Oganesson is asynthetic chemical element; it hassymbolOg andatomic number 118. It was first synthesized in 2002 at theJoint Institute for Nuclear Research (JINR) inDubna, nearMoscow, Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by theJoint Working Party of the international scientific bodiesIUPAC andIUPAP. It was formally named on 28 November 2016.[15][16] The name honors the nuclear physicistYuri Oganessian, who played a leading role in the discovery of the heaviest elements in the periodic table.
Oganesson has the highest atomic number and highestatomic mass of allknown elements. On the periodic table of the elements it is ap-block element, a member ofgroup 18, and the last member ofperiod 7. Its only known isotope,oganesson-294, is highlyradioactive, with a half-life of 0.7ms and, as of 2025,[update] only five atoms have been successfully produced.[17] This has so far prevented any experimental studies of its chemistry. Because ofrelativistic effects, theoretical studies predict that it would be asolid atroom temperature, and significantly reactive,[3][17] unlike the other members of group 18 (thenoble gases).
A graphic depiction of anuclear fusion reaction. Two nuclei fuse into one, emitting aneutron. Reactions that created new elements to this moment were similar, with the only possible difference that several singular neutrons sometimes were released, or none at all.
A superheavy[a]atomic nucleus is created in a nuclear reaction that combines two other nuclei of unequal size[b] into one; roughly, the more unequal the two nuclei in terms ofmass, the greater the possibility that the two react.[23] The material made of the heavier nuclei is made into a target, which is then bombarded by thebeam of lighter nuclei. Two nuclei can onlyfuse into one if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due toelectrostatic repulsion. Thestrong interaction can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatlyaccelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus.[24] The energy applied to the beam nuclei to accelerate them can cause them to reach speeds as high as one-tenth of thespeed of light. However, if too much energy is applied, the beam nucleus can fall apart.[24]
Coming close enough alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for about 10−20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus.[24][25] This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.[24] Each pair of a target and a beam is characterized by itscross section—the probability that fusion will occur if two nuclei approach one another expressed in terms of the transverse area that the incident particle must hit in order for the fusion to occur.[c] This fusion may occur as a result of the quantum effect in which nuclei cantunnel through electrostatic repulsion. If the two nuclei can stay close past that phase, multiple nuclear interactions result in redistribution of energy and an energy equilibrium.[24]
The resulting merger is anexcited state[28]—termed acompound nucleus—and thus it is very unstable.[24] To reach a more stable state, the temporary merger mayfission without formation of a more stable nucleus.[29] Alternatively, the compound nucleus may eject a fewneutrons, which would carry away the excitation energy; if the latter is not sufficient for a neutron expulsion, the merger would produce agamma ray. This happens in about 10−16 seconds after the initial nuclear collision and results in creation of a more stable nucleus.[29] The definition by theIUPAC/IUPAP Joint Working Party (JWP) states that achemical element can only be recognized as discovered if a nucleus of it has notdecayed within 10−14 seconds. This value was chosen as an estimate of how long it takes a nucleus to acquireelectrons and thus display its chemical properties.[30][d]
The beam passes through the target and reaches the next chamber, the separator; if a new nucleus is produced, it is carried with this beam.[32] In the separator, the newly produced nucleus is separated from other nuclides (that of the original beam and any other reaction products)[e] and transferred to asurface-barrier detector, which stops the nucleus. The exact location of the upcoming impact on the detector is marked; also marked are its energy and the time of the arrival.[32] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[35] The nucleus is recorded again once its decay is registered, and the location, theenergy, and the time of the decay are measured.[32]
Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, its influence on the outermostnucleons (protons and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, and its range is not limited.[36] Totalbinding energy provided by the strong interaction increases linearly with the number of nucleons, whereas electrostatic repulsion increases with the square of the atomic number, i.e. the latter grows faster and becomes increasingly important for heavy and superheavy nuclei.[37][38] Superheavy nuclei are thus theoretically predicted[39] and have so far been observed[40] to predominantly decay via decay modes that are caused by such repulsion:alpha decay andspontaneous fission.[f] Almost all alpha emitters have over 210 nucleons,[42] and the lightest nuclide primarily undergoing spontaneous fission has 238.[43] In both decay modes, nuclei are inhibited from decaying by correspondingenergy barriers for each mode, but they can be tunneled through.[37][38]
Scheme of an apparatus for creation of superheavy elements, based on the Dubna Gas-Filled Recoil Separator set up in theFlerov Laboratory of Nuclear Reactions in JINR. The trajectory within the detector and the beam focusing apparatus changes because of adipole magnet in the former andquadrupole magnets in the latter.[44]
Alpha particles are commonly produced in radioactive decays because the mass of an alpha particle per nucleon is small enough to leave some energy for the alpha particle to be used as kinetic energy to leave the nucleus.[45] Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning.[38] As the atomic number increases, spontaneous fission rapidly becomes more important: spontaneous fission partial half-lives decrease by 23 orders of magnitude fromuranium (element 92) tonobelium (element 102),[46] and by 30 orders of magnitude fromthorium (element 90) tofermium (element 100).[47] The earlierliquid drop model thus suggested that spontaneous fission would occur nearly instantly due to disappearance of thefission barrier for nuclei with about 280 nucleons.[38][48] The laternuclear shell model suggested that nuclei with about 300 nucleons would form anisland of stability in which nuclei will be more resistant to spontaneous fission and will primarily undergo alpha decay with longer half-lives.[38][48] Subsequent discoveries suggested that the predicted island might be further than originally anticipated; they also showed that nuclei intermediate between the long-lived actinides and the predicted island are deformed, and gain additional stability from shell effects.[49] Experiments on lighter superheavy nuclei,[50] as well as those closer to the expected island,[46] have shown greater than previously anticipated stability against spontaneous fission, showing the importance of shell effects on nuclei.[g]
Alpha decays are registered by the emitted alpha particles, and the decay products are easy to determine before the actual decay; if such a decay or a series of consecutive decays produces a known nucleus, the original product of a reaction can be easily determined.[h] (That all decays within a decay chain were indeed related to each other is established by the location of these decays, which must be in the same place.)[32] The known nucleus can be recognized by the specific characteristics of decay it undergoes such as decay energy (or more specifically, thekinetic energy of the emitted particle).[i] Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters.[j]
The information available to physicists aiming to synthesize a superheavy element is thus the information collected at the detectors: location, energy, and time of arrival of a particle to the detector, and those of its decay. The physicists analyze this data and seek to conclude that it was indeed caused by a new element and could not have been caused by a different nuclide than the one claimed. Often, provided data is insufficient for a conclusion that a new element was definitely created and there is no other explanation for the observed effects; errors in interpreting data have been made.[k]
The possibility of a seventhnoble gas, afterhelium,neon,argon,krypton,xenon, andradon, was considered almost as soon as the noble gas group was discovered. Danish chemistHans 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 thehalogen andalkali metal groups: he expected that the seventh of this series would end a 32-element period which containedthorium anduranium and have an atomic weight of 292, close to the 294 now known for the first and only confirmedisotope of oganesson.[61] Danish physicistNiels 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.[62] Following this, German chemistAristid von Grosse wrote an article in 1965 predicting the likely properties of element 118.[11] 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 heaviercongener of radon.[63] In a 1975 article, American chemistKenneth Pitzer suggested that element 118 should be agas orvolatileliquid due torelativistic effects.[64]
In late 1998, Polish physicistRobert Smolańczuk published calculations on the fusion of atomic nuclei towards the synthesis ofsuperheavy atoms, including oganesson.[65] His calculations suggested that it might be possible to make element 118 by fusinglead withkrypton under carefully controlled conditions, and that the fusion probability (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 orbismuth targets would go down exponentially as the atomic number of the resulting elements increased.[65]
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.[68] 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 authorVictor Ninov.[69][70] 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.[71]
The first genuine decay of atoms of oganesson was observed in 2002 at theJoint Institute for Nuclear Research (JINR) inDubna, Russia, by a joint team of Russian and American scientists. Headed byYuri Oganessian, a Russian nuclear physicist of Armenian ethnicity, the team included American scientists from theLawrence Livermore National Laboratory in California.[72] The discovery was not announced immediately, because the decay energy of294Og matched that of212mPo, 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.[73] The 2005 experiment used a different beam energy (251 MeV instead of 245 MeV) and target thickness (0.34 mg/cm2 instead of 0.23 mg/cm2).[13] On 9 October 2006, the researchers announced[13] that they had indirectly detected a total of three (possibly four) nuclei of oganesson-294 (one or two in 2002[74] and two more in 2005) produced via collisions ofcalifornium-249 atoms andcalcium-48 ions.[75][76][77][78][79]
In 2011,IUPAC evaluated the 2006 results of the Dubna–Livermore collaboration and concluded: "The three events reported for theZ = 118 isotope have very good internalredundancy but with no anchor to known nuclei do not satisfy the criteria for discovery".[80]
Because of the very smallfusion reaction probability (the fusioncross section is~0.3–0.6pb or(3–6)×10−41 m2) the experiment took four months and involved a beam dose of2.5×1019calcium ions that had to be shot at thecalifornium target to produce the first recorded event believed to be the synthesis of oganesson.[81] Nevertheless, researchers were highly confident that the results were not afalse positive, since the chance that the detections were random events was estimated to be less than one part in100000.[82]
In the experiments, the alpha-decay of three atoms of oganesson was observed. A fourth decay by directspontaneous fission was also proposed. Ahalf-life of 0.89 ms was calculated:294 Og decays into290 Lv byalpha decay. Since there were only three nuclei, the half-life derived from observed lifetimes has a large uncertainty:0.89+1.07 −0.31 ms.[13]
The identification of the294 Og nuclei was verified by separately creating the putativedaughter nucleus290 Lv directly by means of a bombardment of245 Cm with48 Ca ions,
and checking that the290 Lv decay matched thedecay chain of the294 Og nuclei.[13] The daughter nucleus290 Lv is very unstable, decaying with a lifetime of 14 milliseconds into286 Fl, which may experience either spontaneous fission or alpha decay into282 Cn, which will undergo spontaneous fission.[13]
In December 2015, theJoint Working Party of international scientific bodiesInternational Union of Pure and Applied Chemistry (IUPAC) andInternational Union of Pure and Applied Physics (IUPAP) recognized the element's discovery and assigned the priority of the discovery to the Dubna–Livermore collaboration.[83] This was on account of two 2009 and 2010 confirmations of the properties of the granddaughter of294Og,286Fl, at theLawrence Berkeley National Laboratory, as well as the observation of another consistent decay chain of294Og by the Dubna group in 2012. The goal of that experiment had been the synthesis of294Ts via the reaction249Bk(48Ca,3n), but the short half-life of249Bk resulted in a significant quantity of the target having decayed to249Cf, resulting in the synthesis of oganesson instead oftennessine.[84]
From 1 October 2015 to 6 April 2016, the Dubna team performed a similar experiment with48Ca projectiles aimed at a mixed-isotope californium target containing249Cf,250Cf, and251Cf, with the aim of producing the heavier oganesson isotopes295Og and296Og. Two beam energies at 252 MeV and 258 MeV were used. Only one atom was seen at the lower beam energy, whose decay chain fitted the previously known one of294Og (terminating with spontaneous fission of286Fl), 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.[85] The production of293Og and its daughter289Lv, as well as the even heavier isotope297Og, is also possible using this reaction. The isotopes295Og and296Og may also be produced in the fusion of248Cm with50Ti projectiles.[85][86][87] A search beginning in summer 2016 at RIKEN for295Og 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.[88][89]
Element 118 was named afterYuri Oganessian, a pioneer in the discovery ofsynthetic elements, with the nameoganesson (Og). Oganessian and the decay chain of oganesson-294 were pictured on a stamp of Armenia issued on 28 December 2017.
UsingMendeleev's nomenclature for unnamed and undiscovered elements, oganesson is sometimes known aseka-radon (until the 1960s aseka-emanation, emanation being the old name forradon).[11] In 1979, IUPAC assigned thesystematicplaceholder nameununoctium to the undiscovered element, with the corresponding symbol ofUuo,[90] and recommended that it be used until after confirmed discovery of the element.[91] 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 ofE118,(118), or simply118.[4]
Before the retraction in 2001, the researchers from Berkeley had intended to name the elementghiorsium (Gh), afterAlbert Ghiorso (a leading member of the research team).[92]
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.[93] In 2007, the head of the Russian institute stated the team were considering two names for the new element:flyorium, in honor ofGeorgy Flyorov, the founder of the research laboratory in Dubna; andmoskovium, in recognition of theMoscow Oblast where Dubna is located.[94] 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 theFlyorov Laboratory of Nuclear Reactions at JINR was the only facility in the world which could achieve this result.[95] These names were later suggested forelement 114 (flerovium) andelement 116 (moscovium).[96] Flerovium became the name of element 114; the final name proposed for element 116 was insteadlivermorium,[97] withmoscovium later being proposed and accepted forelement 115 instead.[98]
Traditionally, the names of allnoble gases end in "-on", with the exception ofhelium, which was not known to be a noble gas when discovered. The IUPAC guidelines valid at the moment of the discovery approval however requiredall new elements be named with the ending "-ium", even if they turned out to behalogens (traditionally ending in "-ine") or noble gases (traditionally ending in "-on").[99] While the provisional name ununoctium followed this convention, a new IUPAC recommendation published in 2016 recommended using the "-on" ending for newgroup 18 elements, regardless of whether they turn out to have the chemical properties of a noble gas.[100]
The scientists involved in the discovery of element 118, as well as those of117 and115, 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 elements107 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."[101]
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.[102][l]In June 2016, IUPAC announced that the discoverers planned to give the element the nameoganesson (symbol:Og). The name became official on 28 November 2016.[98] In 2017, Oganessian commented on the naming:[103]
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.[103]
— Yuri Oganessian
The naming ceremony for moscovium, tennessine, and oganesson was held on 2 March 2017 at theRussian Academy of Sciences in Moscow.[104]
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,Parkinson. There's nothing special about it.
Other than nuclear properties, no properties of oganesson or its compounds have been measured; this is due to its extremely limited and expensive production[105] and the fact that it decays very quickly. Thus only predictions are available.
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 aftercurium, element 96, whose most stable isotope,247Cm, has a half-life four orders of magnitude longer than that of any subsequent element. All nuclides with an atomic number above101 undergo radioactive decay with half-lives shorter than 30 hours. No elements with atomic numbers above 82 (afterlead) have stable isotopes.[106] This is because of the ever-increasingCoulomb repulsion of protons, so that thestrong nuclear force cannot hold the nucleus together againstspontaneous fission for long. Calculations suggest that in the absence of other stabilizing factors, elements with more than104 protons should not exist.[107] However, researchers in the 1960s suggested that the closednuclear shells around 114 protons and 184 neutrons should counteract this instability, creating anisland 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 thesuperheavy elements (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.[108][109] Oganesson isradioactive, decaying viaalpha decay and spontaneous fission,[110][111] with ahalf-life that appears to be less than amillisecond. Nonetheless, this is still longer than some predicted values.[112][113]
Calculations using a quantum-tunneling model predict the existence of several heavier isotopes of oganesson with alpha-decay half-lives close to 1 ms.[114][115]
Theoretical calculations done on the synthetic pathways for, and the half-life of, otherisotopes have shown that some could be slightly morestable than the synthesized isotope294Og, most likely293Og,295Og,296Og,297Og,298Og,300Og and302Og (the last reaching theN = 184 shell closure).[112][116] Of these,297Og might provide the best chances for obtaining longer-lived nuclei,[112][116] and thus might become the focus of future work with this element. Some isotopes with many more neutrons, such as some located around313Og, could also provide longer-lived nuclei.[117] The isotopes from291Og to295Og might be produced as daughters ofelement 120 isotopes that can be reached in the reactions249–251Cf+50Ti,245Cm+48Ca, and248Cm+48Ca.[118]
In aquantum-tunneling model, the alpha decay half-life of294 Og was predicted to be0.66+0.23 −0.18 ms[112] with the experimentalQ-value published in 2004.[119] Calculation with theoretical Q-values from the macroscopic-microscopic model of Muntian–Hofman–Patyk–Sobiczewski gives somewhat lower but comparable results.[120]
Oganesson is a member ofgroup 18, the zero-valence elements. The members of this group are usually inert to most common chemical reactions (for example, combustion) because the outervalence shell is completely filled witheight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound.[121] It is thought that similarly, oganesson has aclosed outer valence shell in which itsvalence electrons are arranged in a 7s27p6configuration.[3]
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.[122]Following theperiodic trend, oganesson would be expected to be slightly more reactive than radon. However, theoretical calculations have shown that it could be significantly more reactive.[7] In addition to being far more reactive than radon, oganesson may be even more reactive than the elementsflerovium andcopernicium, which are heavier homologs of the more chemically active elementslead andmercury, respectively.[3] 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-subshell.[3] More precisely, considerablespin–orbit interactions between the 7p electrons and the inert 7s electrons effectively lead to a second valence shell closing atflerovium, and a significant decrease in stabilization of the closed shell of oganesson.[3] 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 positiveelectron affinity,[123][124] due to the relativistically stabilized 8s energy level and the destabilized 7p3/2 level,[125] whereas copernicium and flerovium are predicted to have no electron affinity.[126][127] Nevertheless,quantum electrodynamic corrections have been shown to be quite significant in reducing this affinity by decreasing the binding in theanion Og− by 9%, thus confirming the importance of these corrections insuperheavy elements.[123] 2022 calculations expect the electron affinity of oganesson to be 0.080(6) eV.[8]
Monte Carlo simulations of oganesson'smolecular dynamics predict it has a melting point of325±15 K and a boiling point of450±10 K due torelativistic effects (if these effects are ignored, oganesson would melt at ≈220 K). Thus oganesson would probably be a solid rather than a gas understandard conditions, though still with a rather low melting point.[5][17]
Oganesson is expected to have an extremely broadpolarizability, almost double that of radon.[3] Because of its tremendous polarizability, oganesson is expected to have an anomalously low firstionization energy of about 860 kJ/mol, similar to that ofcadmium and less than those ofiridium,platinum, andgold. This is significantly smaller than the values predicted fordarmstadtium,roentgenium, and copernicium, although it is greater than that predicted for flerovium.[128] Its second ionization energy should be around 1560 kJ/mol.[8] 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 homogeneousFermi 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.[129] A similar effect for nucleons, particularly neutrons, is incipient in the closed-neutron-shell nucleus302Og and is strongly in force at the hypothetical superheavy closed-shell nucleus472164, with 164 protons and 308 neutrons.[129] 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.[130][131] Moreover, spin–orbit effects may cause bulk oganesson to be asemiconductor, with aband gap of1.5±0.6 eV predicted. All the lighter noble gases areinsulators instead: for example, the band gap of bulkradon is expected to be7.1±0.5 eV.[132]
XeF 4 has a square planar molecular geometry.OgF 4 is predicted to have a tetrahedral molecular geometry.
The only confirmed isotope of oganesson,294Og, has much too short a half-life to be chemically investigated experimentally. Therefore, no compounds of oganesson have been synthesized yet.[73] Nevertheless, calculations ontheoretical compounds have been performed since 1964.[11] It is expected that if theionization energy of the element is high enough, it will be difficult tooxidize and therefore, the most commonoxidation state would be 0 (as for the noble gases);[133] nevertheless, this appears not to be the case.[63]
Calculations on thediatomic moleculeOg 2 showed abonding interaction roughly equivalent to that calculated forHg 2, and adissociation energy of 6 kJ/mol, roughly 4 times of that ofRn 2.[3] Most strikingly, it was calculated to have abond length shorter than inRn 2 by 0.16 Å, which would be indicative of a significant bonding interaction.[3] On the other hand, the compound OgH+ exhibits a dissociation energy (in other wordsproton affinity of oganesson) that is smaller than that of RnH+.[3]
The bonding between oganesson andhydrogen in OgH is predicted to be very weak and can be regarded as a purevan der Waals interaction rather than a truechemical bond.[6] On the other hand, with highly electronegative elements, oganesson seems to form more stable compounds than for examplecopernicium orflerovium.[6] The stable oxidation states +2 and +4 have been predicted to exist in thefluoridesOgF 2 andOgF 4.[134] The +6 state would be less stable due to the strong binding of the 7p1/2 subshell.[63] 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 withF 2 to form the compoundOgF 2 would release an energy of 106 kcal/mol of which about 46 kcal/mol come from these interactions.[6] For comparison, the spin–orbit interaction for the similar moleculeRnF 2 is about 10 kcal/mol out of a formation energy of 49 kcal/mol.[6] The same interaction stabilizes thetetrahedral Td configuration forOgF 4, as distinct from thesquare planar D4h one ofXeF 4, whichRnF 4 is also expected to have;[134] this is because OgF4 is expected to have twoinert electron pairs (7s and 7p1/2). As such, OgF6 is expected to be unbound, continuing an expected trend in the destabilisation of the +6 oxidation state (RnF6 is likewise expected to be much less stable thanXeF6).[135][136] The Og–F bond will most probably beionic rather thancovalent, rendering the oganesson fluorides non-volatile.[7][137] OgF2 is predicted to be partiallyionic due to oganesson's highelectropositivity.[138] Oganesson is predicted to be sufficiently electropositive[138] to form an Og–Cl bond withchlorine.[7]
A compound of oganesson andtennessine, OgTs4, has been predicted to be potentially stable chemically.[139]
^Innuclear physics, an element is calledheavy if its atomic number is high;lead (element 82) is one example of such a heavy element. The term "superheavy elements" typically refers to elements with atomic number greater than103 (although there are other definitions, such as atomic number greater than100[18] or112;[19] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypotheticalsuperactinide series).[20] Terms "heavy isotopes" (of a given element) and "heavy nuclei" mean what could be understood in the common language—isotopes of high mass (for the given element) and nuclei of high mass, respectively.
^In 2009, a team at the JINR led by Oganessian published results of their attempt to create hassium in a symmetric136Xe + 136Xe reaction. They failed to observe a single atom in such a reaction, putting the upper limit on the cross section, the measure of probability of a nuclear reaction, as 2.5 pb.[21] In comparison, the reaction that resulted in hassium discovery,208Pb +58Fe, had a cross section of ~20 pb (more specifically, 19+19 -11 pb), as estimated by the discoverers.[22]
^The amount of energy applied to the beam particle to accelerate it can also influence the value of cross section. For example, in the28 14Si +1 0n →28 13Al +1 1p reaction, cross section changes smoothly from 370 mb at 12.3 MeV to 160 mb at 18.3 MeV, with a broad peak at 13.5 MeV with the maximum value of 380 mb.[26]
^This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[31]
^This separation is based on that the resulting nuclei move past the target more slowly then the unreacted beam nuclei. The separator contains electric and magnetic fields whose effects on a moving particle cancel out for a specific velocity of a particle.[33] Such separation can also be aided by atime-of-flight measurement and a recoil energy measurement; a combination of the two may allow to estimate the mass of a nucleus.[34]
^It was already known by the 1960s that ground states of nuclei differed in energy and shape as well as that certain magic numbers of nucleons corresponded to greater stability of a nucleus. However, it was assumed that there was no nuclear structure in superheavy nuclei as they were too deformed to form one.[46]
^Since mass of a nucleus is not measured directly but is rather calculated from that of another nucleus, such measurement is called indirect. Direct measurements are also possible, but for the most part they have remained unavailable for superheavy nuclei.[51] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[52] Mass was determined from the location of a nucleus after the transfer (the location helps determine its trajectory, which is linked to the mass-to-charge ratio of the nucleus, since the transfer was done in presence of a magnet).[53]
^If the decay occurred in a vacuum, then since total momentum of an isolated system before and after the decaymust be preserved, the daughter nucleus would also receive a small velocity. The ratio of the two velocities, and accordingly the ratio of the kinetic energies, would thus be inverse to the ratio of the two masses. The decay energy equals the sum of the known kinetic energy of the alpha particle and that of the daughter nucleus (an exact fraction of the former).[42] The calculations hold for an experiment as well, but the difference is that the nucleus does not move after the decay because it is tied to the detector.
^Spontaneous fission was discovered by Soviet physicistGeorgy Flerov,[54] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[55] In contrast, the LBL scientists believed fission information was not sufficient for a claim of synthesis of an element. They believed spontaneous fission had not been studied enough to use it for identification of a new element, since there was a difficulty of establishing that a compound nucleus had only ejected neutrons and not charged particles like protons or alpha particles.[31] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[54]
^For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics inStockholm,Stockholm County,Sweden.[56] There were no earlier definitive claims of creation of this element, and the element was assigned a name by its Swedish, American, and British discoverers,nobelium. It was later shown that the identification was incorrect.[57] The following year, RL was unable to reproduce the Swedish results and announced instead their synthesis of the element; that claim was also disproved later.[57] JINR insisted that they were the first to create the element and suggested a name of their own for the new element,joliotium;[58] the Soviet name was also not accepted (JINR later referred to the naming of the element 102 as "hasty").[59] This name was proposed to IUPAC in a written response to their ruling on priority of discovery claims of elements, signed 29 September 1992.[59] The name "nobelium" remained unchanged on account of its widespread usage.[60]
^In Russian, Oganessian's name is spelled Оганесян[ˈɐgənʲɪˈsʲan]; the transliteration in accordance with the rules of the English language would beOganesyan, with one s. Similarly, the Russian name for the element is оганесон, letter-for-letteroganeson.Oganessian is the Russified version of the Armenian last nameHovhannisyan (Armenian:Հովհաննիսյան[hɔvhɑnnisˈjɑn]).It means "son ofHovhannes", i.e., "son of John".It is one of themost common surnames in Armenia.
^abcdHoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.).The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands:Springer Science+Business Media.ISBN978-1-4020-3555-5.
^abcdGuo, Yangyang; Pašteka, Lukáš F.; Eliav, Ephraim; Borschevsky, Anastasia (2021). "Chapter 5: Ionization potentials and electron affinity of oganesson with relativistic coupled cluster method". In Musiał, Monika; Hoggan, Philip E. (eds.).Advances in Quantum Chemistry. Vol. 83. pp. 107–123.ISBN978-0-12-823546-1.
^abcdGrosse, A. V. (1965). "Some physical and chemical properties of element 118 (Eka-Em) and element 86 (Em)".Journal of Inorganic and Nuclear Chemistry.27 (3). Elsevier Science Ltd.:509–19.doi:10.1016/0022-1902(65)80255-X.
^"Популярная библиотека химических элементов. Сиборгий (экавольфрам)" [Popular library of chemical elements. Seaborgium (eka-tungsten)].n-t.ru (in Russian). Retrieved7 January 2020. Reprinted from"Экавольфрам" [Eka-tungsten].Популярная библиотека химических элементов. Серебро – Нильсборий и далее [Popular library of chemical elements. Silver through nielsbohrium and beyond] (in Russian).Nauka. 1977.
^abMoody, Ken (30 November 2013). "Synthesis of Superheavy Elements". In Schädel, Matthias; Shaughnessy, Dawn (eds.).The Chemistry of Superheavy Elements (2nd ed.). Springer Science & Business Media. pp. 24–8.ISBN978-3-642-37466-1.
^abVoinov, A. A.; Oganessian, Yu. Ts; Abdullin, F. Sh.; Brewer, N. T.; Dmitriev, S. N.; Grzywacz, R. K.; Hamilton, J. H.; Itkis, M. G.; Miernik, K.; Polyakov, A. N.; Roberto, J. B.; Rykaczewski, K. P.; Sabelnikov, A. V.; Sagaidak, R. N.; Shriokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V. K.; Vostokin, G. K. (2016). "Results from the Recent Study of the249–251Cf +48Ca Reactions". In Peninozhkevich, Yu. E.; Sobolev, Yu. G. (eds.).Exotic Nuclei: EXON-2016 Proceedings of the International Symposium on Exotic Nuclei. Exotic Nuclei. pp. 219–223.ISBN978-981-322-655-5.
^abTarasevich, Grigoriy; Lapenko, Igor (2019). "Юрий Оганесян о тайнах ядра, новых элементах и смысле жизни" [Yuri Oganessian about the secret of the nucleus, new elements and the meaning of life].Kot Shryodingyera (in Russian). No. Special. Direktsiya Festivalya Nauki. p. 22.
^abGoidenko, Igor; Labzowsky, Leonti; Eliav, Ephraim; Kaldor, Uzi; Pyykkö, Pekka (2003). "QED corrections to the binding energy of the eka-radon (Z=118) negative ion".Physical Review A.67 (2): 020102(R).Bibcode:2003PhRvA..67b0102G.doi:10.1103/PhysRevA.67.020102.
^Borschevsky, Anastasia; Pershina, Valeria; Eliav, Ephraim; Kaldor, Uzi (27 August 2009). "Electron affinity of element 114, with comparison to Sn and Pb".Chemical Physics Letters.480 (1):49–51.Bibcode:2009CPL...480...49B.doi:10.1016/j.cplett.2009.08.059.
^Nash, Clinton S.; Bursten, Bruce E. (1999). "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".Journal of Physical Chemistry A.1999 (3):402–410.Bibcode:1999JPCA..103..402N.doi:10.1021/jp982735k.PMID27676357.
^abHan, Young-Kyu; Lee, Yoon Sup (1999). "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)F4".Journal of Physical Chemistry A.103 (8):1104–1108.Bibcode:1999JPCA..103.1104H.doi:10.1021/jp983665k.
^Liebman, Joel F. (1975). "Conceptual Problems in Noble Gas and Fluorine Chemistry, II: The Nonexistence of Radon Tetrafluoride".Inorg. Nucl. Chem. Lett.11 (10):683–685.doi:10.1016/0020-1650(75)80185-1.
