Copernicium is calculated to have several properties that differ from its lighterhomologues in group 12,zinc,cadmium andmercury; due torelativistic effects, it may give up its 6d electrons instead of its 7s ones, and it may have more similarities to thenoble gases such asradon rather than its group 12 homologues. Calculations indicate that copernicium may show theoxidation state +4, while mercury shows it inonly one compound of disputed existence and zinc and cadmium do not show it at all. It has also been predicted to be more difficult to oxidize copernicium from its neutral state than the other group 12 elements. Predictions vary on whether solid copernicium would be a metal, semiconductor, or insulator. Copernicium is one of the heaviest elements whose chemical properties have been experimentally investigated.
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.[16] 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.[17] 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.[17]
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.[17][18] This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.[17] 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.[17]
The resulting merger is anexcited state[21]—termed acompound nucleus—and thus it is very unstable.[17] To reach a more stable state, the temporary merger mayfission without formation of a more stable nucleus.[22] 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.[22] 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.[23][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.[25] 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.[25] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[28] The nucleus is recorded again once its decay is registered, and the location, theenergy, and the time of the decay are measured.[25]
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.[29] 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.[30][31] Superheavy nuclei are thus theoretically predicted[32] and have so far been observed[33] 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,[35] and the lightest nuclide primarily undergoing spontaneous fission has 238.[36] In both decay modes, nuclei are inhibited from decaying by correspondingenergy barriers for each mode, but they can be tunneled through.[30][31]
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.[37]
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.[38] Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning.[31] 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),[39] and by 30 orders of magnitude fromthorium (element 90) tofermium (element 100).[40] 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.[31][41] 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.[31][41] 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.[42] Experiments on lighter superheavy nuclei,[43] as well as those closer to the expected island,[39] 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.)[25] 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]
In May 2000, the GSI successfully repeated the experiment to synthesize a further atom of copernicium-277.[55]This reaction was repeated atRIKEN using the Search for a Super-Heavy Element Using a Gas-Filled Recoil Separator set-up in 2004 and 2013 to synthesize three further atoms and confirm the decay data reported by the GSI team.[56][57] This reaction had also previously been tried in 1971 at theJoint Institute for Nuclear Research inDubna,Russia, to aim for276Cn (produced in the 2n channel), but without success.[58]
TheIUPAC/IUPAP Joint Working Party (JWP) assessed the claim of copernicium's discovery by the GSI team in 2001[59] and 2003.[60] In both cases, they found that there was insufficient evidence to support their claim. This was primarily related to the contradicting decay data for the knownnuclide rutherfordium-261. However, between 2001 and 2005, the GSI team studied the reaction248Cm(26Mg,5n)269Hs, and were able to confirm the decay data forhassium-269 andrutherfordium-261. It was found that the existing data on rutherfordium-261 was for anisomer,[61] now designated rutherfordium-261m.
In May 2009, the JWP reported on the claims of discovery of element 112 again and officially recognized the GSI team as the discoverers of element 112.[62] This decision was based on the confirmation of the decay properties of daughter nuclei as well as the confirmatory experiments at RIKEN.[63]
Work had also been done at theJoint Institute for Nuclear Research inDubna, Russia from 1998 to synthesize the heavier isotope283Cn in the hot fusion reaction238U(48Ca,3n)283Cn; most observed atoms of283Cn decayed by spontaneous fission, although an alpha decay branch to279Ds was detected. While initial experiments aimed to assign the produced nuclide with its observed long half-life of 3 minutes based on its chemical behaviour, this was found to be not mercury-like as would have been expected (copernicium being under mercury in the periodic table),[63] and indeed now it appears that the long-lived activity might not have been from283Cn at all, but itselectron capture daughter283Rg instead, with a shorter 4-second half-life associated with283Cn. (Another possibility is assignment to ametastable isomeric state,283mCn.)[64] While later cross-bombardments in the242Pu+48Ca and245Cm+48Ca reactions succeeded in confirming the properties of283Cn and its parents287Fl and291Lv, and played a major role in the acceptance of the discoveries offlerovium andlivermorium (elements 114 and 116) by the JWP in 2011, this work originated subsequent to the GSI's work on277Cn and priority was assigned to the GSI.[63]
Nicolaus Copernicus, who formulated a heliocentric model with the planets orbiting around the Sun, replacingPtolemy's earlier geocentric model
UsingMendeleev's nomenclature for unnamed and undiscovered elements, copernicium should be known aseka-mercury. In 1979, IUPAC published recommendations according to which the element was to be calledununbium (with the corresponding symbol ofUub),[65] asystematic element name as aplaceholder, until the element was discovered (and the discovery then confirmed) and a permanent name was decided on. 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 either called it "element 112", with the symbol ofE112,(112), or even simply112.[1]
After acknowledging the GSI team's discovery, theIUPAC asked them to suggest a permanent name for element 112.[63][66] On 14 July 2009, they proposedcopernicium with the element symbol Cp, afterNicolaus Copernicus "to honor an outstanding scientist, who changed our view of the world".[67]
During the standard six-month discussion period among the scientific community about the naming,[68][69]it was pointed out that the symbolCp was previously associated with the namecassiopeium (cassiopium), now known aslutetium (Lu).[70][71] Moreover, Cp is frequently used today to mean thecyclopentadienyl ligand (C5H5).[72] Primarily because cassiopeium (Cp) was (until 1949) accepted by IUPAC as an alternative allowed name for lutetium,[73] the IUPAC disallowed the use of Cp as a future symbol, prompting the GSI team to put forward the symbol Cn as an alternative. On 19 February 2010, the 537th anniversary of Copernicus' birth, IUPAC officially accepted the proposed name and symbol.[68][74]
Copernicium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Eight different isotopes have been reported with mass numbers 277 and 280–286, and one unconfirmedmetastable isomer in285Cn has been reported.[79] Most of these decay predominantly through alpha decay, but some undergospontaneous fission, and copernicium-283 may have anelectron capture branch.[80]
The isotope copernicium-283 was instrumental in the confirmation of the discoveries of the elementsflerovium andlivermorium.[81]
All confirmed copernicium isotopes are extremely unstable and radioactive; in general, heavier isotopes are more stable than the lighter, and isotopes with anodd neutron number have relatively longer half-lives due to additional hindrance againstspontaneous fission. The most stable known isotope,285Cn, has a half-life of 30 seconds;283Cn has a half-life of 4 seconds, and the unconfirmed285mCn and286Cn have half-lives of about 15 and 8.45 seconds respectively. Other isotopes have half-lives shorter than one second.281Cn and284Cn both have half-lives on the order of 0.1 seconds, and the remaining isotopes have half-lives shorter than one millisecond.[80] It is predicted that the heavy isotopes291Cn and293Cn may have half-lives longer than a few decades, for they are predicted to lie near the center of the theoreticalisland of stability, and may have been produced in ther-process and be detectable incosmic rays, though they would be about 10−12 times as abundant aslead.[82]
The lightest isotopes of copernicium have been synthesized by direct fusion between two lighter nuclei and asdecay products (except for277Cn, which is not known to be a decay product), while the heavier isotopes are only known to be produced by decay of heavier nuclei. The heaviest isotope produced by direct fusion is283Cn; the three heavier isotopes,284Cn,285Cn, and286Cn, have only been observed as decay products of elements with larger atomic numbers.[80]
In 1999, American scientists at the University of California, Berkeley, announced that they had succeeded in synthesizing three atoms of293Og.[83] These parent nuclei were reported to have successively emitted three alpha particles to form copernicium-281 nuclei, which were claimed to have undergone alpha decay, emitting alpha particles with decay energy 10.68 MeV and half-life 0.90 ms, but their claim was retracted in 2001[84] as it had been based on data fabricated by Ninov.[85] This isotope was truly produced in 2010 by the same team; the new data contradicted the previous fabricated data.[86]
The missing isotopes278Cn and279Cn are too heavy to be produced by cold fusion and too light to be produced by hot fusion.[82] They might be filled from above by decay of heavier elements produced by hot fusion,[82] and indeed280Cn and281Cn were produced this way.[75][86] The isotopes286Cn and287Cn could be produced by charged-particle evaporation, in the reaction244Pu(48Ca,αxn) withx equalling 1 or 2.[87][88]
Very few properties of copernicium or its compounds have been measured; this is due to its extremely limited and expensive production[89] and the fact that copernicium (and its parents) decays very quickly. A few singular chemical properties have been measured, as well as the boiling point, but properties of the copernicium metal remain generally unknown and for the most part, only predictions are available.
Copernicium is the tenth and last member of the 6d series and is the heaviestgroup 12 element in the periodic table, belowzinc,cadmium andmercury. It is predicted to differ significantly from the lighter group 12 elements. The valence s-subshells of the group 12 elements and period 7 elements are expected to be relativistically contracted most strongly at copernicium. This and the closed-shell configuration of copernicium result in it probably being a verynoble metal. Astandard reduction potential of +2.1 V is predicted for the Cn2+/Cn couple. Copernicium's predicted first ionization energy of 1155 kJ/mol almost matches that of the noble gasxenon at 1170.4 kJ/mol.[1] Copernicium'smetallic bonds should also be very weak, possibly making it extremely volatile like the noble gases, and potentially making it gaseous at room temperature.[1][90] However, it should be able to form metal–metal bonds withcopper,palladium,platinum,silver, andgold; these bonds are predicted to be only about 15–20 kJ/mol weaker than the analogous bonds with mercury.[1] In opposition to the earlier suggestion,[91] ab initio calculations at the high level of accuracy[92] predicted that the chemistry of singly-valent copernicium resembles that of mercury rather than that of the noble gases. The latter result can be explained by the hugespin–orbit interaction which significantly lowers the energy of the vacant 7p1/2 state of copernicium.
Once copernicium is ionized, its chemistry may present several differences from those of zinc, cadmium, and mercury. Due to the stabilization of 7s electronic orbitals and destabilization of 6d ones caused byrelativistic effects, Cn2+ is likely to have a [Rn]5f146d87s2electronic configuration, using the 6d orbitals before the 7s one, unlike its homologues. The fact that the 6d electrons participate more readily in chemical bonding means that once copernicium is ionized, it may behave more like atransition metal than its lighterhomologues, especially in the possible +4 oxidation state. Inaqueous solutions, copernicium may form the +2 and perhaps +4 oxidation states.[1] The diatomic ionHg2+ 2, featuring mercury in the +1 oxidation state, is well-known, but theCn2+ 2 ion is predicted to be unstable or even non-existent.[1] Copernicium(II) fluoride, CnF2, should be more unstable than the analogous mercury compound,mercury(II) fluoride (HgF2), and may even decompose spontaneously into its constituent elements. As the most electronegative reactive element, fluorine may be the only element able to oxidize copernicium even further to the +4 and even +6 oxidation states in CnF4 and CnF6; the latter may require matrix-isolation conditions to be detected, as in the disputed detection ofHgF4. CnF4 should be more stable than CnF2.[93] Inpolar solvents, copernicium is predicted to preferentially form theCnF− 5 andCnF− 3 anions rather than the analogous neutral fluorides (CnF4 and CnF2, respectively), although the analogous bromide or iodide ions may be more stable towardshydrolysis in aqueous solution. The anionsCnCl2− 4 andCnBr2− 4 should also be able to exist in aqueous solution.[1] The formation of thermodynamically stable copernicium(II) and (IV) fluorides would be analogous to the chemistry of xenon.[3] Analogous tomercury(II) cyanide (Hg(CN)2), copernicium is expected to form a stablecyanide, Cn(CN)2.[94]
Copernicium should be a dense metal, with adensity of 14.0 g/cm3 in the liquid state at 300 K; this is similar to the known density of mercury, which is 13.534 g/cm3. (Solid copernicium at the same temperature should have a higher density of 14.7 g/cm3.) This results from the effects of copernicium's higher atomic weight being cancelled out by its larger interatomic distances compared to mercury.[3] Some calculations predicted copernicium to be a gas at room temperature due to its closed-shell electron configuration,[95] which would make it the first gaseous metal in the periodic table.[1][90] A 2019 calculation agrees with these predictions on the role of relativistic effects, suggesting that copernicium will be a volatile liquid bound bydispersion forces under standard conditions. Its melting point is estimated at283±11 K and its boiling point at340±10 K, the latter in agreement with the experimentally estimated value of357+112 −108 K.[3] The atomic radius of copernicium is expected to be around 147 pm. Due to the relativistic stabilization of the 7s orbital and destabilization of the 6d orbital, the Cn+ and Cn2+ ions are predicted to give up 6d electrons instead of 7s electrons, which is the opposite of the behavior of its lighter homologues.[1]
In addition to the relativistic contraction and binding of the 7s subshell, the 6d5/2 orbital is expected to be destabilized due tospin–orbit coupling, making it behave similarly to the 7s orbital in terms of size, shape, and energy. Predictions of the expected band structure of copernicium are varied. Calculations in 2007 expected that copernicium may be asemiconductor[96] with aband gap of around 0.2 eV,[97] crystallizing in thehexagonal close-packedcrystal structure.[97] However, calculations in 2017 and 2018 suggested that copernicium should be anoble metal at standard conditions with abody-centered cubic crystal structure: it should hence have no band gap, like mercury, although the density of states at theFermi level is expected to be lower for copernicium than for mercury.[98][99] 2019 calculations then suggested that in fact copernicium has a large band gap of 6.4 ± 0.2 eV, which should be similar to that of the noble gasradon (predicted as 7.1 eV) and would make it an insulator; bulk copernicium is predicted by these calculations to be bound mostly bydispersion forces, like the noble gases.[3] Like mercury, radon, and flerovium, but notoganesson (eka-radon), copernicium is calculated to have noelectron affinity.[100]
Interest in copernicium's chemistry was sparked by predictions that it would have the largest relativistic effects in the whole of period 7 and group 12, and indeed among all 118 known elements.[1] Copernicium is expected to have the ground state electron configuration [Rn] 5f14 6d10 7s2 and thus should belong to group 12 of the periodic table, according to theAufbau principle. As such, it should behave as the heavier homologue ofmercury and form strong binary compounds withnoble metals like gold. Experiments probing the reactivity of copernicium have focused on theadsorption of atoms of element 112 onto a gold surface held at varying temperatures, in order to calculate an adsorption enthalpy. Owing to relativistic stabilization of the 7s electrons, copernicium shows radon-like properties. Experiments were performed with the simultaneous formation of mercury and radon radioisotopes, allowing a comparison of adsorption characteristics.[101]
The first chemical experiments on copernicium were conducted using the238U(48Ca,3n)283Cn reaction. Detection was by spontaneous fission of the claimed parent isotope with half-life of 5 minutes. Analysis of the data indicated that copernicium was more volatile than mercury and had noble gas properties. However, the confusion regarding the synthesis of copernicium-283 has cast some doubt on these experimental results.[101] Given this uncertainty, between April–May 2006 at the JINR, a FLNR–PSI team conducted experiments probing the synthesis of this isotope as a daughter in the nuclear reaction242Pu(48Ca,3n)287Fl.[101] (The242Pu +48Ca fusion reaction has a slightly larger cross-section than the238U +48Ca reaction, so that the best way to produce copernicium for chemical experimentation is as an overshoot product as the daughter of flerovium.)[102] In this experiment, two atoms of copernicium-283 were unambiguously identified and the adsorption properties were interpreted to show that copernicium is a more volatile homologue of mercury, due to formation of a weak metal-metal bond with gold.[101] This agrees with general indications from some relativistic calculations that copernicium is "more or less" homologous to mercury.[103] However, it was pointed out in 2019 that this result may simply be due to strong dispersion interactions.[3]
In April 2007, this experiment was repeated and a further three atoms of copernicium-283 were positively identified. The adsorption property was confirmed and indicated that copernicium has adsorption properties in agreement with being the heaviest member of group 12.[101] These experiments also allowed the first experimental estimation of copernicium's boiling point: 84+112 −108 °C, so that it may be a gas at standard conditions.[96]
Because the lighter group 12 elements often occur aschalcogenide ores, experiments were conducted in 2015 to deposit copernicium atoms on aselenium surface to form copernicium selenide, CnSe. Reaction of copernicium atoms with trigonal selenium to form a selenide was observed, with -ΔHadsCn(t-Se) > 48 kJ/mol, with the kinetic hindrance towards selenide formation being lower for copernicium than for mercury. This was unexpected as the stability of the group 12 selenides tends to decrease down the group fromZnSe toHgSe.[104]
^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[11] or 112;[12] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypotheticalsuperactinide series).[13] 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.[14] 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.[15]
^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.[19]
^This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[24]
^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.[26] 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.[27]
^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.[39]
^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.[44] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[45] 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).[46]
^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).[35] 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,[47] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[48] 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.[24] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[47]
^For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics inStockholm,Stockholm County,Sweden.[49] 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.[50] 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.[50] JINR insisted that they were the first to create the element and suggested a name of their own for the new element,joliotium;[51] the Soviet name was also not accepted (JINR later referred to the naming of the element 102 as "hasty").[52] This name was proposed to IUPAC in a written response to their ruling on priority of discovery claims of elements, signed 29 September 1992.[52] The name "nobelium" remained unchanged on account of its widespread usage.[53]
^Different sources give different values for half-lives; the most recently published values are listed.
^abcdefghijklmnHoffman, 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.
^"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.
^Morita, K. (2004). "Decay of an Isotope277112 produced by208Pb +70Zn reaction". In Penionzhkevich, Yu. E.; Cherepanov, E. A. (eds.).Exotic Nuclei: Proceedings of the International Symposium.World Scientific. pp. 188–191.doi:10.1142/9789812701749_0027.
^Sumita, Takayuki; Morimoto, Kouji; Kaji, Daiya; Haba, Hiromitsu; Ozeki, Kazutaka; Sakai, Ryutaro; Yoneda, Akira; Yoshida, Atsushi; Hasebe, Hiroo; Katori, Kenji; Sato, Nozomi; Wakabayashi, Yasuo; Mitsuoka, Shin-Ichi; Goto, Shin-Ichi; Murakami, Masashi; Kariya, Yoshiki; Tokanai, Fuyuki; Mayama, Keita; Takeyama, Mirei; Moriya, Toru; Ideguchi, Eiji; Yamaguchi, Takayuki; Kikunaga, Hidetoshi; Chiba, Junsei; Morita, Kosuke (2013). "New Result on the Production of277Cn by the208Pb +70Zn Reaction".Journal of the Physical Society of Japan.82 (2) 024202.Bibcode:2013JPSJ...82b4202S.doi:10.7566/JPSJ.82.024202.
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