Unbibium

\( \require{mhchem} \)

Unbibium, also known as element 122 or eka-thorium, is a hypothetical chemical element; it has placeholder symbol Ubb and atomic number 122. Unbibium and Ubb are the temporary systematic IUPAC name and symbol respectively, which are used until the element is discovered, confirmed, and a permanent name is decided upon. In the periodic table of the elements, it is expected to follow unbiunium as the second element of the superactinides and the fourth element of the 8th period. Similarly to unbiunium, it is expected to fall within the range of the island of stability, potentially conferring additional stability on some isotopes, especially 306Ubb which is expected to have a magic number of neutrons (184).

Despite several attempts, unbibium has not yet been synthesized, nor have any naturally occurring isotopes been found to exist. There are currently no plans to attempt to synthesize unbibium. In 2008, it was claimed to have been discovered in natural thorium samples,[3] but that claim has now been dismissed by recent repetitions of the experiment using more accurate techniques.

Chemically, unbibium is expected to show some resemblance to cerium and thorium. However, relativistic effects may cause some of its properties to differ; for example, it is expected to have a ground state electron configuration of [Og] 7d1 8s2 8p1 or [Og] 8s2 8p2, despite its predicted position in the g-block superactinide series.[1]
Introduction

A graphic depiction of a nuclear fusion reaction

External videos
[4]

The heaviest[a] atomic nuclei are created in nuclear reactions that combine two other nuclei of unequal size[b] into one; roughly, the more unequal the two nuclei in terms of mass, the greater the possibility that the two react.[10] The material made of the heavier nuclei is made into a target, which is then bombarded by the beam of lighter nuclei. Two nuclei can fuse into one only if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due to electrostatic repulsion. The strong interaction can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatly accelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus.[11] Coming close alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for approximately 10−20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus.[11][12] If fusion does occur, the temporary merger—termed a compound nucleus—is an excited state. To lose its excitation energy and reach a more stable state, a compound nucleus either fissions or ejects one or several neutrons,[c] which carry away the energy. This occurs in approximately 10−16 seconds after the initial collision.[13][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.[16] 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 a surface-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.[16] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[19] The nucleus is recorded again once its decay is registered, and the location, the energy, and the time of the decay are measured.[16]

Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, their influence on the outermost nucleons (protons and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, as it has unlimited range.[20] Nuclei of the heaviest elements are thus theoretically predicted[21] and have so far been observed[22] to primarily decay via decay modes that are caused by such repulsion: alpha decay and spontaneous fission;[f] these modes are predominant for nuclei of superheavy elements. 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 determined arithmetically.[g] Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters.[h]

The information available to physicists aiming to synthesize one of the heaviest elements 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.[i]
History
Synthesis attempts
Fusion-evaporation

Two attempts were made to synthesize unbibium were in the 1970s, both propelled by early predictions on the island of stability at N = 184 and Z > 120,[34] and in particular whether superheavy elements could potentially be naturally occurring.[35] The first attempts to synthesize unbibium were performed in 1972 by Flerov et al. at the Joint Institute for Nuclear Research (JINR), using the heavy-ion induced hot fusion reactions:[35]

238
92U
+ 66,68
30Zn
→ 304,306
122Ubb
* → no atoms

Another unsuccessful attempt to synthesize unbibium was carried out in 1978 at the GSI Helmholtz Center, where a natural erbium target was bombarded with xenon-136 ions:[35]

nat
68Er
+ 136
54Xe
→ 298,300,302,303,304,306
Ubb
* → no atoms

No atoms were detected and a yield limit of 5 nb (5,000 pb) was measured. Current results (see flerovium) have shown that the sensitivity of these experiments were too low by at least 3 orders of magnitude.[34] In particular, the reaction between 170Er and 136Xe was expected to yield alpha emitters with half-lives of microseconds that would decay down to isotopes of flerovium with half-lives perhaps increasing up to several hours, as flerovium is predicted to lie near the center of the island of stability. After twelve hours of irradiation, nothing was found in this reaction. Following a similar unsuccessful attempt to synthesize unbiunium from 238U and 65Cu, it was concluded that half-lives of superheavy nuclei must be less than one microsecond or the cross sections are very small.[36] More recent research into synthesis of superheavy elements suggests that both conclusions are true.[37][38]

In 2000, the Gesellschaft für Schwerionenforschung (GSI) Helmholtz Center for Heavy Ion Research performed a very similar experiment with much higher sensitivity:[35]

238
92U
+ 70
30Zn
→ 308
122Ubb
* → no atoms

These results indicate that the synthesis of such heavier elements remains a significant challenge and further improvements of beam intensity and experimental efficiency is required. The sensitivity should be increased to 1 fb in the future for more quality results.
Compound nucleus fission

Several experiments studying the fission characteristics of various superheavy compound nuclei such as 306Ubb were performed between 2000 and 2004 at the Flerov Laboratory of Nuclear Reactions. Two nuclear reactions were used, namely 248Cm + 58Fe and 242Pu + 64Ni.[35] The results reveal how superheavy nuclei fission predominantly by expelling closed shell nuclei such as 132Sn (Z = 50, N = 82). It was also found that the yield for the fusion-fission pathway was similar between 48Ca and 58Fe projectiles, suggesting a possible future use of 58Fe projectiles in superheavy element formation.[39]
Claimed discovery as a naturally occurring element

In 2008, a group led by Israeli physicist Amnon Marinov at the Hebrew University of Jerusalem claimed to have found single atoms of unbibium-292 in naturally occurring thorium deposits at an abundance of between 10−11 and 10−12 relative to thorium.[3] This was the first time in 69 years that a new element had been claimed to be discovered in nature, after Marguerite Perey's 1939 discovery of francium.[j] The claim of Marinov et al. was criticized by a part of the scientific community, and Marinov says he has submitted the article to the journals Nature and Nature Physics but both turned it down without sending it for peer review.[40] The unbibium-292 atoms were claimed to be superdeformed or hyperdeformed isomers, with a half-life of at least 100 million years.[35]

A criticism of the technique, previously used in purportedly identifying lighter thorium isotopes by mass spectrometry,[41] was published in Physical Review C in 2008.[42] A rebuttal by the Marinov group was published in Physical Review C after the published comment.[43]

A repeat of the thorium experiment using the superior method of accelerator mass spectrometry (AMS) failed to confirm the results, despite a 100-fold better sensitivity.[44] This result throws considerable doubt on the results of the Marinov collaboration with regards to their claims of long-lived isotopes of thorium,[41] roentgenium,[45] and unbibium.[3] Current understanding of superheavy elements indicates that it is very unlikely for any traces of unbibium to persist in natural thorium samples.[35]
Naming

Using Mendeleev's nomenclature for unnamed and undiscovered elements, unbibium should instead be known as eka-thorium.[46] After the recommendations of the IUPAC in 1979, the element has since been largely referred to as unbibium with the atomic symbol of (Ubb),[47] as its temporary name until the element is officially discovered and synthesized, and a permanent name is decided on. Scientists largely ignore this naming convention, and instead simply refer to unbibium as "element 122" with the symbol of (122), or sometimes even E122 or 122.[48]
Prospects for future synthesis
Predicted decay modes of superheavy nuclei. The line of synthesized proton-rich nuclei is expected to be broken soon after Z = 120, because of the shortening half-lives until around Z = 124, the increasing contribution of spontaneous fission instead of alpha decay from Z = 122 onward until it dominates from Z = 125, and the proton drip line around Z = 130. The white ring denotes the expected location of the island of stability; the two squares outlined in white denote 291Cn and 293Cn, predicted to be the longest-lived nuclides on the island with half-lives of centuries or millennia.[49][37]

Every element from mendelevium onward was produced in fusion-evaporation reactions, culminating in the discovery of the heaviest known element oganesson in 2002[50][51] and most recently tennessine in 2010.[52] These reactions approached the limit of current technology; for example, the synthesis of tennessine required 22 milligrams of 249Bk and an intense 48Ca beam for six months. The intensity of beams in superheavy element research cannot exceed 1012 projectiles per second without damaging the target and detector, and producing larger quantities of increasingly rare and unstable actinide targets is impractical.[53] Consequently, future experiments must be done at facilities such as the superheavy element factory (SHE-factory) at the Joint Institute for Nuclear Research (JINR) or RIKEN, which will allow experiments to run for longer stretches of time with increased detection capabilities and enable otherwise inaccessible reactions.[54]

It is possible that fusion-evaporation reactions will not be suitable for the discovery of unbibium or heavier elements. Various models predict increasingly short alpha and spontaneous fission half-lives for isotopes with Z = 122 and N ~ 180 on the order of microseconds or less,[55] rendering detection nearly impossible with current equipment.[37] The increasing dominance of spontaneous fission also may sever possible ties to known nuclei of livermorium or oganesson and make identification and confirmation more difficult; a similar problem occurred in the road to confirmation of the decay chain of 294Og which has no anchor to known nuclei.[56] For these reasons, other methods of production may need to be researched such as multi-nucleon transfer reactions capable of populating longer-lived nuclei. A similar switch in experimental technique occurred when hot fusion using 48Ca projectiles was used instead of cold fusion (in which cross sections decrease rapidly with increasing atomic number) to populate elements with Z > 113.[38]

Nevertheless, several fusion-evaporation reactions leading to unbibium have been proposed in addition to those already tried unsuccessfully, though no institution has immediate plans to make synthesis attempts, instead focusing first on elements 119, 120, and possibly 121. Because cross sections increase with asymmetry of the reaction,[38] a chromium beam would be most favorable in combination with a californium target,[37] especially if the predicted closed neutron shell at N = 184 could be reached in more neutron-rich products and confer additional stability. In particular, the reaction between 54
24Cr
and 252
98Cf
would generate the compound nucleus 306
122Ubb
and reach the shell at N = 184, though the analogous reaction with a 249
98Cf
target is believed to be more feasible because of the presence of unwanted fission products from 252
98Cf
and difficulty in accumulating the required amount of target material.[57] One possible synthesis of unbibium could occur as follows:[37]

249
98Cf
+ 54
24Cr
→ 300
122Ubb
+ 3 1
0
n

Should this reaction be successful and alpha decay remain dominant over spontaneous fission, the resultant 300Ubb would decay through 296Ubn which may be populated in cross-bombardment between 249Cf and 50Ti. Although this reaction is one of the most promising options for the synthesis of unbibium in the near future, the maximum cross section is predicted to be 3 fb,[57] one order of magnitude lower than the lowest measured cross section in a successful reaction. The more symmetrical reactions 244Pu + 64Ni and 248Cm + 58Fe[37] have also been proposed and may produce more neutron-rich isotopes. With increasing atomic number, one must also be aware of decreasing fission barrier heights, resulting in lower survival probability of compound nuclei, especially above the predicted magic numbers at Z = 126 and N = 184.[57]
Predicted properties
Nuclear stability and isotopes
See also: Island of stability
A 2D graph with rectangular cells colored in black-and-white colors, spanning from the llc to the urc, with cells mostly becoming lighter closer to the latter
A chart of nuclide stability as used by the Dubna team in 2010. Characterized isotopes are shown with borders. Beyond element 118 (oganesson, the last known element), the line of known nuclides is expected to rapidly enter a region of instability, with no half-lives over one microsecond after element 121; this poses difficulties in identifying heavier elements such as unbibium. The elliptical region encloses the predicted location of the island of stability.[38]

The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day. No elements with atomic numbers above 82 (after lead) have stable isotopes.[58] Nevertheless, because of reasons not very well understood yet, there is a slight increased nuclear stability around atomic numbers 110–114, which leads to the appearance of what is known in nuclear physics as the "island of stability". This concept, proposed by University of California professor Glenn Seaborg, explains why superheavy elements last longer than predicted.[59]

In this region of the periodic table, N = 184 has been suggested as a closed neutron shell, and various atomic numbers have been proposed as closed proton shells, such as Z = 114, 120, 122, 124, and 126. The island of stability would be characterized by longer half-lives of nuclei located near these magic numbers, though the extent of stabilizing effects is uncertain due to predictions of weakening of the proton shell closures and possible loss of double magicity.[60] More recent research predicts the island of stability to instead be centered at beta-stable copernicium isotopes 291Cn and 293Cn,[38][61] which would place unbibium well above the island and result in short half-lives regardless of shell effects. The increased stability of elements 112–118 has also been attributed to the oblate shape of such nuclei and resistance to spontaneous fission. The same model also proposes 306Ubb as the next spherical doubly magic nucleus, thus defining the true island of stability for spherical nuclei.[62]
Regions of differently shaped nuclei, as predicted by the Interacting Boson Approximation[62]

A quantum tunneling model predicts the alpha-decay half-lives of unbibium isotopes 284–322Ubb to be on the order of microseconds or less for all isotopes lighter than 315Ubb,[63] highlighting a significant challenge in experimental observation of this element. This is consistent with many predictions, though the exact location of the 1 microsecond border varies by model. Additionally, spontaneous fission is expected to become a major decay mode in this region, with half-lives on the order of femtoseconds predicted for some even–even isotopes[55] due to minimal hindrance resulting from nucleon pairing and loss of stabilizing effects farther away from magic numbers.[57] A 2016 calculation on the half-lives and probable decay chains of isotopes 280–339Ubb yields corroborating results: 280–297Ubb will be proton unbound and possibly decay by proton emission, 298–314Ubb will have alpha half-lives on the order of microseconds, and those heavier than 314Ubb will predominantly decay by spontaneous fission with short half-lives.[64] For the lighter alpha emitters that may be populated in fusion-evaporation reactions, some long decay chains leading down to known or reachable isotopes of lighter elements are predicted. Additionally, the isotopes 308–310Ubb are predicted to have half-lives under 1 microsecond,[55][64] too short for detection as a result of significantly lower binding energy for neutron numbers immediately above the N = 184 shell closure. Alternatively, a second island of stability with total half-lives of approximately 1 second may exist around Z ~ 124 and N ~ 198, though these nuclei will be difficult or impossible to reach using current experimental techniques.[61] However, these predictions are strongly dependent on the chosen nuclear mass models, and it is unknown which isotopes of unbibium will be most stable. Regardless, these nuclei will be hard to synthesize as no combination of obtainable target and projectile can provide enough neutrons in the compound nucleus. Even for nuclei reachable in fusion reactions, spontaneous fission and possibly also cluster decay[65] might have significant branches, posing another hurdle to identification of superheavy elements as they are normally identified by their successive alpha decays.
Chemical

Unbibium is predicted to be similar in chemistry to cerium and thorium, which likewise have four valence electrons above a noble gas core, although it may be more reactive. Additionally, unbibium is predicted to belong to a new block of valence g-electron atoms, although the 5g orbital is not expected to start filling until about element 125. The predicted ground-state electron configuration of unbibium is either [Og] 7d1 8s2 8p1[1][66] or 8s2 8p2,[67] in contrast to the expected [Og] 5g2 8s2 in which the 5g orbital starts filling at element 121. (The ds2p and s2p2 configurations are expected to be only separated by about 0.02 eV.)[67] In the superactinides, relativistic effects might cause a breakdown of the Aufbau principle and create overlapping of the 5g, 6f, 7d and 8p orbitals;[68] experiments on the chemistry of copernicium and flerovium provide strong indications of the increasing role of relativistic effects. As such, the chemistry of elements following unbibium becomes more difficult to predict.

Unbibium would most likely form a dioxide, UbbO2, and tetrahalides, such as UbbF4 and UbbCl4.[1] The main oxidation state is predicted to be +4, similar to cerium and thorium.[35] A first ionization energy of 5.651 eV and second ionization energy of 11.332 eV are predicted for unbibium; this and other calculated ionization energies are lower than the analogous values for thorium, suggesting that unbibium will be more reactive than thorium.[66][2]
Notes

In nuclear physics, an element is called heavy 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 than 103 (although there are other definitions, such as atomic number greater than 100[5] or 112;[6] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypothetical superactinide series).[7] 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 JINR led by Oganessian published results of their attempt to create hassium in a symmetric 136Xe + 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.[8] 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.[9]
The greater the excitation energy, the more neutrons are ejected. If the excitation energy is lower than energy binding each neutron to the rest of the nucleus, neutrons are not emitted; instead, the compound nucleus de-excites by emitting a gamma ray.[13]
The definition by the IUPAC/IUPAP Joint Working Party states that a chemical element can only be recognized as discovered if a nucleus of it has not decayed within 10−14 seconds. This value was chosen as an estimate of how long it takes a nucleus to acquire its outer electrons and thus display its chemical properties.[14] This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[15]
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.[17] Such separation can also be aided by a time-of-flight measurement and a recoil energy measurement; a combination of the two may allow to estimate the mass of a nucleus.[18]
Not all decay modes are caused by electrostatic repulsion. For example, beta decay is caused by the weak interaction.[23]
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 heaviest nuclei.[24] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[25] 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).[26]
Spontaneous fission was discovered by Soviet physicist Georgy Flerov,[27] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[28] 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.[15] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[27]
For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics in Stockholm, Stockholm County, Sweden.[29] 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.[30] The following year, LBNL was unable to reproduce the Swedish results and announced instead their synthesis of the element; that claim was also disproved later.[30] JINR insisted that they were the first to create the element and suggested a name of their own for the new element, joliotium;[31] the Soviet name was also not accepted (JINR later referred to the naming of element 102 as "hasty").[32] The name "nobelium" remained unchanged on account of its widespread usage.[33]

Four more elements were discovered after 1939 through synthesis, but were later found to also occur naturally: these were promethium, astatine, neptunium, and plutonium, all of which had been found by 1945.

References

Pyykkö, Pekka (2011). "A suggested periodic table up to Z ≤ 172, based on Dirac–Fock calculations on atoms and ions". Physical Chemistry Chemical Physics. 13 (1): 161–8. Bibcode:2011PCCP...13..161P. doi:10.1039/c0cp01575j. PMID 20967377.
Eliav, E.; Fritzsche, S.; Kaldor, U. (2015). "Electronic structure theory of the superheavy elements". Nuclear Physics A. 944 (December 2015): 518–550. doi:10.1016/j.nuclphysa.2015.06.017.
Marinov, A.; Rodushkin, I.; Kolb, D.; et al. (2010). "Evidence for a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th". International Journal of Modern Physics E. 19 (1): 131–140. arXiv:0804.3869. Bibcode:2010IJMPE..19..131M. doi:10.1142/S0218301310014662. S2CID 117956340.
Wakhle, A.; Simenel, C.; Hinde, D. J.; et al. (2015). Simenel, C.; Gomes, P. R. S.; Hinde, D. J.; et al. (eds.). "Comparing Experimental and Theoretical Quasifission Mass Angle Distributions". European Physical Journal Web of Conferences. 86: 00061. Bibcode:2015EPJWC..8600061W. doi:10.1051/epjconf/20158600061. ISSN 2100-014X.
Krämer, K. (2016). "Explainer: superheavy elements". Chemistry World. Retrieved 2020-03-15.
"Discovery of Elements 113 and 115". Lawrence Livermore National Laboratory. Archived from the original on 2015-09-11. Retrieved 2020-03-15.
Eliav, E.; Kaldor, U.; Borschevsky, A. (2018). "Electronic Structure of the Transactinide Atoms". In Scott, R. A. (ed.). Encyclopedia of Inorganic and Bioinorganic Chemistry. John Wiley & Sons. pp. 1–16. doi:10.1002/9781119951438.eibc2632. ISBN 978-1-119-95143-8. S2CID 127060181.
Oganessian, Yu. Ts.; Dmitriev, S. N.; Yeremin, A. V.; et al. (2009). "Attempt to produce the isotopes of element 108 in the fusion reaction 136Xe + 136Xe". Physical Review C. 79 (2): 024608. doi:10.1103/PhysRevC.79.024608. ISSN 0556-2813.
Münzenberg, G.; Armbruster, P.; Folger, H.; et al. (1984). "The identification of element 108" (PDF). Zeitschrift für Physik A. 317 (2): 235–236. Bibcode:1984ZPhyA.317..235M. doi:10.1007/BF01421260. S2CID 123288075. Archived from the original (PDF) on 7 June 2015. Retrieved 20 October 2012.
Subramanian, S. (2019). "Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist". Bloomberg Businessweek. Archived from the original on November 14, 2020. Retrieved 2020-01-18.
Ivanov, D. (2019). "Сверхтяжелые шаги в неизвестное" [Superheavy steps into the unknown]. N+1 (in Russian). Retrieved 2020-02-02.
Hinde, D. (2014). "Something new and superheavy at the periodic table". The Conversation. Retrieved 2020-01-30.
Krása, A. (2010). "Neutron Sources for ADS" (PDF). Czech Technical University in Prague. pp. 4–8. S2CID 28796927. Archived from the original (PDF) on 2019-03-03. Retrieved October 20, 2019.
Wapstra, A. H. (1991). "Criteria that must be satisfied for the discovery of a new chemical element to be recognized" (PDF). Pure and Applied Chemistry. 63 (6): 883. doi:10.1351/pac199163060879. ISSN 1365-3075. S2CID 95737691. Retrieved 2020-08-28.
Hyde, E. K.; Hoffman, D. C.; Keller, O. L. (1987). "A History and Analysis of the Discovery of Elements 104 and 105". Radiochimica Acta. 42 (2): 67–68. doi:10.1524/ract.1987.42.2.57. ISSN 2193-3405. S2CID 99193729.
Chemistry World (2016). "How to Make Superheavy Elements and Finish the Periodic Table [Video]". Scientific American. Retrieved 2020-01-27.
Hoffman, Ghiorso & Seaborg 2000, p. 334.
Hoffman, Ghiorso & Seaborg 2000, p. 335.
Zagrebaev, Karpov & Greiner 2013, p. 3.
Beiser 2003, p. 432.
Staszczak, A.; Baran, A.; Nazarewicz, W. (2013). "Spontaneous fission modes and lifetimes of superheavy elements in the nuclear density functional theory". Physical Review C. 87 (2): 024320–1. arXiv:1208.1215. Bibcode:2013PhRvC..87b4320S. doi:10.1103/physrevc.87.024320. ISSN 0556-2813. S2CID 118134429.
Audi, G.; Kondev, F. G.; Wang, M.; et al. (2017). "The NUBASE2016 evaluation of nuclear properties". Chinese Physics C. 41 (3): 030001-128–030001-138. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
Beiser 2003, p. 439.
Oganessian, Yu. Ts.; Rykaczewski, K. P. (2015). "A beachhead on the island of stability". Physics Today. 68 (8): 32–38. Bibcode:2015PhT....68h..32O. doi:10.1063/PT.3.2880. ISSN 0031-9228. OSTI 1337838. S2CID 119531411.
Grant, A. (2018). "Weighing the heaviest elements". Physics Today. doi:10.1063/PT.6.1.20181113a. S2CID 239775403.
Howes, L. (2019). "Exploring the superheavy elements at the end of the periodic table". Chemical & Engineering News. Retrieved 2020-01-27.
Robinson, A. E. (2019). "The Transfermium Wars: Scientific Brawling and Name-Calling during the Cold War". Distillations. Retrieved 2020-02-22.
"Популярная библиотека химических элементов. Сиборгий (экавольфрам)" [Popular library of chemical elements. Seaborgium (eka-tungsten)]. n-t.ru (in Russian). Retrieved 2020-01-07. 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.
"Nobelium – Element information, properties and uses | Periodic Table". Royal Society of Chemistry. Retrieved 2020-03-01.
Kragh 2018, pp. 38–39.
Kragh 2018, p. 40.
Ghiorso, A.; Seaborg, G. T.; Oganessian, Yu. Ts.; et al. (1993). "Responses on the report 'Discovery of the Transfermium elements' followed by reply to the responses by Transfermium Working Group" (PDF). Pure and Applied Chemistry. 65 (8): 1815–1824. doi:10.1351/pac199365081815. S2CID 95069384. Archived (PDF) from the original on 25 November 2013. Retrieved 7 September 2016.
Commission on Nomenclature of Inorganic Chemistry (1997). "Names and symbols of transfermium elements (IUPAC Recommendations 1997)" (PDF). Pure and Applied Chemistry. 69 (12): 2471–2474. doi:10.1351/pac199769122471.
Epherre, M.; Stephan, C. (1975). "Les éléments superlourds" (PDF). Le Journal de Physique Colloques (in French). 11 (36): C5–159–164. doi:10.1051/jphyscol:1975541.
Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. p. 588. ISBN 978-0-19-960563-7.
Hofmann, Sigurd (2014). On Beyond Uranium: Journey to the End of the Periodic Table. CRC Press. p. 105. ISBN 978-0415284950.
Karpov, A; Zagrebaev, V; Greiner, W (2015). "Superheavy Nuclei: which regions of nuclear map are accessible in the nearest studies" (PDF). cyclotron.tamu.edu. Texas A & M University. Retrieved 30 October 2018.
Zagrebaev, Karpov & Greiner 2013
see Flerov lab annual reports 2000–2004 inclusive http://www1.jinr.ru/Reports/Reports_eng_arh.html
Richard Van Noorden (2 May 2008). "Heaviest element claim criticised". Chemical World.
Marinov, A.; Rodushkin, I.; Kashiv, Y.; et al. (2007). "Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes". Phys. Rev. C. 76 (2). 021303(R). arXiv:nucl-ex/0605008. Bibcode:2007PhRvC..76b1303M. doi:10.1103/PhysRevC.76.021303. S2CID 119443571.
Barber, R. C.; De Laeter, J. R. (2009). "Comment on "Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes"". Phys. Rev. C. 79 (4). 049801. Bibcode:2009PhRvC..79d9801B. doi:10.1103/PhysRevC.79.049801.
Marinov, A.; Rodushkin, I.; Kashiv, Y.; et al. (2009). "Reply to "Comment on 'Existence of long-lived isomeric states in naturally-occurring neutron-deficient Th isotopes'"". Phys. Rev. C. 79 (4). 049802. Bibcode:2009PhRvC..79d9802M. doi:10.1103/PhysRevC.79.049802.
Lachner, J.; Dillmann, I.; Faestermann, T.; et al. (2008). "Search for long-lived isomeric states in neutron-deficient thorium isotopes". Phys. Rev. C. 78 (6). 064313. arXiv:0907.0126. Bibcode:2008PhRvC..78f4313L. doi:10.1103/PhysRevC.78.064313. S2CID 118655846.
Marinov, A.; Rodushkin, I.; Pape, A.; et al. (2009). "Existence of Long-Lived Isotopes of a Superheavy Element in Natural Au" (PDF). International Journal of Modern Physics E. World Scientific. 18 (3): 621–629. arXiv:nucl-ex/0702051. Bibcode:2009IJMPE..18..621M. doi:10.1142/S021830130901280X. S2CID 119103410. Archived from the original (PDF) on 2014-07-14. Retrieved February 12, 2012.
Eliav, Ephraim; Landau, Arie; Ishikawa, Yasuyuki; Kaldor, Uzi (26 March 2002). "Electronic structure of eka-thorium (element 122) compared with thorium". Journal of Physics B: Atomic, Molecular and Optical Physics. 35 (7): 1693–1700. Bibcode:2002JPhB...35.1693E. doi:10.1088/0953-4075/35/7/307. S2CID 250750167.
Chatt, J. (1979). "Recommendations for the Naming of Elements of Atomic Numbers Greater than 100". Pure Appl. Chem. 51 (2): 381–384. doi:10.1351/pac197951020381.
Hoffman, Lee & Pershina 2006, p. 1724.
Greiner, W (2013). "Nuclei: superheavy–superneutronic–strange–and of antimatter" (PDF). Journal of Physics: Conference Series. 413 (1). 012002. Bibcode:2013JPhCS.413a2002G. doi:10.1088/1742-6596/413/1/012002. Retrieved 30 April 2017.
Oganessian, Y. T.; et al. (2002). "Element 118: results from the first 249
Cf
+ 48
Ca
experiment". Communication of the Joint Institute for Nuclear Research. Archived from the original on 22 July 2011.
"Livermore scientists team with Russia to discover element 118" (Press release). Livermore. 3 December 2006. Archived from the original on 17 October 2011. Retrieved 18 January 2008.
Oganessian, Y. T.; Abdullin, F.; Bailey, P. D.; et al. (April 2010). "Synthesis of a New Element with Atomic Number 117" (PDF). Physical Review Letters. 104 (14). 142502. Bibcode:2010PhRvL.104n2502O. doi:10.1103/PhysRevLett.104.142502. PMID 20481935.
Roberto, J. B. (2015). "Actinide Targets for Super-Heavy Element Research" (PDF). cyclotron.tamu.edu. Texas A & M University. Retrieved 30 October 2018.
Hagino, Kouichi; Hofmann, Sigurd; Miyatake, Hiroari; Nakahara, Hiromichi (July 2012). "平成23年度研究業績レビュー（中間レビュー）の実施について" [Implementation of the 2011 Research Achievement Review (Interim Review)] (PDF). www.riken.jp (in Japanese). RIKEN. Archived from the original (PDF) on 2019-03-30. Retrieved 5 May 2017.
Koura, H.; Katakura, J; Tachibana, T; Minato, F (2015). "Chart of the Nuclides". Japan Atomic Energy Agency. Retrieved 30 October 2018.
Barber, R. C.; Karol, P. J.; Nakahara, H.; Vardaci, E.; Vogt, E. W. (2011). "Discovery of the elements with atomic numbers greater than or equal to 113 (IUPAC Technical Report)". Pure and Applied Chemistry. 83 (7): 1. doi:10.1351/PAC-REP-10-05-01.
Ghahramany, N.; Ansari, A. (September 2016). "Synthesis and decay process of superheavy nuclei with Z = 119-122 via hot fusion reactions" (PDF). European Physical Journal A. 52 (287): 287. Bibcode:2016EPJA...52..287G. doi:10.1140/epja/i2016-16287-6. S2CID 125102374.
Pierre de Marcillac; Noël Coron; Gérard Dambier; Jacques Leblanc; Jean-Pierre Moalic (April 2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201. S2CID 4415582.
Considine, Glenn D.; Kulik, Peter H. (2002). Van Nostrand's scientific encyclopedia (9 ed.). Wiley-Interscience. ISBN 978-0-471-33230-5. OCLC 223349096.
Koura, H.; Chiba, S. (2013). "Single-Particle Levels of Spherical Nuclei in the Superheavy and Extremely Superheavy Mass Region". Journal of the Physical Society of Japan. 82 (1). 014201. Bibcode:2013JPSJ...82a4201K. doi:10.7566/JPSJ.82.014201.
Palenzuela, Y. M.; Ruiz, L. F.; Karpov, A.; Greiner, W. (2012). "Systematic Study of Decay Properties of Heaviest Elements" (PDF). Bulletin of the Russian Academy of Sciences: Physics. 76 (11): 1165–1171. Bibcode:2012BRASP..76.1165P. doi:10.3103/s1062873812110172. ISSN 1062-8738. S2CID 120690838.
Kratz, J. V. (5 September 2011). The Impact of Superheavy Elements on the Chemical and Physical Sciences (PDF). 4th International Conference on the Chemistry and Physics of the Transactinide Elements. Retrieved 27 August 2013.
Chowdhury, R. P.; Samanta, C.; Basu, D.N. (2008). "Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130". Atomic Data and Nuclear Data Tables. 94 (6): 781–806. arXiv:0802.4161. Bibcode:2008ADNDT..94..781C. doi:10.1016/j.adt.2008.01.003. S2CID 96718440.
Santhosh, K.P.; Priyanka, B.; Nithya, C. (2016). "Feasibility of observing the α decay chains from isotopes of SHN with Z = 128, Z = 126, Z = 124 and Z = 122". Nuclear Physics A. 955 (November 2016): 156–180. arXiv:1609.05498. Bibcode:2016NuPhA.955..156S. doi:10.1016/j.nuclphysa.2016.06.010. S2CID 119219218.
Poenaru, Dorin N.; Gherghescu, R. A.; Greiner, W. (2012). "Cluster decay of superheavy nuclei". Physical Review C. 85 (3): 034615. Bibcode:2012PhRvC..85c4615P. doi:10.1103/PhysRevC.85.034615. Retrieved 2 May 2017.
Hoffman, Lee & Pershina 2006, p. [page needed].
Umemoto, Koichiro; Saito, Susumu (1996). "Electronic Configurations of Superheavy Elements". Journal of the Physical Society of Japan. 65 (10): 3175–3179. Bibcode:1996JPSJ...65.3175U. doi:10.1143/JPSJ.65.3175. Retrieved 31 January 2021.

Seaborg (c. 2006). "transuranium element (chemical element)". Encyclopædia Britannica. Retrieved 2010-03-16.

Bibliography
Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
Beiser, A. (2003). Concepts of modern physics (6th ed.). McGraw-Hill. ISBN 978-0-07-244848-1. OCLC 48965418.
Hoffman, D. C.; Ghiorso, A.; Seaborg, G. T. (2000). The Transuranium People: The Inside Story. World Scientific. ISBN 978-1-78-326244-1.
Hoffman, D. C.; Lee, D. M.; Pershina, V. (2006). "Transactinides and the future elements". In Morss, L. R.; Edelstein, N. M.; Fuger, J. (eds.). The Chemistry of the Actinide and Transactinide Elements. Vol. 3 (3rd ed.). Dordrecht, The Netherlands: Springer. pp. 1652–1752. ISBN 1-4020-3555-1.
Kragh, H. (2018). From Transuranic to Superheavy Elements: A Story of Dispute and Creation. Springer. ISBN 978-3-319-75813-8.
Zagrebaev, V.; Karpov, A.; Greiner, W. (2013). "Future of superheavy element research: Which nuclei could be synthesized within the next few years?". Journal of Physics: Conference Series. 420 (1). 012001. arXiv:1207.5700. Bibcode:2013JPhCS.420a2001Z. doi:10.1088/1742-6596/420/1/012001. ISSN 1742-6588. S2CID 55434734.

Periodic table

Alkali metals

Alkaline earth metals

Other metals

Other nonmetals

Chemistry Encyclopedia

World

Index

Hellenica World - Scientific Library

Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License