Jump to content

Bohrium

Edit links
This is a good article. Click here for more information.
From Wikipedia, the free encyclopedia

This is the current revision of this page, as edited by IDKhowTo (talk | contribs) at 10:26, 8 October 2024 (Rescuing 3 sources and tagging 0 as dead.) #IABot (v2.0.9.5). The present address (URL) is a permanent link to this version.

(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)
Not to be confused with Borium, barium, or boron.

Bohrium, 107Bh
Bohrium
Pronunciation/ˈbɔːriəm/ ⓘ ​(BOR-ee-əm)
Mass number[270] (data not decisive)[a]
Bohrium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Re
↑
Bh
↓
—
seaborgium ← bohrium → hassium
Atomic number (Z)107
Groupgroup 7
Periodperiod 7
Block  d-block
Electron configuration[Rn] 5f14 6d5 7s2[3][4]
Electrons per shell2, 8, 18, 32, 32, 13, 2
Physical properties
Phase at STPsolid (predicted)[5]
Density (near r.t.)26–27 g/cm3 (predicted)[6][7]
Atomic properties
Oxidation statescommon: (none)
(+3), (+4), (+5), (+7)[4]
Ionization energies
  • 1st: 740 kJ/mol
  • 2nd: 1690 kJ/mol
  • 3rd: 2570 kJ/mol
  • (more) (all but first estimated)[4]
Atomic radiusempirical: 128 pm (predicted)[4]
Covalent radius141 pm (estimated)[8]
Other properties
Natural occurrencesynthetic
Crystal structure ​hexagonal close-packed (hcp)
Hexagonal close-packed crystal structure for bohrium

(predicted)[5]
CAS Number54037-14-8
History
Namingafter Niels Bohr
DiscoveryGesellschaft für Schwerionenforschung (1981)
Isotopes of bohrium
Main isotopes[9] Decay
abun­dance half-life (t1/2) mode pro­duct
267Bh synth 17 s α 263Db
270Bh synth 2.4 min α 266Db
271Bh synth 2.9 s[10] α 267Db
272Bh synth 8.8 s α 268Db
274Bh synth 40 s[11] α 270Db
278Bh synth 11.5 min?[2] SF –
 Category: Bohrium
| references

Bohrium is a synthetic chemical element; it has symbol Bh and atomic number 107. It is named after Danish physicist Niels Bohr. As a synthetic element, it can be created in particle accelerators but is not found in nature. All known isotopes of bohrium are highly radioactive; the most stable known isotope is 270Bh with a half-life of approximately 2.4 minutes, though the unconfirmed 278Bh may have a longer half-life of about 11.5 minutes.

In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and belongs to the group 7 elements as the fifth member of the 6d series of transition metals. Chemistry experiments have confirmed that bohrium behaves as the heavier homologue to rhenium in group 7. The chemical properties of bohrium are characterized only partly, but they compare well with the chemistry of the other group 7 elements.

Introduction

[edit]
This section is an excerpt from Superheavy element § Introduction.[edit]

Synthesis of superheavy nuclei

[edit]
A graphic depiction of a nuclear fusion reaction
A graphic depiction of a nuclear fusion reaction. Two nuclei fuse into one, emitting a neutron. 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[b] atomic nucleus is created in a nuclear reaction that combines two other nuclei of unequal size[c] into one; roughly, the more unequal the two nuclei in terms of mass, the greater the possibility that the two react.[17] 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 only fuse into one 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.[18] The energy applied to the beam nuclei to accelerate them can cause them to reach speeds as high as one-tenth of the speed of light. However, if too much energy is applied, the beam nucleus can fall apart.[18]

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.[18][19] This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.[18] Each pair of a target and a beam is characterized by its cross 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.[d] This fusion may occur as a result of the quantum effect in which nuclei can tunnel 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.[18]

External videos
video icon Visualization of unsuccessful nuclear fusion, based on calculations from the Australian National University[21]

The resulting merger is an excited state[22]—termed a compound nucleus—and thus it is very unstable.[18] To reach a more stable state, the temporary merger may fission without formation of a more stable nucleus.[23] Alternatively, the compound nucleus may eject a few neutrons, which would carry away the excitation energy; if the latter is not sufficient for a neutron expulsion, the merger would produce a gamma ray. This happens in about 10−16 seconds after the initial nuclear collision and results in creation of a more stable nucleus.[23] The definition by the IUPAC/IUPAP Joint Working Party (JWP) 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 electrons and thus display its chemical properties.[24][e]

Decay and detection

[edit]

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.[26] In the separator, the newly produced nucleus is separated from other nuclides (that of the original beam and any other reaction products)[f] 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.[26] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[29] The nucleus is recorded again once its decay is registered, and the location, the energy, and the time of the decay are measured.[26]

Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, its influence on the outermost nucleons (protons and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, and its range is not limited.[30] Total binding 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.[31][32] Superheavy nuclei are thus theoretically predicted[33] and have so far been observed[34] to predominantly decay via decay modes that are caused by such repulsion: alpha decay and spontaneous fission.[g] Almost all alpha emitters have over 210 nucleons,[36] and the lightest nuclide primarily undergoing spontaneous fission has 238.[37] In both decay modes, nuclei are inhibited from decaying by corresponding energy barriers for each mode, but they can be tunneled through.[31][32]

Apparatus for creation of superheavy elements
Scheme of an apparatus for creation of superheavy elements, based on the Dubna Gas-Filled Recoil Separator set up in the Flerov Laboratory of Nuclear Reactions in JINR. The trajectory within the detector and the beam focusing apparatus changes because of a dipole magnet in the former and quadrupole magnets in the latter.[38]

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.[39] Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning.[32] As the atomic number increases, spontaneous fission rapidly becomes more important: spontaneous fission partial half-lives decrease by 23 orders of magnitude from uranium (element 92) to nobelium (element 102),[40] and by 30 orders of magnitude from thorium (element 90) to fermium (element 100).[41] The earlier liquid drop model thus suggested that spontaneous fission would occur nearly instantly due to disappearance of the fission barrier for nuclei with about 280 nucleons.[32][42] The later nuclear shell model suggested that nuclei with about 300 nucleons would form an island of stability in which nuclei will be more resistant to spontaneous fission and will primarily undergo alpha decay with longer half-lives.[32][42] 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.[43] Experiments on lighter superheavy nuclei,[44] as well as those closer to the expected island,[40] have shown greater than previously anticipated stability against spontaneous fission, showing the importance of shell effects on nuclei.[h]

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.[i] (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.)[26] The known nucleus can be recognized by the specific characteristics of decay it undergoes such as decay energy (or more specifically, the kinetic energy of the emitted particle).[j] Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters.[k]

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.[l]

History

[edit]
Element 107 was originally proposed to be named after Niels Bohr, a Danish nuclear physicist, with the name nielsbohrium (Ns). This name was later changed by IUPAC to bohrium (Bh).

Discovery

[edit]

Two groups claimed discovery of the element. Evidence of bohrium was first reported in 1976 by a Soviet research team led by Yuri Oganessian, in which targets of bismuth-209 and lead-208 were bombarded with accelerated nuclei of chromium-54 and manganese-55 respectively.[55] Two activities, one with a half-life of one to two milliseconds, and the other with an approximately five-second half-life, were seen. Since the ratio of the intensities of these two activities was constant throughout the experiment, it was proposed that the first was from the isotope bohrium-261 and that the second was from its daughter dubnium-257. Later, the dubnium isotope was corrected to dubnium-258, which indeed has a five-second half-life (dubnium-257 has a one-second half-life); however, the half-life observed for its parent is much shorter than the half-lives later observed in the definitive discovery of bohrium at Darmstadt in 1981. The IUPAC/IUPAP Transfermium Working Group (TWG) concluded that while dubnium-258 was probably seen in this experiment, the evidence for the production of its parent bohrium-262 was not convincing enough.[56]

In 1981, a German research team led by Peter Armbruster and Gottfried Münzenberg at the GSI Helmholtz Centre for Heavy Ion Research (GSI Helmholtzzentrum für Schwerionenforschung) in Darmstadt bombarded a target of bismuth-209 with accelerated nuclei of chromium-54[57] to produce 5 atoms of the isotope bohrium-262:[58]

209
83Bi
 + 54
24Cr
 → 262
107Bh
 +
n

This discovery was further substantiated by their detailed measurements of the alpha decay chain of the produced bohrium atoms to previously known isotopes of fermium and californium. The IUPAC/IUPAP Transfermium Working Group (TWG) recognised the GSI collaboration as official discoverers in their 1992 report.[56]

Proposed names

[edit]

In September 1992, the German group suggested the name nielsbohrium with symbol Ns to honor the Danish physicist Niels Bohr. The Soviet scientists at the Joint Institute for Nuclear Research in Dubna, Russia had suggested this name be given to element 105 (which was finally called dubnium) and the German team wished to recognise both Bohr and the fact that the Dubna team had been the first to propose the cold fusion reaction, and simultaneously help to solve the controversial problem of the naming of element 105. The Dubna team agreed with the German group's naming proposal for element 107.[59]

There was an element naming controversy as to what the elements from 104 to 106 were to be called; the IUPAC adopted unnilseptium (symbol Uns) as a temporary, systematic element name for this element.[60] In 1994 a committee of IUPAC recommended that element 107 be named bohrium, not nielsbohrium, since there was no precedent for using a scientist's complete name in the naming of an element.[60][61] This was opposed by the discoverers as there was some concern that the name might be confused with boron and in particular the distinguishing of the names of their respective oxyanions, bohrate and borate. The matter was handed to the Danish branch of IUPAC which, despite this, voted in favour of the name bohrium, and thus the name bohrium for element 107 was recognized internationally in 1997;[60] the names of the respective oxyanions of boron and bohrium remain unchanged despite their homophony.[62]

Isotopes

[edit]
Main article: Isotopes of bohrium
List of bohrium isotopes
Isotope Half-life[m] Decay
mode 		Discovery
year 		Discovery
reaction
Value ref
260Bh 41 ms [9] α 2007 209Bi(52Cr,n)[63]
261Bh 12.8 ms [9] α 1986 209Bi(54Cr,2n)[64]
262Bh 84 ms [9] α 1981 209Bi(54Cr,n)[58]
262mBh 9.5 ms [9] α 1981 209Bi(54Cr,n)[58]
264Bh 1.07 s [9] α 1994 272Rg(—,2α)[65]
265Bh 1.19 s [9] α 2004 243Am(26Mg,4n)[66]
266Bh 10.6 s [9] α 2000 249Bk(22Ne,5n)[67]
267Bh 22 s [9] α 2000 249Bk(22Ne,4n)[67]
270Bh 2.4 min [1] α 2006 282Nh(—,3α)[68]
271Bh 2.9 s [1] α 2003 287Mc(—,4α)[68]
272Bh 8.8 s [1] α 2005 288Mc(—,4α)[68]
274Bh 57 s [9] α 2009 294Ts(—,5α)[11]
278Bh 11.5 min? [2] SF 1998? 290Fl(e−,νe3α)?

Bohrium 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. Twelve different isotopes of bohrium have been reported with atomic masses 260–262, 264–267, 270–272, 274, and 278, one of which, bohrium-262, has a known metastable state. All of these but the unconfirmed 278Bh decay only through alpha decay, although some unknown bohrium isotopes are predicted to undergo spontaneous fission.[69]

The lighter isotopes usually have shorter half-lives; half-lives of under 100 ms for 260Bh, 261Bh, 262Bh, and 262mBh were observed. 264Bh, 265Bh, 266Bh, and 271Bh are more stable at around 1 s, and 267Bh and 272Bh have half-lives of about 10 s. The heaviest isotopes are the most stable, with 270Bh and 274Bh having measured half-lives of about 2.4 min and 40 s respectively, and the even heavier unconfirmed isotope 278Bh appearing to have an even longer half-life of about 11.5 minutes.

The most proton-rich isotopes with masses 260, 261, and 262 were directly produced by cold fusion, those with mass 262 and 264 were reported in the decay chains of meitnerium and roentgenium, while the neutron-rich isotopes with masses 265, 266, 267 were created in irradiations of actinide targets. The five most neutron-rich ones with masses 270, 271, 272, 274, and 278 (unconfirmed) appear in the decay chains of 282Nh, 287Mc, 288Mc, 294Ts, and 290Fl respectively. The half-lives of bohrium isotopes range from about ten milliseconds for 262mBh to about one minute for 270Bh and 274Bh, extending to about 11.5 minutes for the unconfirmed 278Bh, which may have one of the longest half-lives among reported superheavy nuclides.[70]

Predicted properties

[edit]

Very few properties of bohrium or its compounds have been measured; this is due to its extremely limited and expensive production[71] and the fact that bohrium (and its parents) decays very quickly. A few singular chemistry-related properties have been measured, but properties of bohrium metal remain unknown and only predictions are available.

Chemical

[edit]

Bohrium is the fifth member of the 6d series of transition metals and the heaviest member of group 7 in the periodic table, below manganese, technetium and rhenium. All the members of the group readily portray their group oxidation state of +7 and the state becomes more stable as the group is descended. Thus bohrium is expected to form a stable +7 state. Technetium also shows a stable +4 state whilst rhenium exhibits stable +4 and +3 states. Bohrium may therefore show these lower states as well.[72] The higher +7 oxidation state is more likely to exist in oxyanions, such as perbohrate, BhO−
4, analogous to the lighter permanganate, pertechnetate, and perrhenate. Nevertheless, bohrium(VII) is likely to be unstable in aqueous solution, and would probably be easily reduced to the more stable bohrium(IV).[4]

The lighter group 7 elements are known to form volatile heptoxides M2O7 (M = Mn, Tc, Re), so bohrium should also form the volatile oxide Bh2O7. The oxide should dissolve in water to form perbohric acid, HBhO4. Rhenium and technetium form a range of oxyhalides from the halogenation of the oxide. The chlorination of the oxide forms the oxychlorides MO3Cl, so BhO3Cl should be formed in this reaction. Fluorination results in MO3F and MO2F3 for the heavier elements in addition to the rhenium compounds ReOF5 and ReF7. Therefore, oxyfluoride formation for bohrium may help to indicate eka-rhenium properties.[73] Since the oxychlorides are asymmetrical, and they should have increasingly large dipole moments going down the group, they should become less volatile in the order TcO3Cl > ReO3Cl > BhO3Cl: this was experimentally confirmed in 2000 by measuring the enthalpies of adsorption of these three compounds. The values are for TcO3Cl and ReO3Cl are −51 kJ/mol and −61 kJ/mol respectively; the experimental value for BhO3Cl is −77.8 kJ/mol, very close to the theoretically expected value of −78.5 kJ/mol.[4]

Physical and atomic

[edit]

Bohrium is expected to be a solid under normal conditions and assume a hexagonal close-packed crystal structure (c/a = 1.62), similar to its lighter congener rhenium.[5] Early predictions by Fricke estimated its density at 37.1 g/cm3,[4] but newer calculations predict a somewhat lower value of 26–27 g/cm3.[6][7]

The atomic radius of bohrium is expected to be around 128 pm.[4] Due to the relativistic stabilization of the 7s orbital and destabilization of the 6d orbital, the Bh+ ion is predicted to have an electron configuration of [Rn] 5f14 6d4 7s2, giving up a 6d electron instead of a 7s electron, which is the opposite of the behavior of its lighter homologues manganese and technetium. Rhenium, on the other hand, follows its heavier congener bohrium in giving up a 5d electron before a 6s electron, as relativistic effects have become significant by the sixth period, where they cause among other things the yellow color of gold and the low melting point of mercury. The Bh2+ ion is expected to have an electron configuration of [Rn] 5f14 6d3 7s2; in contrast, the Re2+ ion is expected to have a [Xe] 4f14 5d5 configuration, this time analogous to manganese and technetium.[4] The ionic radius of hexacoordinate heptavalent bohrium is expected to be 58 pm (heptavalent manganese, technetium, and rhenium having values of 46, 57, and 53 pm respectively). Pentavalent bohrium should have a larger ionic radius of 83 pm.[4]

Experimental chemistry

[edit]

In 1995, the first report on attempted isolation of the element was unsuccessful, prompting new theoretical studies to investigate how best to investigate bohrium (using its lighter homologs technetium and rhenium for comparison) and removing unwanted contaminating elements such as the trivalent actinides, the group 5 elements, and polonium.[74]

In 2000, it was confirmed that although relativistic effects are important, bohrium behaves like a typical group 7 element.[75] A team at the Paul Scherrer Institute (PSI) conducted a chemistry reaction using six atoms of 267Bh produced in the reaction between 249Bk and 22Ne ions. The resulting atoms were thermalised and reacted with a HCl/O2 mixture to form a volatile oxychloride. The reaction also produced isotopes of its lighter homologues, technetium (as 108Tc) and rhenium (as 169Re). The isothermal adsorption curves were measured and gave strong evidence for the formation of a volatile oxychloride with properties similar to that of rhenium oxychloride. This placed bohrium as a typical member of group 7.[76] The adsorption enthalpies of the oxychlorides of technetium, rhenium, and bohrium were measured in this experiment, agreeing very well with the theoretical predictions and implying a sequence of decreasing oxychloride volatility down group 7 of TcO3Cl > ReO3Cl > BhO3Cl.[4]

2 Bh + 3 O
2 + 2 HCl → 2 BhO
3Cl + H
2

The longer-lived heavy isotopes of bohrium, produced as the daughters of heavier elements, offer advantages for future radiochemical experiments. Although the heavy isotope 274Bh requires a rare and highly radioactive berkelium target for its production, the isotopes 272Bh, 271Bh, and 270Bh can be readily produced as daughters of more easily produced moscovium and nihonium isotopes.[77]

Notes

[edit]
  1. ^ The most stable isotope of bohrium cannot be determined based on existing data due to uncertainty that arises from the low number of measurements. The half-life of 270Bh corresponding to two standard deviations is, based on existing data, 2.4+8.8
    −1.8     minutes[1], whereas that of 274Bh is 44+68
    −26     seconds; these measurements have overlapping confidence intervals. It is also possible that the unconfirmed 278Bh is more stable than both of these, with its half-life being 11.5 minutes.[2]
  2. ^ 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[12] or 112;[13] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypothetical superactinide series).[14] 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.
  3. ^ In 2009, a team at the 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.[15] 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.[16]
  4. ^ The amount of energy applied to the beam particle to accelerate it can also influence the value of cross section. For example, in the 28
    14    Si
     + 1
    0    n
     → 28
    13    Al
     + 1
    1    p
     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.[20]
  5. ^ This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[25]
  6. ^ 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.[27] 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.[28]
  7. ^ Not all decay modes are caused by electrostatic repulsion. For example, beta decay is caused by the weak interaction.[35]
  8. ^ 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.[40]
  9. ^ 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.[45] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[46] 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).[47]
  10. ^ If the decay occurred in a vacuum, then since total momentum of an isolated system before and after the decay must 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).[36] 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.
  11. ^ Spontaneous fission was discovered by Soviet physicist Georgy Flerov,[48] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[49] 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.[25] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[48]
  12. ^ For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics in Stockholm, Stockholm County, Sweden.[50] 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.[51] 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.[51] JINR insisted that they were the first to create the element and suggested a name of their own for the new element, joliotium;[52] the Soviet name was also not accepted (JINR later referred to the naming of the element 102 as "hasty").[53] This name was proposed to IUPAC in a written response to their ruling on priority of discovery claims of elements, signed 29 September 1992.[53] The name "nobelium" remained unchanged on account of its widespread usage.[54]
  13. ^ Different sources give different values for half-lives; the most recently published values are listed.

References

[edit]
  1. ^ a b c d Oganessian, Yu. Ts.; Utyonkov, V. K.; Kovrizhnykh, N. D.; et al. (2022). "New isotope 286Mc produced in the 243Am+48Ca reaction". Physical Review C. 106 (64306): 064306. Bibcode:2022PhRvC.106f4306O. doi:10.1103/PhysRevC.106.064306. S2CID 254435744.
  2. ^ a b c Hofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; Burkhard, H. G.; Dahl, L.; Eberhardt, K.; Grzywacz, R.; Hamilton, J. H.; Henderson, R. A.; Kenneally, J. M.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Miernik, K.; Miller, D.; Moody, K. J.; Morita, K.; Nishio, K.; Popeko, A. G.; Roberto, J. B.; Runke, J.; Rykaczewski, K. P.; Saro, S.; Scheidenberger, C.; Schött, H. J.; Shaughnessy, D. A.; Stoyer, M. A.; Thörle-Popiesch, P.; Tinschert, K.; Trautmann, N.; Uusitalo, J.; Yeremin, A. V. (2016). "Review of even element super-heavy nuclei and search for element 120". The European Physics Journal A. 2016 (52). Bibcode:2016EPJA...52..180H. doi:10.1140/epja/i2016-16180-4.
  3. ^ Johnson, E.; Fricke, B.; Jacob, T.; Dong, C. Z.; Fritzsche, S.; Pershina, V. (2002). "Ionization potentials and radii of neutral and ionized species of elements 107 (bohrium) and 108 (hassium) from extended multiconfiguration Dirac–Fock calculations". The Journal of Chemical Physics. 116 (5): 1862–1868. Bibcode:2002JChPh.116.1862J. doi:10.1063/1.1430256.
  4. ^ a b c d e f g h i j k Hoffman, 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. ISBN 978-1-4020-3555-5.
  5. ^ a b c Östlin, A.; Vitos, L. (2011). "First-principles calculation of the structural stability of 6d transition metals". Physical Review B. 84 (11). Bibcode:2011PhRvB..84k3104O. doi:10.1103/PhysRevB.84.113104.
  6. ^ a b Gyanchandani, Jyoti; Sikka, S. K. (10 May 2011). "Physical properties of the 6 d -series elements from density functional theory: Close similarity to lighter transition metals". Physical Review B. 83 (17): 172101. doi:10.1103/PhysRevB.83.172101.
  7. ^ a b Kratz; Lieser (2013). Nuclear and Radiochemistry: Fundamentals and Applications (3rd ed.). p. 631.
  8. ^ Chemical Data. Bohrium - Bh, Royal Chemical Society
  9. ^ a b c d e f g h i j Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  10. ^ FUSHE (2012). "Synthesis of SH-nuclei". Retrieved August 12, 2016.
  11. ^ a b Oganessian, Yuri Ts.; Abdullin, F. Sh.; Bailey, P. D.; et al. (2010-04-09). "Synthesis of a New Element with Atomic Number Z=117". Physical Review Letters. 104 (142502). American Physical Society. Bibcode:2010PhRvL.104n2502O. doi:10.1103/PhysRevLett.104.142502. PMID 20481935. (gives life-time of 1.3 min based on a single event; conversion to half-life is done by multiplying with ln(2).)
  12. ^ Krämer, K. (2016). "Explainer: superheavy elements". Chemistry World. Retrieved 2020-03-15.
  13. ^ "Discovery of Elements 113 and 115". Lawrence Livermore National Laboratory. Archived from the original on 2015-09-11. Retrieved 2020-03-15.
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ Subramanian, S. (28 August 2019). "Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist". Bloomberg Businessweek. Retrieved 2020-01-18.
  18. ^ a b c d e f Ivanov, D. (2019). "Сверхтяжелые шаги в неизвестное" [Superheavy steps into the unknown]. nplus1.ru (in Russian). Retrieved 2020-02-02.
  19. ^ Hinde, D. (2017). "Something new and superheavy at the periodic table". The Conversation. Retrieved 2020-01-30.
  20. ^ Kern, B. D.; Thompson, W. E.; Ferguson, J. M. (1959). "Cross sections for some (n, p) and (n, α) reactions". Nuclear Physics. 10: 226–234. Bibcode:1959NucPh..10..226K. doi:10.1016/0029-5582(59)90211-1.
  21. ^ 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. hdl:1885/148847. ISSN 2100-014X.
  22. ^ "Nuclear Reactions" (PDF). pp. 7–8. Retrieved 2020-01-27. Published as Loveland, W. D.; Morrissey, D. J.; Seaborg, G. T. (2005). "Nuclear Reactions". Modern Nuclear Chemistry. John Wiley & Sons, Inc. pp. 249–297. doi:10.1002/0471768626.ch10. ISBN 978-0-471-76862-3.
  23. ^ a b Krása, A. (2010). "Neutron Sources for ADS". Faculty of Nuclear Sciences and Physical Engineering. Czech Technical University in Prague: 4–8. S2CID 28796927.
  24. ^ 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.
  25. ^ a b 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.
  26. ^ a b c d Chemistry World (2016). "How to Make Superheavy Elements and Finish the Periodic Table [Video]". Scientific American. Retrieved 2020-01-27.
  27. ^ Hoffman, Ghiorso & Seaborg 2000, p. 334.
  28. ^ Hoffman, Ghiorso & Seaborg 2000, p. 335.
  29. ^ Zagrebaev, Karpov & Greiner 2013, p. 3.
  30. ^ Beiser 2003, p. 432.
  31. ^ a b Pauli, N. (2019). "Alpha decay" (PDF). Introductory Nuclear, Atomic and Molecular Physics (Nuclear Physics Part). Université libre de Bruxelles. Retrieved 2020-02-16.
  32. ^ a b c d e Pauli, N. (2019). "Nuclear fission" (PDF). Introductory Nuclear, Atomic and Molecular Physics (Nuclear Physics Part). Université libre de Bruxelles. Retrieved 2020-02-16.
  33. ^ 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.
  34. ^ Audi et al. 2017, pp. 030001-129–030001-138.
  35. ^ Beiser 2003, p. 439.
  36. ^ a b Beiser 2003, p. 433.
  37. ^ Audi et al. 2017, p. 030001-125.
  38. ^ Aksenov, N. V.; Steinegger, P.; Abdullin, F. Sh.; et al. (2017). "On the volatility of nihonium (Nh, Z = 113)". The European Physical Journal A. 53 (7): 158. Bibcode:2017EPJA...53..158A. doi:10.1140/epja/i2017-12348-8. ISSN 1434-6001. S2CID 125849923.
  39. ^ Beiser 2003, p. 432–433.
  40. ^ a b c Oganessian, Yu. (2012). "Nuclei in the "Island of Stability" of Superheavy Elements". Journal of Physics: Conference Series. 337 (1): 012005-1–012005-6. Bibcode:2012JPhCS.337a2005O. doi:10.1088/1742-6596/337/1/012005. ISSN 1742-6596.
  41. ^ Moller, P.; Nix, J. R. (1994). Fission properties of the heaviest elements (PDF). Dai 2 Kai Hadoron Tataikei no Simulation Symposium, Tokai-mura, Ibaraki, Japan. University of North Texas. Retrieved 2020-02-16.
  42. ^ a b Oganessian, Yu. Ts. (2004). "Superheavy elements". Physics World. 17 (7): 25–29. doi:10.1088/2058-7058/17/7/31. Retrieved 2020-02-16.
  43. ^ Schädel, M. (2015). "Chemistry of the superheavy elements". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 373 (2037): 20140191. Bibcode:2015RSPTA.37340191S. doi:10.1098/rsta.2014.0191. ISSN 1364-503X. PMID 25666065.
  44. ^ Hulet, E. K. (1989). Biomodal spontaneous fission. 50th Anniversary of Nuclear Fission, Leningrad, USSR. Bibcode:1989nufi.rept...16H.
  45. ^ 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.
  46. ^ Grant, A. (2018). "Weighing the heaviest elements". Physics Today. doi:10.1063/PT.6.1.20181113a. S2CID 239775403.
  47. ^ Howes, L. (2019). "Exploring the superheavy elements at the end of the periodic table". Chemical & Engineering News. Retrieved 2020-01-27.
  48. ^ a b Robinson, A. E. (2019). "The Transfermium Wars: Scientific Brawling and Name-Calling during the Cold War". Distillations. Retrieved 2020-02-22.
  49. ^ "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.
  50. ^ "Nobelium - Element information, properties and uses | Periodic Table". Royal Society of Chemistry. Retrieved 2020-03-01.
  51. ^ a b Kragh 2018, pp. 38–39.
  52. ^ Kragh 2018, p. 40.
  53. ^ a b 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.
  54. ^ 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.
  55. ^ Yu; Demin, A.G.; Danilov, N.A.; Flerov, G.N.; Ivanov, M.P.; Iljinov, A.S.; Kolesnikov, N.N.; Markov, B.N.; Plotko, V.M.; Tretyakova, S.P. (1976). "On spontaneous fission of neutron-deficient isotopes of elements". Nuclear Physics A. 273: 505–522. doi:10.1016/0375-9474(76)90607-2.
  56. ^ a b Barber, R. C.; Greenwood, N. N.; Hrynkiewicz, A. Z.; Jeannin, Y. P.; Lefort, M.; Sakai, M.; Ulehla, I.; Wapstra, A. P.; Wilkinson, D. H. (1993). "Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements". Pure and Applied Chemistry. 65 (8): 1757. doi:10.1351/pac199365081757. S2CID 195819585.
  57. ^ "Bohrium (Bh) Properties, Applications & Research | AMERICAN ELEMENTS ®". American Elements: The Materials Science Company. Archived from the original on 2024-06-19. Retrieved 2024-09-27.
  58. ^ a b c Münzenberg, G.; Hofmann, S.; Heßberger, F. P.; Reisdorf, W.; Schmidt, K. H.; Schneider, J. H. R.; Armbruster, P.; Sahm, C. C.; Thuma, B. (1981). "Identification of element 107 by α correlation chains". Zeitschrift für Physik A. 300 (1): 107–8. Bibcode:1981ZPhyA.300..107M. doi:10.1007/BF01412623. S2CID 118312056. Retrieved 24 December 2016.
  59. ^ Ghiorso, A.; Seaborg, G. T.; Organessian, Yu. Ts.; Zvara, I.; Armbruster, P.; Hessberger, F. P.; Hofmann, S.; Leino, M.; Munzenberg, G.; Reisdorf, W.; Schmidt, K.-H. (1993). "Responses on 'Discovery of the transfermium elements' by Lawrence Berkeley Laboratory, California; Joint Institute for Nuclear Research, Dubna; and Gesellschaft fur Schwerionenforschung, Darmstadt followed by reply to responses by the Transfermium Working Group". Pure and Applied Chemistry. 65 (8): 1815–1824. doi:10.1351/pac199365081815.
  60. ^ a b c 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. Archived (PDF) from the original on 2021-10-11. Retrieved 2023-07-11.
  61. ^ "Names and symbols of transfermium elements (IUPAC Recommendations 1994)". Pure and Applied Chemistry. 66 (12): 2419–2421. 1994. doi:10.1351/pac199466122419.
  62. ^ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. pp. 337–9. Electronic version.
  63. ^ Nelson, S.; Gregorich, K.; Dragojević, I.; Garcia, M.; Gates, J.; Sudowe, R.; Nitsche, H. (2008). "Lightest Isotope of Bh Produced via the Bi209(Cr52,n)Bh260 Reaction" (PDF). Physical Review Letters. 100 (2): 022501. Bibcode:2008PhRvL.100b2501N. doi:10.1103/PhysRevLett.100.022501. PMID 18232860. S2CID 1242390. Archived (PDF) from the original on 2022-10-09.
  64. ^ Münzenberg, G.; Armbruster, P.; Hofmann, S.; Heßberger, F. P.; Folger, H.; Keller, J. G.; Ninov, V.; Poppensieker, K.; et al. (1989). "Element 107". Zeitschrift für Physik A. 333 (2): 163. Bibcode:1989ZPhyA.333..163M. doi:10.1007/BF01565147. S2CID 186231905.
  65. ^ Hofmann, S.; Ninov, V.; Heßberger, F. P.; Armbruster, P.; Folger, H.; Münzenberg, G.; Schött, H. J.; Popeko, A. G.; Yeremin, A. V.; Andreyev, A. N.; Saro, S.; Janik, R.; Leino, M. (1995). "The new element 111". Zeitschrift für Physik A. 350 (4): 281. Bibcode:1995ZPhyA.350..281H. doi:10.1007/BF01291182. S2CID 18804192.
  66. ^ Gan, Z.G.; Guo, J. S.; Wu, X. L.; Qin, Z.; Fan, H. M.; Lei, X. G.; Liu, H. Y.; Guo, B.; et al. (2004). "New isotope 265Bh". The European Physical Journal A. 20 (3): 385. Bibcode:2004EPJA...20..385G. doi:10.1140/epja/i2004-10020-2. S2CID 120622108.
  67. ^ a b Wilk, P. A.; Gregorich, K. E.; Turler, A.; Laue, C. A.; Eichler, R.; Ninov V, V.; Adams, J. L.; Kirbach, U. W.; et al. (2000). "Evidence for New Isotopes of Element 107: 266Bh and 267Bh". Physical Review Letters. 85 (13): 2697–700. Bibcode:2000PhRvL..85.2697W. doi:10.1103/PhysRevLett.85.2697. PMID 10991211. Archived from the original on 2019-12-26. Retrieved 2018-11-04.
  68. ^ a b c Oganessian, Yu. Ts. (2007). "Heaviest Nuclei Produced in 48Ca-induced Reactions (Synthesis and Decay Properties)". In Penionzhkevich, Yu. E.; Cherepanov, E. A. (eds.). AIP Conference Proceedings: International Symposium on Exotic Nuclei. Vol. 912. p. 235. doi:10.1063/1.2746600. ISBN 978-0-7354-0420-5.
  69. ^ Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Archived from the original on 2019-04-02. Retrieved 2008-06-06.
  70. ^ Münzenberg, G.; Gupta, M. (2011). "Production and Identification of Transactinide Elements". In Vértes, Attila; Nagy, Sándor; Klencsár, Zoltán; Lovas, Rezső G.; Rösch, Frank (eds.). Handbook of Nuclear Chemistry: Production and Identification of Transactinide Elements. p. 877. doi:10.1007/978-1-4419-0720-2_19. ISBN 978-1-4419-0719-6.
  71. ^ 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.
  72. ^ Fricke, Burkhard (1975). "Superheavy elements: a prediction of their chemical and physical properties". Recent Impact of Physics on Inorganic Chemistry. Structure and Bonding. 21: 89–144. doi:10.1007/BFb0116498. ISBN 978-3-540-07109-9. Retrieved 4 October 2013.
  73. ^ Hans Georg Nadler "Rhenium and Rhenium Compounds" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2000. doi:10.1002/14356007.a23_199
  74. ^ Malmbeck, R.; Skarnemark, G.; Alstad, J.; Fure, K.; Johansson, M.; Omtvedt, J. P. (2000). "Chemical Separation Procedure Proposed for Studies of Bohrium". Journal of Radioanalytical and Nuclear Chemistry. 246 (2): 349. Bibcode:2000JRNC..246..349M. doi:10.1023/A:1006791027906. S2CID 93640208.
  75. ^ Gäggeler, H. W.; Eichler, R.; Brüchle, W.; Dressler, R.; Düllmann, Ch. E.; Eichler, B.; Gregorich, K. E.; Hoffman, D. C.; et al. (2000). "Chemical characterization of bohrium (element 107)". Nature. 407 (6800): 63–5. Bibcode:2000Natur.407...63E. doi:10.1038/35024044. PMID 10993071. S2CID 4398253.
  76. ^ Eichler, R.; et al. "Gas chemical investigation of bohrium (Bh, element 107)" (PDF). GSI Annual Report 2000. Archived from the original (PDF) on 2012-02-19. Retrieved 2008-02-29.
  77. ^ Moody, Ken (2013-11-30). "Synthesis of Superheavy Elements". In Schädel, Matthias; Shaughnessy, Dawn (eds.). The Chemistry of Superheavy Elements (2nd ed.). Springer Science & Business Media. pp. 24–8. ISBN 9783642374661.

Bibliography

[edit]
[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=Bohrium&oldid=1250076452"