Bohrium

Bohrium is a synthetic chemical element with symbol Bh and atomic number 107. It is named after Danish physicist Niels Bohr. As a synthetic element, it can be created in a laboratory but is not found in nature. It is radioactive: its most stable known isotope, 270Bh, has a half-life of approximately 61 seconds, though the unconfirmed 278Bh may have a longer half-life of about 690 seconds.

In the periodic table of the elements, 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.

Bohrium,  107Bh
Bohrium
Pronunciation/ˈbɔːriəm/ (listen) (BOHR-ee-əm)
Mass number270 (most stable isotope) (unconfirmed: 278)
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

(Uhu)
seaborgiumbohriumhassium
Atomic number (Z)107
Groupgroup 7
Periodperiod 7
Blockd-block
Element category  transition metal
Electron configuration[Rn] 5f14 6d5 7s2[1][2]
Electrons per shell
2, 8, 18, 32, 32, 13, 2
Physical properties
Phase at STPunknown phase (predicted)[3]
Density (near r.t.)37.1 g/cm3 (predicted)[2][4]
Atomic properties
Oxidation states(+3), (+4), (+5), +7[2][4] (parenthesized: prediction)
Ionization energies
  • 1st: 740 kJ/mol
  • 2nd: 1690 kJ/mol
  • 3rd: 2570 kJ/mol
  • (more) (all but first estimated)[2]
Atomic radiusempirical: 128 pm (predicted)[2]
Covalent radius141 pm (estimated)[5]
Other properties
Natural occurrencesynthetic
Crystal structurehexagonal close-packed (hcp)
Hexagonal close-packed crystal structure for bohrium

(predicted)[3]
CAS Number54037-14-8
History
Namingafter Niels Bohr
DiscoveryGesellschaft für Schwerionenforschung (1981)
Main isotopes of bohrium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
267Bh syn 17 s α 263Db
270Bh syn 1 min α 266Db
271Bh syn 1.5 s[6] α 267Db
272Bh syn 11 s α 268Db
274Bh syn 44 s[7] α 270Db
278Bh[8] syn 11.5 min? SF

History

Niels Bohr
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

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.[9] 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.[10]

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 to produce 5 atoms of the isotope bohrium-262:[11]

209
83
Bi
+ 54
24
Cr
262
107
Bh
+
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.[10]

Proposed names

Bohrium hassium meitnerium ceremony
Naming ceremony conducted at the GSI on 7 September 1992 for the namings of elements 107, 108, and 109 as nielsbohrium, hassium, and meitnerium

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 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.[12]

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.[13] In 1994 a committee of IUPAC recommended that element 107 be named bohrium, not nielsbohrium, since there was no precedence for using a scientist's complete name in the naming of an element.[13][14] 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;[13] the names of the respective oxyanions of boron and bohrium remain unchanged despite their homophony.[15]

Isotopes

List of bohrium isotopes
Isotope
Half-life
[16][17]
Decay
mode[16][17]
Discovery
year
Reaction
260Bh 35 ms α 2007 209Bi(52Cr,n)[18]
261Bh 11.8 ms α 1986 209Bi(54Cr,2n)[19]
262Bh 84 ms α 1981 209Bi(54Cr,n)[11]
262mBh 9.6 ms α 1981 209Bi(54Cr,n)[11]
264Bh 0.97 s α 1994 272Rg(—,2α)[20]
265Bh 0.9 s α 2004 243Am(26Mg,4n)[21]
266Bh 0.9 s α 2000 249Bk(22Ne,5n)[22]
267Bh 17 s α 2000 249Bk(22Ne,4n)[22]
270Bh 61 s α 2006 282Nh(—,3α)[23]
271Bh 1.2 s α 2003 287Mc(—,4α)[23]
272Bh 9.8 s α 2005 288Mc(—,4α)[23]
274Bh 40 s α 2009 294Ts(—,5α)[7]
278Bh 11.5 min? SF 1998? 290Fl(ee3α)?

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.[16]

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 61 s and 40 s respectively, and the even heavier unconfirmed isotope 278Bh appearing to have an even longer half-life of about 690 s.

The 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. These eleven isotopes have half-lives ranging from about ten milliseconds for 262mBh to about one minute for 270Bh and 274Bh, extending to about twelve minutes for the unconfirmed 278Bh, one of the longest-lived known superheavy nuclides.[24]

Predicted properties

Chemical

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.[4] 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).[2]

Technetium and rhenium are known to form volatile heptoxides M2O7 (M = 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.[25] 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.[2]

Physical and atomic

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.[3] It should be a very heavy metal with a density of around 37.1 g/cm3, which would be the third-highest of any of the 118 known elements, lower than only meitnerium (37.4 g/cm3) and hassium (41 g/cm3), the two following elements in the periodic table. In comparison, the densest known element that has had its density measured, osmium, has a density of only 22.61 g/cm3. This results from bohrium's high atomic weight, the lanthanide and actinide contractions, and relativistic effects, although production of enough bohrium to measure this quantity would be impractical, and the sample would quickly decay.[2]

The atomic radius of bohrium is expected to be around 128 pm.[2] 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.[2] 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.[2]

Experimental chemistry

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.[26]

In 2000, it was confirmed that although relativistic effects are important, bohrium behaves like a typical group 7 element.[27] 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.[28] 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.[2]

2 Bh + 3 O
2
+ 2 HCl → 2 BhO
3
Cl
+ 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 product, the isotopes 272Bh, 271Bh, and 270Bh can be readily produced as daughters of more easily produced moscovium and nihonium isotopes.[29]

References

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  18. ^ 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.
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External links

Borium

Borium is a product that consists of tungsten carbide granules embedded in a matrix of softer metal. Borium is used in farriery to improve traction for horses. Other applications include ploughshares, saw teeth, cane knives and drill bits. Borium should not be confused with the chemical elements barium, bohrium or boron, the last of which is called borium in a number of languages.

Darmstadtium

Darmstadtium is a synthetic chemical element with symbol Ds and atomic number 110. It is an extremely radioactive synthetic element. The most stable known isotope, darmstadtium-281, has a half-life of approximately 10 seconds. Darmstadtium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near the city of Darmstadt, Germany, after which it was named.

In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and is placed in the group 10 elements, although no chemical experiments have yet been carried out to confirm that it behaves as the heavier homologue to platinum in group 10 as the eighth member of the 6d series of transition metals. Darmstadtium is calculated to have similar properties to its lighter homologues, nickel, palladium, and platinum.

Extended periodic table

An extended periodic table theorizes about chemical elements beyond those currently known in the periodic table and proven up through oganesson, which completes the seventh period (row) in the periodic table at atomic number (Z) 118.

If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out (as with the existing periods) to illustrate periodically recurring trends in the properties of the elements concerned. Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to have an additional so-called g-block, containing at least 18 elements with partially filled g-orbitals in each period.An eight-period table containing this block was suggested by Glenn T. Seaborg in 1969. The first element of the g-block may have atomic number 121, and thus would have the systematic name unbiunium. Despite many searches, no elements in this region have been synthesized or discovered in nature.According to the orbital approximation in quantum mechanical descriptions of atomic structure, the g-block would correspond to elements with partially filled g-orbitals, but spin-orbit coupling effects reduce the validity of the orbital approximation substantially for elements of high atomic number. While Seaborg's version of the extended period had the heavier elements following the pattern set by lighter elements, as it did not take into account relativistic effects, models that take relativistic effects into account do not. Pekka Pyykkö and Burkhard Fricke used computer modeling to calculate the positions of elements up to Z = 172, and found that several were displaced from the Madelung rule. As a result of uncertainty and variability in predictions of chemical and physical properties of elements beyond 120, there is currently no consensus on their placement in the extended periodic table.

Elements in this region are likely to be highly unstable with respect to radioactive decay and undergo alpha decay or spontaneous fission with extremely short half-lives, though element 126 is hypothesized to be within an island of stability that is resistant to fission but not to alpha decay. Other islands of stability beyond the known elements may also be possible, including one theorized around element 164, though the extent of stabilizing effects from closed nuclear shells is uncertain. It is not clear how many elements beyond the expected island of stability are physically possible, whether period 8 is complete, or if there is a period 9. The International Union of Pure and Applied Chemistry (IUPAC) defines an element to exist if its lifetime is longer than 10−14 seconds (0.01 picoseconds, or 10 femtoseconds), which is the time it takes for the nucleus to form an electron cloud.As early as 1940, it was noted that a simplistic interpretation of the relativistic Dirac equation runs into problems with electron orbitals at Z > 1/α ≈ 137, suggesting that neutral atoms cannot exist beyond element 137, and that a periodic table of elements based on electron orbitals therefore breaks down at this point. On the other hand, a more rigorous analysis calculates the analogous limit to be Z ≈ 173 where the 1s subshell dives into the Dirac sea, and that it is instead not neutral atoms that cannot exist beyond element 173, but bare nuclei, thus posing no obstacle to the further extension of the periodic system. Atoms beyond this critical atomic number are called supercritical atoms.

Gottfried Münzenberg

Gottfried Münzenberg (born 17 March 1940 in Nordhausen, Province of Saxony) is a German physicist.

He studied physics at Justus-Liebig-Universität in Giessen and Leopold-Franzens-Universität Innsbruck and completed his studies with a Ph.D. at the University of Giessen, Germany, in 1971. In 1976 he moved to the department of nuclear chemistry at GSI in Darmstadt, Germany, which was headed by Peter Armbruster. He played a leading role in the construction of SHIP, the 'Separator of Heavy Ion Reaction Products'. He was the driving force in the discovery of the cold heavy ion fusion and the discovery of the elements bohrium (Bh Z=107), hassium (Hs Z=108), meitnerium (Mt Z=109), darmstadtium (Ds Z=110), roentgenium (Rg Z=111) and copernicium (Cn Z=112). In 1984 he became head of the new GSI project, the fragment separator, a project which opened new research topics, such as interactions of relativistic heavy ions with matter, production and separation of exotic nuclear beams and structure of exotic nuclei. He directed the Nuclear Structure and Nuclear Chemistry department of the GSI and was professor of physics at the University of Mainz until he retired in March 2005.

Gottfried Münzenberg was born into a family of Protestant ministers (father Pastor Heinz and mother Helene Münzenberg). All his life he is deeply concerned about the philosophical and theological implications of physics.

Among the rewards he received should be mentioned the Röntgen-Prize of the University of Giessen in 1983 and (together with Sigurd Hofmann) the Otto-Hahn-Prize of the city of Frankfurt/Main in 1996.

Group 7 element

Group 7, numbered by IUPAC nomenclature, is a group of elements in the periodic table. They are manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh). All known elements of group 7 are transition metals.

Like other groups, the members of this family show patterns in their electron configurations, especially the outermost shells resulting in trends in chemical behavior.

Inorganic compounds by element

This is a list of common inorganic and organometallic compounds of each element. Compounds are listed alphabetically by their chemical element name rather than by symbol, as in list of inorganic compounds.

Isotopes of bohrium

Bohrium (107Bh) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 262Bh in 1981. There are 11 known isotopes ranging from 260Bh to 274Bh, and 1 isomer, 262mBh. The longest-lived isotope is 270Bh with a half-life of 1 minute, although the unconfirmed 278Bh may have an even longer half-life of about 690 seconds.

Kuşcenneti railway station

Kuşcenneti railway station (Turkish: Kuşcenneti istasyonu) is a railway station in Bandırma, Turkey. The station is located in south Bandırma, near the Bandırma Airport. The station is used mostly as a yard for freight cars serving the nearby Etimaden Bohrium prossesing plant. TCDD Taşımacılık operates two daily intercity trains to İzmir; the northbound 6th of September Express and the southbound 17th of September Express.

List of chemical elements naming controversies

The currently accepted names and symbols of the chemical elements are determined by the International Union of Pure and Applied Chemistry (IUPAC), usually following recommendations by the recognized discoverers of each element. However the names of several elements have been the subject of controversies until IUPAC established an official name. In most cases the controversy was due to a priority dispute as to who first found conclusive evidence for the existence of an element, or as to what evidence was in fact conclusive.

Major actinide

Major actinides is a term used in the nuclear power industry that refers to the plutonium and uranium present in used nuclear fuel, as opposed to the minor actinides neptunium, americium, curium, berkelium, and californium.

Meitnerium

Meitnerium is a synthetic chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds, although the unconfirmed meitnerium-282 may have a longer half-life of 67 seconds. The GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, first created this element in 1982. It is named after Lise Meitner.

In the periodic table, meitnerium is a d-block transactinide element. It is a member of the 7th period and is placed in the group 9 elements, although no chemical experiments have yet been carried out to confirm that it behaves as the heavier homologue to iridium in group 9 as the seventh member of the 6d series of transition metals. Meitnerium is calculated to have similar properties to its lighter homologues, cobalt, rhodium, and iridium.

Minor actinide

The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium (element 93), americium (element 95), curium (element 96), berkelium (element 97), californium (element 98), einsteinium (element 99), and fermium (element 100). The most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.

Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity and heat generation of used nuclear fuel in the medium term (300 to 20,000 years in the future).The plutonium from a power reactor tends to have a greater amount of Pu-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much Pu-241 the presence of americium-241 makes the plutonium less suitable for making a nuclear weapon. The ingrowth of americium in plutonium is one of the methods for identifying the origin of an unknown sample of plutonium and the time since it was last separated chemically from the americium.

Americium is commonly used in industry as both an alpha particle and as a low photon energy gamma radiation source. For instance it is used in many smoke detectors. Americium can be formed by neutron capture of Pu-239 and Pu-240 forming Pu-241 which then beta decays to Am-241. In general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission. Hence if MOX is used in a thermal reactor such as a boiling water reactor (BWR) or pressurized water reactor (PWR) then more americium can be expected in the used fuel than that from a fast neutron reactor.Some of the minor actinides have been found in fallout from bomb tests. See Actinides in the environment for details.

Peter Armbruster

Peter Armbruster (born 25 July 1931 in Dachau, Bavaria) is a physicist at the Gesellschaft für Schwerionenforschung (GSI) facility in Darmstadt, Germany, and is credited with co-discovering elements 107 (bohrium), 108 (hassium), 109 (meitnerium), 110 (darmstadtium), 111 (roentgenium), and 112 (copernicium) with research partner Gottfried Münzenberg.

He studied physics at the Technical University of Stuttgart and Munich, and obtained his Ph.D. in 1961 under Heinz Maier-Leibnitz, Technical University of Munich. His major research fields are fission, interaction of heavy ions in matter and atomic physics with fission product beams at the Research Centre of Jülich (1965 to 1970). He was Senior Scientist at the Gesellschaft für Schwerionenforschung Darmstadt, GSI, from 1971 to 1996. From 1989 to 1992 he was research Director of the European Institut Laue-Langevin (ILL), Grenoble. Since 1996 he has been involved in a project on incineration of nuclear waste by spallation and fission reactions.

He was affiliated as professor to the University of Cologne (1968) and the Darmstadt University of Technology since 1984.

He has received many awards for his work, including the Max-Born Medal awarded by the Institute of Physics London and the Deutsche Physikalische Gesellschaft in 1988, and the Stern-Gerlach Medal awarded by the Deutsche Physikalische Gesellschaft in 1997. The American Chemical Society honoured Peter Armbruster 1997 as one of few non-Americans with the 'Nuclear Chemistry Award'.

Seaborgium

Seaborgium is a synthetic chemical element with symbol Sg and atomic number 106. It is named after the American nuclear chemist Glenn T. Seaborg. As a synthetic element, it can be created in a laboratory but is not found in nature. It is also radioactive; the most stable known isotope, 269Sg, has a half-life of approximately 14 minutes.In the periodic table of the elements, it is a d-block transactinide element. It is a member of the 7th period and belongs to the group 6 elements as the fourth member of the 6d series of transition metals. Chemistry experiments have confirmed that seaborgium behaves as the heavier homologue to tungsten in group 6. The chemical properties of seaborgium are characterized only partly, but they compare well with the chemistry of the other group 6 elements.

In 1974, a few atoms of seaborgium were produced in laboratories in the Soviet Union and in the United States. The priority of the discovery and therefore the naming of the element was disputed between Soviet and American scientists, and it was not until 1997 that International Union of Pure and Applied Chemistry (IUPAC) established seaborgium as the official name for the element. It is one of only two elements named after a living person at the time of naming, the other being oganesson, element 118.

Synthetic element

In chemistry, a synthetic element is a chemical element that does not occur naturally on Earth, and can only be created artificially. So far, 24 synthetic elements have been created (those with atomic numbers 95–118). All are unstable, decaying with half-lives ranging from 15.6 million years to a few hundred microseconds.

Seven other elements were first created artificially and thus considered synthetic, but later discovered to exist naturally (in trace quantities) as well; among them plutonium—first synthesized in 1940—the one best known to laypeople, because of its use in atomic bombs and nuclear reactors.

Transactinide element

In chemistry, transactinide elements (also transactinides, superheavy elements, or super-heavy elements) are the chemical elements with atomic numbers from 104 to 120. Their atomic numbers are immediately greater than those of the actinides, the heaviest of which is lawrencium (atomic number 103).

Glenn T. Seaborg first proposed the actinide concept, which led to the acceptance of the actinide series. He also proposed the transactinide series ranging from element 104 to 121 and the superactinide series approximately spanning elements 122 to 153. The transactinide seaborgium was named in his honor.By definition, transactinide elements are also transuranic elements, i.e. have an atomic number greater than uranium (92).

The transactinide elements all have electrons in the 6d subshell in their ground state. Except for rutherfordium and dubnium, even the longest-lasting isotopes of transactinide elements have extremely short half-lives of minutes or less. The element naming controversy involved the first five or six transactinide elements. These elements thus used systematic names for many years after their discovery had been confirmed. (Usually the systematic names are replaced with permanent names proposed by the discoverers relatively shortly after a discovery has been confirmed.)

Transactinides are radioactive and have only been obtained synthetically in laboratories. None of these elements have ever been collected in a macroscopic sample. Transactinide elements are all named after physicists and chemists or important locations involved in the synthesis of the elements.

IUPAC defines an element to exist if its lifetime is longer than 10−14 seconds, which is the time it takes for the nucleus to form an electron cloud.

Transfermium Wars

The names for the chemical elements 104 to 106 were the subject of a major controversy starting in the 1960s, described by some nuclear chemists as the Transfermium Wars because it concerned the elements following fermium (element 100) on the periodic table.

This controversy arose from disputes between American scientists and Soviet scientists as to which had first isolated these elements. The final resolution of this controversy in 1997 also decided the names of elements 107 to 109.

Transuranium element

The transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92, which is the atomic number of uranium. All of these elements are unstable and decay radioactively into other elements.

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