fission. Copernicium-282 itself has a half-life of only 1.9&nbsp;ms and has a 1.0 rate of spontaneous fission.|[[Radioactive decay]] pathway of the [[isotope]] oganesson-294.<ref name="synthesis-118-116"/> The [[decay energy]] and average [[half-life]] are given for the [[parent isotope]] and each [[daughter isotope]]. The fraction of atoms undergoing [[spontaneous fission]] (SF) is given in green.]]

The first genuine decay of atoms of oganesson was observed in 2002 at the [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], Russia, by a joint team of Russian and American scientists. Headed by [[Yuri Oganessian]], a Russian nuclear physicist of Armenian ethnicity, the team included American scientists from the [[Lawrence Livermore National Laboratory]] in California.<ref name="pp2002">{{cite journal|author=Oganessian, Yu. T.|display-authors=etal|title=Results from the first {{chem|249|Cf}}+{{chem|48|Ca}} experiment|url=https://www.jinr.ru/publish/Preprints/2002/287(D7-2002-287)e.pdf|journal=JINR Communication|date=2002|access-date=13 June 2009|archive-date=13 December 2004|archive-url=https://web.archive.org/web/20041213100709/https://www.jinr.ru/publish/Preprints/2002/287%28D7-2002-287%29e.pdf|url-status=dead}}</ref> The discovery was not announced immediately, because the decay energy of <sup>294</sup>Og matched that of [[isotopes of polonium|<sup>212m</sup>Po]], a common impurity produced in fusion reactions aimed at producing superheavy elements, and thus announcement was delayed until after a 2005 confirmatory experiment aimed at producing more oganesson atoms.<ref name="Moody"/> The 2005 experiment used a different beam energy (251&nbsp;MeV instead of 245&nbsp;MeV) and target thickness (0.34&nbsp;mg/cm<sup>2</sup> instead of 0.23&nbsp;mg/cm<sup>2</sup>).<ref name="synthesis-118-116"/> On 9 October 2006, the researchers announced<ref name="synthesis-118-116"/> that they had indirectly detected a total of three (possibly four) nuclei of oganesson-294 (one or two in 2002<ref>{{cite web|url=https://159.93.28.88/linkc/118/anno.html |title=Element 118: results from the first {{SimpleNuclide|Californium|249}} + {{SimpleNuclide|Calcium|48}} experiment |author=Oganessian, Yu. T. |display-authors=etal |publisher=Communication of the Joint Institute for Nuclear Research |date=2002 |url-status=dead |archive-url=https://web.archive.org/web/20110722060249/https://159.93.28.88/linkc/118/anno.html |archive-date=22 July 2011 }}</ref> and two more in 2005) produced via collisions of [[californium]]-249 atoms and [[calcium-48]] ions.<ref>{{cite news|title=Livermore scientists team with Russia to discover element 118|url=https://www.llnl.gov/news/newsreleases/2006/NR-06-10-03.html|publisher=Livermore press release|date=3 December 2006|access-date=18 January 2008|archive-url=https://web.archive.org/web/20111017105348/https://www.llnl.gov/news/newsreleases/2006/NR-06-10-03.html|archive-date=17 October 2011|url-status=dead}}</ref><ref>{{cite journal|author=Oganessian, Yu. T.|title=Synthesis and decay properties of superheavy elements|journal=Pure Appl. Chem.|volume=78|pages=889–904|doi=10.1351/pac200678050889|date=2006|issue=5|s2cid=55782333|doi-access=free}}</ref><ref>{{cite journal|title=Heaviest element made – again|journal=Nature News|date=2006|doi=10.1038/news061016-4|author= Sanderson, K.|s2cid=121148847}}</ref><ref>{{cite web|author=Schewe, P. |author2=Stein, B. |name-list-style=amp |title=Elements 116 and 118 Are Discovered |work=Physics News Update |publisher=[[American Institute of Physics]] |date=17 October 2006 |url=https://www.aip.org/pnu/2006/797.html |access-date=18 January 2008 |url-status=dead |archive-url=https://web.archive.org/web/20120101144201/https://www.aip.org/pnu/2006/797.html |archive-date= 1 January 2012 }}</ref><ref>{{cite news|url=https://www.washingtonpost.com/wp-dyn/content/article/2006/10/16/AR2006101601083.html|title=Scientists Announce Creation of Atomic Element, the Heaviest Yet|newspaper=The Washington Post|author=Weiss, R.|date=17 October 2006|access-date=18 January 2008}}</ref>

:{{nuclide|link=yes|Californium|249}} + {{nuclide|link=yes|Calcium|48}} → {{nuclide|link=yes|Oganesson|294}} + 3 {{SubatomicParticle|link=yes|Neutron}}.

In 2011, [[IUPAC]] evaluated the 2006 results of the Dubna–Livermore collaboration and concluded: "The three events reported for the ''Z'' = 118 isotope have very good internal
redundancy but with no anchor to known nuclei do not satisfy the criteria for discovery".<ref>{{cite journal|doi=10.1351/PAC-REP-10-05-01|title=Discovery of the elements with atomic numbers greater than or equal to 113 (IUPAC Technical Report)|date=2011|last1=Barber|first1=Robert C.|last2=Karol|first2=Paul J.|last3=Nakahara|first3=Hiromichi|last4=Vardaci|first4=Emanuele|last5=Vogt|first5=Erich W.|journal=Pure and Applied Chemistry|page=1|volume=83|issue=7|doi-access=free}}</ref>

Because of the very small [[fusion reaction]] probability (the fusion [[nuclear cross section|cross section]] is {{gaps|~|0.3–0.6|u=[[Barn (unit)|pb]]}} or {{val|p=(|3|end=–6)|e=-41|u=m2}}) the experiment took four months and involved a beam dose of {{val|2.5|e=19}} [[calcium]] ions that had to be shot at the [[californium]] target to produce the first recorded event believed to be the synthesis of oganesson.<ref name="webelements">{{cite web|url=https://www.webelements.com/oganesson/|title=Oganesson|publisher=WebElements Periodic Table|access-date=19 August 2019}}</ref> Nevertheless, researchers were highly confident that the results were not a [[false positive]], since the chance that the detections were random events was estimated to be less than one part in {{val|100000}}.<ref>{{cite journal|quote="I would say we're very confident."|url=https://pubs.acs.org/cen/news/84/i43/8443element118.html|title=Element 118 Detected, With Confidence|journal=Chemical & Engineering News|date=17 October 2006|access-date=18 January 2008|author=Jacoby, Mitch |volume=84|issue=43|pages=11|doi=10.1021/cen-v084n043.p011}}</ref>

In the experiments, the alpha-decay of three atoms of oganesson was observed. A fourth decay by direct [[spontaneous fission]] was also proposed. A [[half-life]] of 0.89&nbsp;ms was calculated: {{chem|294|Og}} decays into {{chem|link=Isotopes of livermorium#Livermorium-290|290|Lv}} by [[alpha decay]]. Since there were only three nuclei, the half-life derived from observed lifetimes has a large uncertainty: {{val|0.89|+1.07|-0.31|u=ms}}.<ref name="synthesis-118-116"/>

:{{nuclide|Oganesson|294}} → {{nuclide|livermorium|290}} + {{nuclide|link=yes|helium|4}}

The identification of the {{chem|294|Og}} nuclei was verified by separately creating the putative [[decay product|daughter nucleus]] {{chem|290|Lv}} directly by means of a bombardment of {{chem|link=curium-245|245|Cm}} with {{chem|link=calcium-48|48|Ca}} ions,

:{{nuclide|Curium|245}} + {{nuclide|Calcium|48}} → {{nuclide|livermorium|290}} + 3 {{SubatomicParticle|link=yes|Neutron}},

and checking that the {{chem|290|Lv}} decay matched the [[decay chain]] of the {{chem|294|Og}} nuclei.<ref name="synthesis-118-116"/> The daughter nucleus {{chem|290|Lv}} is very unstable, decaying with a lifetime of 14 milliseconds into {{chem|link=flerovium-286|286|Fl}}, which may experience either spontaneous fission or alpha decay into {{chem|link=copernicium-282|282|Cn}}, which will undergo spontaneous fission.<ref name="synthesis-118-116"/>

===Confirmation===
In December 2015, the [[IUPAC/IUPAP Joint Working Party|Joint Working Party]] of international scientific bodies [[International Union of Pure and Applied Chemistry]] (IUPAC) and [[International Union of Pure and Applied Physics]] (IUPAP) recognized the element's discovery and assigned the priority of the discovery to the Dubna–Livermore collaboration.<ref>[https://www.iupac.org/news/news-detail/article/discovery-and-assignment-of-elements-with-atomic-numbers-113-115-117-and-118.html Discovery and Assignment of Elements with Atomic Numbers 113, 115, 117 and 118]. IUPAC (30 December 2015)</ref> This was on account of two 2009 and 2010 confirmations of the properties of the granddaughter of <sup>294</sup>Og, <sup>286</sup>Fl, at the [[Lawrence Berkeley National Laboratory]], as well as the observation of another consistent decay chain of <sup>294</sup>Og by the Dubna group in 2012. The goal of that experiment had been the synthesis of <sup>294</sup>Ts via the reaction <sup>249</sup>Bk(<sup>48</sup>Ca,3n), but the short half-life of <sup>249</sup>Bk resulted in a significant quantity of the target having decayed to <sup>249</sup>Cf, resulting in the synthesis of oganesson instead of [[tennessine]].<ref>{{cite journal |last1=Karol |first1=Paul J. |last2=Barber |first2=Robert C. |last3=Sherrill |first3=Bradley M. |last4=Vardaci |first4=Emanuele |last5=Yamazaki |first5=Toshimitsu |date=29 December 2015 |title=Discovery of the element with atomic number Z = 118 completing the 7th row of the periodic table (IUPAC Technical Report) |journal=Pure Appl. Chem. |volume=88 |issue=1–2 |pages=155–160 |doi=10.1515/pac-2015-0501 |s2cid=102228960 |url=https://zenodo.org/record/6472870 |doi-access=free }}</ref>

From 1 October 2015 to 6 April 2016, the Dubna team performed a similar experiment with <sup>48</sup>Ca projectiles aimed at a mixed-isotope californium target containing <sup>249</sup>Cf, <sup>250</sup>Cf, and <sup>251</sup>Cf, with the aim of producing the heavier oganesson isotopes <sup>295</sup>Og and <sup>296</sup>Og. Two beam energies at 252&nbsp;MeV and 258&nbsp;MeV were used. Only one atom was seen at the lower beam energy, whose decay chain fitted the previously known one of <sup>294</sup>Og (terminating with spontaneous fission of <sup>286</sup>Fl), and none were seen at the higher beam energy. The experiment was then halted, as the glue from the sector frames covered the target and blocked evaporation residues from escaping to the detectors.<ref name="Dubna2016">{{cite conference |title=Results from the Recent Study of the <sup>249–251</sup>Cf + <sup>48</sup>Ca Reactions |first1=A. A. |last1=Voinov |first2=Yu. Ts |last2=Oganessian |first3=F. Sh. |last3=Abdullin |first4=N. T. |last4=Brewer |first5=S. N. |last5=Dmitriev |first6=R. K. |last6=Grzywacz |first7=J. H. |last7=Hamilton |first8=M. G. |last8=Itkis |first9=K. |last9=Miernik |first10=A. N. |last10=Polyakov |first11=J. B. |last11=Roberto |first12=K. P. |last12=Rykaczewski |first13=A. V. |last13=Sabelnikov |first14=R. N. |last14=Sagaidak |first15=I. V. |last15=Shriokovsky |first16=M. V. |last16=Shumeiko |first17=M. A. |last17=Stoyer |first18=V. G. |last18=Subbotin |first19=A. M. |last19=Sukhov |first20=Yu. S. |last20=Tsyganov |first21=V. K. |last21=Utyonkov |first22=G. K. |last22=Vostokin |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=219–223 |isbn=9789813226555}}</ref> The production of <sup>293</sup>Og and its daughter <sup>289</sup>Lv, as well as the even heavier isotope <sup>297</sup>Og, is also possible using this reaction. The isotopes <sup>295</sup>Og and <sup>296</sup>Og may also be produced in the fusion of <sup>248</sup>Cm with <sup>50</sup>Ti projectiles.<ref name="Dubna2016"/><ref>{{cite news |last=Sychev |first=Vladimir |date=8 February 2017 |title=Юрий Оганесян: мы хотим узнать, где кончается таблица Менделеева | trans-title=Yuri Oganessian: we want to know where the Mendeleev table ends |url=https://ria.ru/interview/20170208/1487412085.html |language=ru |access-date=31 March 2017 |work=[[RIA Novosti]]}}</ref><ref>
{{cite web |url=https://cyclotron.tamu.edu/she2015/assets/pdfs/presentations/Roberto_SHE_2015_TAMU.pdf |title=Actinide Targets for Super-Heavy Element Research |last=Roberto |first=J. B. |date=31 March 2015 |website=cyclotron.tamu.edu |publisher=Texas A & M University |access-date=28 April 2017}}</ref> A search beginning in summer 2016 at RIKEN for <sup>295</sup>Og in the 3n channel of this reaction was unsuccessful, though the study is planned to resume; a detailed analysis and cross section limit were not provided. These heavier and likely more stable isotopes may be useful in probing the chemistry of oganesson.<ref name="conseil">{{cite conference |last=Hauschild |first=K. |title=Superheavy nuclei at RIKEN, Dubna, and JYFL |date=26 June 2019 |conference=Conseil Scientifique de l'IN2P3 |url=https://in2p3.cnrs.fr/sites/institut_in2p3/files/page/2019-07/6-Pres-HAUSCHILD_-compresse%CC%81.pdf |access-date=31 July 2019}}</ref><ref name="conseil2">{{cite conference |last=Hauschild |first=K. |title=Heavy nuclei at RIKEN, Dubna, and JYFL |date=2019 |conference=Conseil Scientifique de l'IN2P3 |url=https://in2p3.cnrs.fr/sites/institut_in2p3/files/page/2019-07/6-Doc-HAUSCHILD-comp.pdf |access-date=1 August 2019}}</ref>

===Naming===
[[File:Yuri Oganessian 2017 stamp of Armenia.jpg|thumb|right|upright=1.1|Element 118 was named after [[Yuri Oganessian]], a pioneer in the discovery of [[synthetic element]]s, with the name ''oganesson'' (Og). Oganessian and the decay chain of oganesson-294 were pictured on a stamp of Armenia issued on 28 December 2017.]]
Using [[Mendeleev's predicted elements|Mendeleev's nomenclature for unnamed and undiscovered elements]], oganesson is sometimes known as ''eka-radon'' (until the 1960s as ''eka-emanation'', emanation being the old name for [[radon]]).<ref name="60s"/> In 1979, IUPAC assigned the [[systematic element name|systematic]] [[placeholder name]] ''ununoctium'' to the undiscovered element, with the corresponding symbol of ''Uuo'',<ref name="iupac">{{cite journal|author=Chatt, J.|journal=Pure Appl. Chem.|date=1979|volume=51|pages=381–384|title=Recommendations for the Naming of Elements of Atomic Numbers Greater than 100|doi=10.1351/pac197951020381|issue=2|doi-access=free}}</ref> and recommended that it be used until after confirmed discovery of the element.<ref>{{cite journal|title=Atomic weights of the elements 2005 (IUPAC Technical Report)|journal=Pure Appl. Chem.|date=2006|volume=78|issue=11|pages=2051–2066| doi=10.1351/pac200678112051| author=Wieser, M.E.|s2cid=94552853|doi-access=free}}</ref> Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations were mostly ignored among scientists in the field, who called it "element 118", with the symbol of ''E118'', ''(118)'', or simply ''118''.<ref name="Haire"/>

Before the retraction in 2001, the researchers from Berkeley had intended to name the element ''ghiorsium'' (''Gh''), after [[Albert Ghiorso]] (a leading member of the research team).<ref>{{cite web|title=Discovery of New Elements Makes Front Page News|url=https://lbl.gov/Science-Articles/Research-Review/Magazine/1999/departments/breaking_news.shtml|publisher=Berkeley Lab Research Review Summer 1999|date=1999|access-date=18 January 2008}}</ref>

The Russian discoverers reported their synthesis in 2006. According to IUPAC recommendations, the discoverers of a new element have the right to suggest a name.<ref>
{{cite journal
|last=Koppenol |first=W. H.
|date=2002
|title=Naming of new elements (IUPAC Recommendations 2002)
|url=https://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf
|journal=[[Pure and Applied Chemistry]]
|volume=74 |page=787 |issue=5
|doi=10.1351/pac200274050787
|s2cid=95859397
}}</ref> In 2007, the head of the Russian institute stated the team were considering two names for the new element: ''flyorium'', in honor of [[Georgy Flyorov]], the founder of the research laboratory in Dubna; and ''moskovium'', in recognition of the [[Moscow Oblast]] where Dubna is located.<ref>{{cite web|url=https://news.rin.ru/eng/news/9886/9/6/|title=New chemical elements discovered in Russia's Science City|date=12 February 2007|access-date=9 February 2008}}</ref> He also stated that although the element was discovered as an American collaboration, who provided the californium target, the element should rightly be named in honor of Russia since the [[Flyorov Laboratory of Nuclear Reactions]] at JINR was the only facility in the world which could achieve this result.<ref>{{cite web|last=Yemel'yanova|language=ru|first=Asya|date=17 December 2006|url=https://www.vesti.ru/doc.html?id=113947|title=118-й элемент назовут по-русски (118th element will be named in Russian)|publisher=vesti.ru|access-date=18 January 2008|archive-date=25 December 2008|archive-url=https://web.archive.org/web/20081225102337/https://www.vesti.ru/doc.html?id=113947|url-status=dead}}</ref> These names were later suggested for [[flerovium|element 114]] (flerovium) and [[livermorium|element 116]] (moscovium).<ref>{{cite web|publisher=rian.ru|date=2011|access-date=8 May 2011|url=https://ria.ru/science/20110326/358081075.html|title=Российские физики предложат назвать 116 химический элемент московием (Russian Physicians Will Suggest to Name Element 116 Moscovium)|language=ru}}</ref> Flerovium became the name of element 114; the final name proposed for element 116 was instead ''livermorium'',<ref name="IUPAC">{{cite web|title=News: Start of the Name Approval Process for the Elements of Atomic Number 114 and 116 |url=https://www.iupac.org/news/news-detail/article/start-of-the-name-approval-process-for-the-elements-of-atomic-number-114-and-116.html |work=International Union of Pure and Applied Chemistry |access-date=2 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20140823092056/https://www.iupac.org/news/news-detail/article/start-of-the-name-approval-process-for-the-elements-of-atomic-number-114-and-116.html |archive-date=23 August 2014 }}</ref> with ''moscovium'' later being proposed and accepted for [[moscovium|element 115]] instead.<ref name="IUPAC-June2016"/>

Traditionally, the names of all [[noble gas]]es end in "-on", with the exception of [[helium]], which was not known to be a noble gas when discovered. The IUPAC guidelines valid at the moment of the discovery approval however required ''all'' new elements be named with the ending "-ium", even if they turned out to be [[halogen]]s (traditionally ending in "-ine") or noble gases (traditionally ending in "-on").<ref name="Koppenol">{{cite journal |doi=10.1351/pac200274050787 |url=https://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf |title=Naming of new elements (IUPAC Recommendations 2002) |date=2002 |last=Koppenol |first=W. H. |journal=Pure and Applied Chemistry |volume=74 |pages=787–791 |issue=5 |s2cid=95859397 }}</ref> While the provisional name ununoctium followed this convention, a new IUPAC recommendation published in 2016 recommended using the "-on" ending for new [[group 18 element]]s, regardless of whether they turn out to have the chemical properties of a noble gas.<ref>{{cite journal|title = How to name new chemical elements (IUPAC Recommendations 2016) | journal = Pure and Applied Chemistry | volume = 88 | issue = 4 | pages = 401–405 | doi = 10.1515/pac-2015-0802| year = 2016 | last1 = Koppenol | first1 = Willem H. | last2 = Corish | first2 = John | last3 = García-Martínez | first3 = Javier | last4 = Meija | first4 = Juris | last5 = Reedijk | first5 = Jan | hdl = 10045/55935 | s2cid = 102245448 | url = https://doc.rero.ch/record/325660/files/pac-2015-0802.pdf | hdl-access = free }}</ref>

The scientists involved in the discovery of element 118, as well as those of [[tennessine|117]] and [[moscovium|115]], held a conference call on 23 March 2016 to decide their names. Element 118 was the last to be decided upon; after Oganessian was asked to leave the call, the remaining scientists unanimously decided to have the element "oganesson" after him. Oganessian was a pioneer in superheavy element research for sixty years reaching back to the field's foundation: his team and his proposed techniques had led directly to the synthesis of elements [[bohrium|107]] through 118. Mark Stoyer, a nuclear chemist at the LLNL, later recalled, "We had intended to propose that name from Livermore, and things kind of got proposed at the same time from multiple places. I don't know if we can claim that we actually proposed the name, but we had intended it."<ref name="chemistryworld">{{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|newspaper=Chemistry World|access-date=3 December 2016}}</ref>

In internal discussions, IUPAC asked the JINR if they wanted the element to be spelled "oganeson" to match the Russian spelling more closely. Oganessian and the JINR refused this offer, citing the Soviet-era practice of transliterating names into the Latin alphabet under the rules of the French language ("Oganessian" is such a transliteration) and arguing that "oganesson" would be easier to link to the person.<ref name="Og19"/>{{efn|In Russian, Oganessian's name is spelled Оганесян {{IPA|ru|ˈɐgənʲɪˈsʲan|}}; the transliteration in accordance with the rules of the English language would be ''Oganesyan'', with one s. Similarly, the Russian name for the element is оганесон, letter-for-letter ''oganeson''.
Oganessian is the Russified version of the Armenian last name [[Hovhannisyan]] ({{langx|hy|Հովհաննիսյան}} {{IPA-hy|hɔvhɑnnisˈjɑn|}}).
It means "son of [[Hovhannes]]", i.e., "son of John".
It is one of the [[List of most common surnames in Asia#Armenia|most common surnames in Armenia]].}}
In June 2016, IUPAC announced that the discoverers planned to give the element the name ''oganesson'' (symbol: ''Og''). The name became official on 28 November 2016.<ref name="IUPAC-June2016"/> In 2017, Oganessian commented on the naming:<ref name="newscientist"/>

{{blockquote|For me, it is an honour. The discovery of element 118 was by scientists at the Joint Institute for Nuclear Research in Russia and at the Lawrence Livermore National Laboratory in the US, and it was my colleagues who proposed the name oganesson. My children and grandchildren have been living in the US for decades, but my daughter wrote to me to say that she did not sleep the night she heard because she was crying.<ref name="newscientist">{{cite news |last=Gray |first=Richard |date=11 April 2017 |title=Mr Element 118: The only living person on the periodic table |url=https://www.newscientist.com/article/mg23431210-600-up-and-atom-breaking-the-periodic-table/ |work=[[New Scientist]] |access-date=26 April 2017}}</ref>|Yuri Oganessian}}

The naming ceremony for moscovium, tennessine, and oganesson was held on 2 March 2017 at the [[Russian Academy of Sciences]] in Moscow.<ref>{{cite web |url=https://www.jinr.ru/posts/at-the-inauguration-ceremony-of-the-new-elements-of-the-periodic-table-of-d-i-mendeleev/ |title=At the inauguration ceremony of the new elements of the Periodic table of D.I. Mendeleev |last=Fedorova |first=Vera |date=3 March 2017 |website=jinr.ru |publisher=[[Joint Institute for Nuclear Research]] |access-date=4 February 2018}}</ref>

In a 2019 interview, when asked what it was like to see his name in the periodic table next to [[Albert Einstein|Einstein]], [[Dmitry Mendeleev|Mendeleev]], [[Curie family|the Curies]], and [[Ernest Rutherford|Rutherford]], Oganessian responded:<ref name="Og19">{{cite magazine|last1=Tarasevich|first1=Grigoriy|last2=Lapenko|first2=Igor|date=2019|title=Юрий Оганесян о тайнах ядра, новых элементах и смысле жизни|trans-title=Yuri Oganessian about the secret of the nucleus, new elements and the meaning of life|journal=Kot Shryodingyera|language=ru|publisher=Direktsiya Festivalya Nauki|issue=Special|pages=22}}</ref>

{{blockquote|Not like much! You see, not like much. It is customary in science to name something new after its discoverer. It's just that there are few elements, and this happens rarely. But look at how many equations and theorems in mathematics are named after somebody. And in medicine? [[Alzheimer's disease|Alzheimer]], [[Parkinson's disease|Parkinson]]. There's nothing special about it.}}

==Characteristics==
Other than nuclear properties, no properties of oganesson or its compounds have been measured; this is due to its extremely limited and expensive production<ref name="Bloomberg">{{Cite news|url=https://www.bloomberg.com/news/features/2019-08-28/making-new-elements-doesn-t-pay-just-ask-this-berkeley-scientist|title=Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist|last=Subramanian|first=S.|website=[[Bloomberg Businessweek]]|date=28 August 2019 |access-date=2020-01-18}}</ref> and the fact that it decays very quickly. Thus only predictions are available.

===Nuclear stability and isotopes===
{{main|Isotopes of oganesson}}
[[File:Island of Stability derived from Zagrebaev.svg|thumb|upright=1.8|Oganesson (row 118) is slightly above the "[[Island of stability]]" (white ellipse) and thus its nuclei are slightly more stable than otherwise predicted.]]

The stability of nuclei quickly decreases with the increase in atomic number after [[curium]], element 96, whose most stable isotope, [[Isotopes of curium|<sup>247</sup>Cm]], has a half-life four orders of magnitude longer than that of any subsequent element. All nuclides with an atomic number above [[mendelevium|101]] undergo radioactive decay with half-lives shorter than 30 hours. No elements with atomic numbers above 82 (after [[lead]]) have stable isotopes.<ref>{{cite journal |last1=de Marcillac |first1=P. |last2=Coron |first2=N. |last3=Dambier |first3=G. |last4=Leblanc |first4=J. |last5=Moalic |first5=J.-P. |display-authors=3 |date=2003 |title=Experimental detection of α-particles from the radioactive decay of natural bismuth |journal=Nature |volume=422 |pages=876–878 |pmid=12712201 |doi=10.1038/nature01541 |issue=6934 |bibcode=2003Natur.422..876D |s2cid=4415582 }}</ref> This is because of the ever-increasing [[Coulomb repulsion]] of protons, so that the [[strong nuclear force]] cannot hold the nucleus together against [[spontaneous fission]] for long. Calculations suggest that in the absence of other stabilizing factors, elements with more than [[rutherfordium|104 protons]] should not exist.<ref name="liquiddrop">{{cite journal |last=Möller|first=P.|date=2016|title=The limits of the nuclear chart set by fission and alpha decay |journal=EPJ Web of Conferences |volume=131 |pages=03002:1–8 |url=https://inspirehep.net/record/1502715/files/epjconf-NS160-03002.pdf |doi=10.1051/epjconf/201613103002|bibcode=2016EPJWC.13103002M|doi-access=free}}</ref> However, researchers in the 1960s suggested that the closed [[nuclear shell model|nuclear shells]] around 114 protons and 184 neutrons should counteract this instability, creating an [[island of stability]] in which nuclides could have half-lives reaching thousands or millions of years. While scientists have still not reached the island, the mere existence of the [[superheavy element]]s (including oganesson) confirms that this stabilizing effect is real, and in general the known superheavy nuclides become exponentially longer-lived as they approach the predicted location of the island.<ref>{{cite book |title=Van Nostrand's scientific encyclopedia |first1=G. D. |last1=Considine |first2=Peter H. |last2=Kulik |publisher=Wiley-Interscience |date=2002 |edition=9th |isbn=978-0-471-33230-5 |oclc=223349096 }}</ref><ref name="retro">{{cite journal |last1=Oganessian |first1=Yu. Ts. |last2=Sobiczewski |first2=A. |last3=Ter-Akopian |first3=G. M. |date=9 January 2017 |title=Superheavy nuclei: from predictions to discovery |journal=Physica Scripta |volume=92 |issue=2 |pages=023003–1–21 |doi=10.1088/1402-4896/aa53c1|bibcode=2017PhyS...92b3003O |s2cid=125713877 }}</ref> Oganesson is [[radioactive]], decaying via [[alpha decay]] and spontaneous fission,<ref>{{Cite web |title=Oganesson - Element information, properties and uses {{!}} Periodic Table |url=https://www.rsc.org/periodic-table/element/118/Oganesson |access-date=2023-01-25 |website=rsc.org}}</ref><ref>{{Cite web |date=2020-12-08 |title=Oganesson - Protons - Neutrons - Electrons - Electron Configuration |url=https://material-properties.org/oganesson-protons-neutrons-electrons-electron-configuration/ |access-date=2023-01-25 |website=Material Properties |language=en-US}}</ref> with a [[half-life]] that appears to be less than a [[millisecond]]. Nonetheless, this is still longer than some predicted values.<ref name="half-lives"/><ref>{{cite journal|title=Heaviest nuclei from <sup>48</sup>Ca-induced reactions|first=Yu. T.|last=Oganessian|date=2007|journal= Journal of Physics G: Nuclear and Particle Physics|volume=34|pages=R165–R242|doi=10.1088/0954-3899/34/4/R01|bibcode = 2007JPhG...34R.165O|issue=4}}</ref>

Calculations using a quantum-tunneling model predict the existence of several heavier isotopes of oganesson with alpha-decay half-lives close to 1&nbsp;ms.<ref name="prc08ADNDT08">{{cite journal|journal=Physical Review C|volume=77|page=044603|date=2008|title=Search for long lived heaviest nuclei beyond the valley of stability|first1=Roy P.|last1=Chowdhury |first2=C. |last2=Samanta |first3=D. N. |last3=Basu|doi=10.1103/PhysRevC.77.044603|bibcode = 2008PhRvC..77d4603C|issue=4|arxiv = 0802.3837 |s2cid=119207807}}</ref><ref name="sciencedirect1">{{cite journal|journal=[[Atomic Data and Nuclear Data Tables]] |volume=94|pages=781–806|date=2008|title=Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130| author=Chowdhury, R. P.| author2=Samanta, C.| author3=Basu, D.N.| doi=10.1016/j.adt.2008.01.003| bibcode = 2008ADNDT..94..781C| issue=6| arxiv = 0802.4161 |s2cid=96718440}}</ref>

Theoretical calculations done on the synthetic pathways for, and the half-life of, other [[isotopes of oganesson|isotopes]] have shown that some could be slightly more [[stable isotope|stable]] than the synthesized isotope <sup>294</sup>Og, most likely <sup>293</sup>Og, <sup>295</sup>Og, <sup>296</sup>Og, <sup>297</sup>Og, <sup>298</sup>Og, <sup>300</sup>Og and <sup>302</sup>Og (the last reaching the ''N''&nbsp;=&nbsp;184 shell closure).<ref name="half-lives"/><ref name="odd">{{cite journal|journal=Nuclear Physics A|volume=730|date=2004|pages=355–376|title=Entrance channels and alpha decay half-lives of the heaviest elements|first1=G. |last1=Royer|first2= K. |last2=Zbiri|first3 =C. |last3=Bonilla|doi=10.1016/j.nuclphysa.2003.11.010|arxiv = nucl-th/0410048 |bibcode = 2004NuPhA.730..355R|issue=3–4}}</ref> Of these, <sup>297</sup>Og might provide the best chances for obtaining longer-lived nuclei,<ref name="half-lives">{{cite journal| journal=Phys. Rev. C| volume=73| issue=1| page=014612| date=2006| title=α decay half-lives of new superheavy elements| first1=Roy P.| last1=Chowdhury |first2=C. |last2=Samanta | first3=D. N. | last3=Basu| doi=10.1103/PhysRevC.73.014612| arxiv = nucl-th/0507054 |bibcode = 2006PhRvC..73a4612C| s2cid=118739116}}</ref><ref name="odd"/> and thus might become the focus of future work with this element. Some isotopes with many more neutrons, such as some located around <sup>313</sup>Og, could also provide longer-lived nuclei.<ref>{{cite journal|title=Half-life predictions for decay modes of superheavy nuclei|date=2004|journal=Journal of Physics G: Nuclear and Particle Physics| volume=30|pages=1487–1494| doi=10.1088/0954-3899/30/10/014| first1=S. B.|last1=Duarte| first2=O. A. P.| last2=Tavares| first3=M.| last3=Gonçalves| first4=O.| last4=Rodríguez| first5=F.| last5=Guzmán| first6=T. N.| last6=Barbosa| first7=F.| last7=García| first8=A.| last8=Dimarco| bibcode = 2004JPhG...30.1487D| issue=10| url=https://www.iaea.org/inis/collection/NCLCollectionStore/_Public/36/073/36073846.pdf|citeseerx=10.1.1.692.3012}}</ref> The isotopes from <sup>291</sup>Og to <sup>295</sup>Og might be produced as daughters of [[unbinilium|element 120]] isotopes that can be reached in the reactions <sup>249–251</sup>Cf+<sup>50</sup>Ti, <sup>245</sup>Cm+<sup>48</sup>Ca, and <sup>248</sup>Cm+<sup>48</sup>Ca.<ref name=jinr2024>{{Cite web |url=https://indico.jinr.ru/event/4343/contributions/28663/attachments/20748/36083/U%20+%20Cr%20AYSS%202024.pptx |title=Synthesis and study of the decay properties of isotopes of superheavy element Lv in Reactions <sup>238</sup>U + <sup>54</sup>Cr and <sup>242</sup>Pu + <sup>50</sup>Ti |last=Ibadullayev |first=Dastan |date=2024 |website=jinr.ru |publisher=[[Joint Institute for Nuclear Research]] |access-date=2 November 2024 |quote=}}</ref>

In a [[Quantum tunneling|quantum-tunneling model]], the alpha decay half-life of {{chem|294|Og}} was predicted to be {{val|0.66|+0.23|-0.18|u=ms}}<ref name="half-lives"/> with the experimental [[Q value (nuclear science)|Q-value]] published in 2004.<ref name="oga04">{{cite journal|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|doi=10.1103/PhysRevC.70.064609|year=2004|journal=Physical Review C|volume=70|page=064609|last1=Oganessian|first1=Yu. Ts.|last2=Utyonkov|first2=V.|last3=Lobanov|first3=Yu.|last4=Abdullin|first4=F.|last5=Polyakov|first5=A.|last6=Shirokovsky|first6=I.|last7=Tsyganov|first7=Yu.|last8=Gulbekian|first8=G.|last9=Bogomolov|first9=S.|first10=B. N. |last10=Gikal|first11=A. N. |last11=Mezentsev|first12=S. |last12=Iliev|first13=V. G. |last13=Subbotin|first14=A. M. |last14=Sukhov|first15=A. A. |last15=Voinov|first16=G. V. |last16=Buklanov|first17=K. |last17=Subotic|first18=V. I. |last18=Zagrebaev|first19=M. G. |last19=Itkis|first20=J. B. |last20=Patin|first21=K. J. |last21=Moody|first22=J. F. |last22=Wild|first23=M. A. |last23=Stoyer|first24=N. J. |last24=Stoyer|first25=D. A. |last25=Shaughnessy|first26=J. M. |last26=Kenneally|first27=P. A. |last27=Wilk|first28=R. W. |last28=Lougheed|first29=R. I. |last29=Il'kaev|first30=S. P. |last30=Vesnovskii|display-authors=10|bibcode = 2004PhRvC..70f4609O|issue=6|url=https://www1.jinr.ru/Preprints/2004/160(E7-2004-160).pdf}}</ref> Calculation with theoretical Q-values from the macroscopic-microscopic model of Muntian–Hofman–Patyk–Sobiczewski gives somewhat lower but comparable results.<ref name="npa07">{{cite journal|journal=Nucl. Phys. A|volume=789|issue=1–4|pages=142–154|date=2007|title=Predictions of alpha decay half-lives of heavy and superheavy elements|author=Samanta, C.|author2=Chowdhury, R. P.|author3=Basu, D.N.|doi=10.1016/j.nuclphysa.2007.04.001|arxiv = nucl-th/0703086 |bibcode = 2007NuPhA.789..142S|s2cid=7496348}}</ref>

===Calculated atomic and physical properties===
Oganesson is a member of [[noble gas|group 18]], the zero-[[valency (chemistry)|valence]] elements. The members of this group are usually inert to most common chemical reactions (for example, combustion) because the outer [[valence shell]] is completely filled with [[octet rule|eight electrons]]. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound.<ref>{{cite web|last=Bader|first=Richard F.W|url=https://miranda.chemistry.mcmaster.ca/esam/|title=An Introduction to the Electronic Structure of Atoms and Molecules|publisher=McMaster University|access-date=18 January 2008|archive-date=12 October 2007|archive-url=https://web.archive.org/web/20071012213137/http://miranda.chemistry.mcmaster.ca/esam/|url-status=dead}}</ref> It is thought that similarly, oganesson has a [[closed shell|closed]] outer valence shell in which its [[valence electron]]s are arranged in a 7s<sup>2</sup>7p<sup>6</sup> [[electron configuration|configuration]].<ref name="Nash2005"/>

Consequently, some expect oganesson to have similar physical and chemical properties to other members of its group, most closely resembling the noble gas above it in the periodic table, [[radon]].<ref>{{cite web|url=https://lenntech.com/Periodic-chart-elements/Uuo-en.htm|title=Ununoctium (Uuo) – Chemical properties, Health and Environmental effects|publisher=Lenntech|access-date=18 January 2008|archive-url = https://web.archive.org/web/20080116172028/https://lenntech.com/Periodic-chart-elements/Uuo-en.htm |archive-date = 16 January 2008|url-status=dead}}</ref>
Following the [[periodic trend]], oganesson would be expected to be slightly more reactive than radon. However, theoretical calculations have shown that it could be significantly more reactive.<ref name="Kaldor"/> In addition to being far more reactive than radon, oganesson may be even more reactive than the elements [[flerovium]] and [[copernicium]], which are heavier homologs of the more chemically active elements [[lead]] and [[mercury (element)|mercury]], respectively.<ref name="Nash2005"/> The reason for the possible enhancement of the chemical activity of oganesson relative to radon is an energetic destabilization and a radial expansion of the last occupied 7p-[[Electron shell#Subshells|subshell]].<ref name="Nash2005"/> More precisely, considerable [[spin–orbit interaction]]s between the 7p electrons and the inert 7s electrons effectively lead to a second valence shell closing at [[flerovium]], and a significant decrease in stabilization of the closed shell of oganesson.<ref name="Nash2005"/> It has also been calculated that oganesson, unlike the other noble gases, binds an electron with release of energy, or in other words, it exhibits positive [[electron affinity]],<ref name="Pyykko">{{cite journal|title=QED corrections to the binding energy of the eka-radon (Z=118) negative ion|first1=Igor|last1=Goidenko|first2=Leonti|last2=Labzowsky|first3=Ephraim|last3=Eliav|first4=Uzi|last4=Kaldor|first5= Pekka |last5=Pyykkö|journal=Physical Review A|volume=67|date=2003|pages=020102(R)|doi=10.1103/PhysRevA.67.020102|bibcode = 2003PhRvA..67b0102G|issue=2}}</ref><ref>{{cite journal|volume=77|issue=27|journal=Physical Review Letters|date=1996|title=Element 118: The First Rare Gas with an Electron Affinity|first1=Ephraim |last1=Eliav |first2=Uzi |last2=Kaldor|doi=10.1103/PhysRevLett.77.5350|pages=5350–5352|pmid=10062781|last3=Ishikawa|first3=Y.|last4=Pyykkö|first4=P. |bibcode=1996PhRvL..77.5350E}}</ref> due to the relativistically stabilized 8s energy level and the destabilized 7p<sub>3/2</sub> level,<ref name="Landau">{{cite journal |last1=Landau |first1=Arie |last2=Eliav |first2=Ephraim |first3=Yasuyuki |last3=Ishikawa |first4=Uzi |last4=Kador |date=25 May 2001 |title=Benchmark calculations of electron affinities of the alkali atoms sodium to eka-francium (element 119) |url=https://www.researchgate.net/publication/234859102 |journal=Journal of Chemical Physics |volume=115 |issue=6 |pages=2389–92 |doi=10.1063/1.1386413 |access-date=15 September 2015|bibcode = 2001JChPh.115.2389L }}</ref> whereas copernicium and flerovium are predicted to have no electron affinity.<ref>{{cite web |url=https://www.kernchemie.uni-mainz.de/downloads/che_7/presentations/borschevsky.pdf |title=Fully relativistic ''ab initio'' studies of superheavy elements |last1=Borschevsky |first1=Anastasia |first2=Valeria |last2=Pershina |first3=Uzi |last3=Kaldor |first4=Ephraim |last4=Eliav |website=kernchemie.uni-mainz.de |publisher=[[Johannes Gutenberg University Mainz]] |access-date=15 January 2018 |url-status=dead |archive-url=https://web.archive.org/web/20180115184921/https://www.kernchemie.uni-mainz.de/downloads/che_7/presentations/borschevsky.pdf |archive-date=15 January 2018 }}</ref><ref>{{cite journal |last1=Borschevsky |first1=Anastasia |last2=Pershina |first2=Valeria |first3=Ephraim |last3=Eliav |first4=Uzi |last4=Kaldor |date=27 August 2009 |title=Electron affinity of element 114, with comparison to Sn and Pb |journal=Chemical Physics Letters |volume=480 |issue=1 |pages=49–51 |doi=10.1016/j.cplett.2009.08.059|bibcode=2009CPL...480...49B }}</ref> Nevertheless, [[quantum electrodynamic]] corrections have been shown to be quite significant in reducing this affinity by decreasing the binding in the [[anion]] Og<sup>−</sup> by 9%, thus confirming the importance of these corrections in [[superheavy element]]s.<ref name="Pyykko"/> 2022 calculations expect the electron affinity of oganesson to be 0.080(6)&nbsp;eV.<ref name=IPEA/>

[[Monte Carlo method|Monte Carlo simulations]] of oganesson's [[molecular dynamics]] predict it has a melting point of {{val|325|15|u=K}} and a boiling point of {{val|450|10|u=K}} due to [[relativistic quantum chemistry|relativistic effects]] (if these effects are ignored, oganesson would melt at ≈{{val|220|u=K}}). Thus oganesson would probably be a solid rather than a gas under [[standard conditions]], though still with a rather low melting point.<ref name="oganesson-melting"/><ref name="smits2020"/>

Oganesson is expected to have an extremely broad [[polarizability]], almost double that of radon.<ref name="Nash2005"/> Because of its tremendous polarizability, oganesson is expected to have an anomalously low first [[ionization energy]] of about 860&nbsp;kJ/mol, similar to that of [[cadmium]] and less than those of [[iridium]], [[platinum]], and [[gold]]. This is significantly smaller than the values predicted for [[darmstadtium]], [[roentgenium]], and copernicium, although it is greater than that predicted for flerovium.<ref>{{cite journal|journal=Journal of Physical Chemistry A| volume=1999| issue=3| pages=402–410|title=Spin-Orbit Effects, VSEPR Theory, and the Electronic Structures of Heavy and Superheavy Group IVA Hydrides and Group VIIIA Tetrafluorides. A Partial Role Reversal for Elements 114 and 118|first1=Clinton S.| last1=Nash| doi=10.1021/jp982735k| pmid=27676357| date=1999| last2=Bursten| first2=Bruce E.|bibcode=1999JPCA..103..402N}}</ref> Its second ionization energy should be around 1560&nbsp;kJ/mol.<ref name=IPEA/> Even the shell structure in the nucleus and electron cloud of oganesson is strongly impacted by relativistic effects: the valence and core electron subshells in oganesson are expected to be "smeared out" in a homogeneous [[Fermi gas]] of electrons, unlike those of the "less relativistic" radon and xenon (although there is some incipient delocalisation in radon), due to the very strong spin–orbit splitting of the 7p orbital in oganesson.<ref name="oganesson-elf"/> A similar effect for nucleons, particularly neutrons, is incipient in the closed-neutron-shell nucleus <sup>302</sup>Og and is strongly in force at the hypothetical superheavy closed-shell nucleus <sup>472</sup>164<!--YES IT REALLY IS STANDARD TO USE THE ATOMIC NUMBER HERE, THE CITED PAPER DOES IT TOO. IN PRACTICE SYSTEMATIC SYMBOLS ARE NOT USED THAT MUCH IN THE LITERATURE!-->, with 164 protons and 308 neutrons.<ref name="oganesson-elf">{{cite journal| journal=Phys. Rev. Lett.| volume=120| issue=5| page=053001| date=2018| title=Electron and Nucleon Localization Functions of Oganesson: Approaching the Thomas-Fermi Limit| first1=Paul |last1=Jerabek |first2=Bastian |last2=Schuetrumpf |first3=Peter |last3=Schwerdtfeger |first4=Witold |last4=Nazarewicz| doi=10.1103/PhysRevLett.120.053001| pmid=29481184| arxiv = 1707.08710 | bibcode = 2018PhRvL.120e3001J| s2cid=3575243}}</ref> Studies have also predicted that due to increasing electrostatic forces, oganesson may have a semibubble structure in proton density, having few protons at the center of its nucleus.<ref>{{Cite journal |last1=Schuetrumpf |first1=B. |last2=Nazarewicz |first2=W. |last3=Reinhard |first3=P.-G. |date=2017-08-11 |title=Central depression in nucleonic densities: Trend analysis in the nuclear density functional theory approach |url=https://link.aps.org/doi/10.1103/PhysRevC.96.024306 |journal=Physical Review C |volume=96 |issue=2 |pages=024306 |doi=10.1103/PhysRevC.96.024306|arxiv=1706.05759 |bibcode=2017PhRvC..96b4306S |s2cid=119510865 }}</ref><ref>{{Cite web |last=Garisto |first=Dan |date=12 February 2018 |title=5 ways the heaviest element on the periodic table is really bizarre |url=https://www.sciencenews.org/article/5-ways-heaviest-element-periodic-table-really-bizarre |access-date=2023-02-12 |website=ScienceNews |language=en-US}}</ref> Moreover, spin–orbit effects may cause bulk oganesson to be a [[semiconductor]], with a [[band gap]] of {{val|1.5|0.6}}&nbsp;eV predicted. All the lighter noble gases are [[Insulator (electricity)|insulators]] instead: for example, the band gap of bulk [[radon]] is expected to be {{val|7.1|0.5}}&nbsp;eV.<ref name="semiconductor">{{cite journal |last1=Mewes |first1=Jan-Michael |last2=Smits |first2=Odile Rosette |first3=Paul |last3=Jerabek |first4=Peter |last4=Schwerdtfeger |date=25 July 2019 |title=Oganesson is a Semiconductor: On the Relativistic Band-Gap Narrowing in the Heaviest Noble-Gas Solids |journal=Angewandte Chemie |volume=58 |issue=40 |pages=14260–14264 |doi=10.1002/anie.201908327 |pmid=31343819 |pmc=6790653 }}</ref>

===Predicted compounds===
[[File:Square-planar-3D-balls.png|right|upright=0.6|alt=Skeletal model of a planar molecule with a central atom symmetrically bonded to four peripheral (fluorine) atoms.|thumb|[[xenon tetrafluoride|{{chem|XeF|4}}]] has a square planar molecular geometry.]]
[[File:Tetrahedral-3D-balls.png|right|upright=0.6|thumb|alt=Skeletal model of a terahedral molecule with a central atom (oganesson) symmetrically bonded to four peripheral (fluorine) atoms.|{{chem|OgF|4}} is predicted to have a tetrahedral molecular geometry.]]

The only confirmed isotope of oganesson, <sup>294</sup>Og, has much too short a half-life to be chemically investigated experimentally. Therefore, no compounds of oganesson have been synthesized yet.<ref name="Moody">{{cite book |chapter=Synthesis of Superheavy Elements |last=Moody |first=Ken |editor1-first=Matthias |editor1-last=Schädel |editor2-first=Dawn |editor2-last=Shaughnessy |title=The Chemistry of Superheavy Elements |publisher=Springer Science & Business Media |edition=2nd |pages=24–8 |isbn=9783642374661|date=30 November 2013 }}</ref> Nevertheless, calculations on [[theoretical chemistry|theoretical compounds]] have been performed since 1964.<ref name="60s"/> It is expected that if the [[ionization energy]] of the element is high enough, it will be difficult to [[oxidize]] and therefore, the most common [[oxidation state]] would be 0 (as for the noble gases);<ref name="compounds">{{cite web|publisher=WebElements Periodic Table|url=https://www.webelements.com/oganesson/compounds.html|title=Oganesson: Compounds Information|access-date=19 August 2019}}</ref> nevertheless, this appears not to be the case.{{Fricke1975|name}}

Calculations on the [[diatomic molecule]] {{chem|Og|2}} showed a [[chemical bond|bonding]] interaction roughly equivalent to that calculated for {{chem|Hg|2}}, and a [[dissociation energy]] of 6&nbsp;kJ/mol, roughly 4 times of that of {{chem|Rn|2}}.<ref name="Nash2005"/> Most strikingly, it was calculated to have a [[bond length]] shorter than in {{chem|Rn|2}} by 0.16 Å, which would be indicative of a significant bonding interaction.<ref name="Nash2005"/> On the other hand, the compound OgH<sup>+</sup> exhibits a dissociation energy (in other words [[proton affinity]] of oganesson) that is smaller than that of RnH<sup>+</sup>.<ref name="Nash2005"/>

The bonding between oganesson and [[hydrogen]] in OgH is predicted to be very weak and can be regarded as a pure [[van der Waals interaction]] rather than a true [[chemical bond]].<ref name="hydride"/> On the other hand, with highly electronegative elements, oganesson seems to form more stable compounds than for example [[copernicium]] or [[flerovium]].<ref name="hydride"/> The stable oxidation states +2 and +4 have been predicted to exist in the [[fluoride]]s {{chem|OgF|2}} and {{chem|OgF|4}}.<ref name="fluoride">{{cite journal|journal=Journal of Physical Chemistry A|volume=103|issue=8|pages=1104–1108|date=1999|title=Structures of RgFn (Rg = Xe, Rn, and Element 118. n = 2, 4.) Calculated by Two-component Spin-Orbit Methods. A Spin-Orbit Induced Isomer of (118)F<sub>4</sub>|first1=Young-Kyu|last1=Han|first2=Yoon Sup|last2=Lee|doi=10.1021/jp983665k|bibcode=1999JPCA..103.1104H}}</ref> The +6 state would be less stable due to the strong binding of the 7p<sub>1/2</sub> subshell.{{Fricke1975|name}} This is a result of the same spin–orbit interactions that make oganesson unusually reactive. For example, it was shown that the reaction of oganesson with {{chem|F|2}} to form the compound {{chem|OgF|2}} would release an energy of 106&nbsp;kcal/mol of which about 46&nbsp;kcal/mol come from these interactions.<ref name="hydride"/> For comparison, the spin–orbit interaction for the similar molecule {{chem|RnF|2}} is about 10&nbsp;kcal/mol out of a formation energy of 49&nbsp;kcal/mol.<ref name="hydride"/> The same interaction stabilizes the [[tetrahedral molecular geometry|tetrahedral T<sub>d</sub> configuration]] for {{chem|OgF|4}}, as distinct from the [[square planar|square planar D<sub>4h</sub> one]] of [[xenon tetrafluoride|{{chem|XeF|4}}]], which {{chem|RnF|4}} is also expected to have;<ref name="fluoride"/> this is because OgF<sub>4</sub> is expected to have two [[inert pair|inert electron pairs]] (7s and 7p<sub>1/2</sub>). As such, OgF<sub>6</sub> is expected to be unbound, continuing an expected trend in the destabilisation of the +6 oxidation state (RnF<sub>6</sub> is likewise expected to be much less stable than [[xenon hexafluoride|XeF<sub>6</sub>]]).<ref>{{cite journal |last=Liebman |first=Joel F. |date=1975 |title=Conceptual Problems in Noble Gas and Fluorine Chemistry, II: The Nonexistence of Radon Tetrafluoride |journal=Inorg. Nucl. Chem. Lett. |volume=11 |issue=10 |pages=683–685 |doi=10.1016/0020-1650(75)80185-1}}</ref><ref>{{cite journal |last=Seppelt |first=Konrad |date=2015 |title=Molecular Hexafluorides |journal=Chemical Reviews |volume=115 |issue=2 |pages=1296–1306 |doi=10.1021/cr5001783|pmid=25418862 }}</ref> The Og–F bond will most probably be [[ionic bond|ionic]] rather than [[covalent bond|covalent]], rendering the oganesson fluorides non-volatile.<ref name="Kaldor"/><ref>{{cite journal|journal=Journal of the Chemical Society, Chemical Communications|date=1975|pages=760–761|doi=10.1039/C3975000760b|title=Fluorides of radon and element 118|first =Kenneth S.|last = Pitzer|issue=18|url=https://escholarship.org/content/qt8xz4g1ff/qt8xz4g1ff.pdf?t=p2at3t}}</ref> OgF<sub>2</sub> is predicted to be partially [[ionic bonding|ionic]] due to oganesson's high [[electropositivity]].<ref name="EB">{{cite encyclopedia |title=transuranium element (chemical element) |encyclopedia=[[Encyclopædia Britannica|Britannica Online]] |url=https://www.britannica.com/EBchecked/topic/603220/transuranium-element |access-date=16 March 2010 |date=c. 2006 |author=Seaborg, Glenn Theodore}}</ref> Oganesson is predicted to be sufficiently electropositive<ref name="EB"/> to form an Og–Cl bond with [[chlorine]].<ref name="Kaldor"/>

A compound of oganesson and [[tennessine]], OgTs<sub>4</sub>, has been predicted to be potentially stable chemically.<ref name="Loveland">{{cite journal |last=Loveland |first=Walter |title=Relativistic effects for the superheavy reaction Og + 2Ts2 → OgTs4 (Td or D4h): dramatic relativistic effects for atomization energy of superheavy Oganesson tetratennesside OgTs4 and prediction of the existence of tetrahedral OgTs4 |journal=Theoretical Chemistry Accounts |date=1 June 2021 |volume=140 |issue=75 |doi=10.1007/s00214-021-02777-2 |osti=1991559 |s2cid=235259897 |url=https://link.springer.com/article/10.1007/s00214-021-02777-2 |access-date=30 June 2021}}</ref>

==See also==
* [[Island of stability]]
* [[Superheavy element]]
* [[Transuranium element]]

==Notes==
{{notelist}}

==References==
{{Reflist|colwidth=30em|refs=

}}

==Bibliography==
* {{cite journal |ref={{harvid|Audi et al.|2017}} |title=The NUBASE2016 evaluation of nuclear properties |doi=10.1088/1674-1137/41/3/030001 |last1=Audi |first1=G. |last2=Kondev |first2=F. G. |last3=Wang |first3=M. |last4=Huang |first4=W. J. |last5=Naimi |first5=S. |display-authors=3 |journal=Chinese Physics C |volume=41 |issue=3 <!--Citation bot deny-->|pages=030001 |year=2017 
|bibcode=2017ChPhC..41c0001A }}<!--for consistency and specific pages, do not replace with {{NUBASE2016}}-->
* {{cite book|last=Beiser|first=A.|title=Concepts of modern physics|date=2003|publisher=McGraw-Hill|isbn=978-0-07-244848-1|edition=6th|oclc=48965418}}
* {{cite book |last1=Hoffman |first1=D. C. |author-link1=Darleane C. Hoffman |last2=Ghiorso |first2=A. |author-link2=Albert Ghiorso |last3=Seaborg |first3=G. T. |title=The Transuranium People: The Inside Story |year=2000 |publisher=[[World Scientific]] |isbn=978-1-78-326244-1 }}
* {{cite book |last=Kragh |first=H. |author-link=Helge Kragh |date=2018 |title=From Transuranic to Superheavy Elements: A Story of Dispute and Creation |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-3-319-75813-8 }}
* {{cite journal|last1=Zagrebaev|first1=V.|last2=Karpov|first2=A.|last3=Greiner|first3=W.|date=2013|title=Future of superheavy element research: Which nuclei could be synthesized within the next few years?|journal=[[Journal of Physics: Conference Series]]|volume=420|issue=1|pages=012001|doi=10.1088/1742-6596/420/1/012001|arxiv=1207.5700|bibcode=2013JPhCS.420a2001Z|s2cid=55434734|issn=1742-6588}}

==Further reading==
* {{cite book |first=Eric |last=Scerri |title=The Periodic Table, Its Story and Its Significance |url=https://archive.org/details/periodictableits0000scer |url-access=registration |publisher=Oxford University Press |location=New York |year=2007 |isbn=978-0-19-530573-9}}

==External links==
* [https://www.sciencenews.org/article/5-ways-heaviest-element-periodic-table-really-bizarre 5 ways the heaviest element on the periodic table is really bizarre], [[Science News|ScienceNews.org]]
* [https://web.archive.org/web/20061129112314/https://flerovlab.jinr.ru/flnr/elm118.html Element 118: Experiments on discovery], archive of discoverers' official web page
* [https://www.nytimes.com/2006/10/17/science/17heavy.html Element 118, Heaviest Ever, Reported for 1,000th of a Second], ''[[The New York Times]]''.
* [https://education.jlab.org/itselemental/ele118.html It's Elemental: Oganesson]
* [https://www.periodicvideos.com/videos/118.htm Oganesson] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [https://iupac.org/publications/pac/75/10/1601/ On the Claims for Discovery of Elements 110, 111, 112, 114, 116, and 118 (IUPAC Technical Report)]
* [https://www.webelements.com/oganesson/ WebElements: Oganesson]

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