346 | The History and Use of Our Earth’s Chemical Elements 1975 the nuclear research group in Dubna, Russia, claimed to have discovered the now-named
346 | The History and Use of Our Earth’s Chemical Elements 1975 the nuclear research group in Dubna, Russia, claimed to have discovered the now-named
seaborgium by bombarding isotopes of lead (lead-207 and lead-208) with high-energy ions of chromium-54 to produce seaborgium-259. Three months later, in September 1974, the Lawrence laboratory at Berkeley produced a few atoms of element 106 unnilhexium (element
106 seaborgium). The reaction is as follows: 98 Cf-249 + 8 O-18 → 106 Unh-263 + 4 n-1 (4 0 free neutrons). The Berkeley nuclear reaction that produced Sg-106 was confirmed in 1993, whereas the Dubna reaction was not, resulting in the Berkeley group receiving credit for the discovery of element 106 unnilhexium, which was finally named “seaborgium” in March 1994 by the American Chemical Society, with the name accepted by the IUPAC. (Note: See the entry for element 104, unnilquadium, for more on the seaborgium controversy.)
CommonUses None except for research purposes.
ExamplesofCompounds None now known. However, because seaborgium is a metal, it might be possible for it to
form compounds with some nonmetals such as the halogens. Hazards
The hazards for seaborgium are the same as for any radioactive isotopes, but since only a few short-lived atoms are produced, there is no danger to the public.
BOHRIUM(UNNILSEPTIUM) SYMBOL:Bh(Uns) PERIOD:7 SERIESNAME:Transactinide ATOMICNO:107
ATOMICMASS:˜272amu VALENCE:None OXIDATIONSTATE:Unknown NATURALSTATE:Solid ORIGINOFNAME:NamedafterthescientistNielsBohr. ISOTOPES:Thereareatotalof10isotopesofunnilseptium(bohrium).Notalltheirhalf-lives
areknown.However,theonesthatareknownrangefrom8.0millisecondsto9.8seconds forBh-272,whichisthemoststableisotopeofbohriumandwhichdecaysintodubnium- 268throughalphadecay.Onlyoneisotope,Uns-261,hasadecaymodethatinvolves bothalphadecayandspontaneousfission.Alltheothersdecaybyalphaemission.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=32
s2,p6,d10,f14
6-P=13
s2,p6,d5
7-Q=2
s2
347 PropertiesandCharacteristics
Guide to the Elements |
Unnilseptium, or bohrium, is artificially produced one atom at a time in particle accel- erators. In 1976 Russian scientists at the nuclear research laboratories at Dubna synthesized element 107, which was named unnilseptium by IUPAC. Only a few atoms of element 107 were produced by what is called the “cold fusion” process wherein atoms of one element are slammed into atoms of a different element and their masses combine to form atoms of a new heavier element. Researchers did this by bombarding bismuth-204 with heavy ions of chro- mium-54 in a cyclotron. The reaction follows: Bi-209 + Cr-54 + neutrons = (fuse to form) Uns-262 + an alpha decay chain.
The melting point, boiling point, and density of element 107, as well as some other proper- ties, are not known because of the small number of atoms produced.
History The Russian’s claim of discovery of element 107 in 1976 was disputed by some chem-
ists. In 1981 Peter Armbruster and Gottfried Munzenberg, from their nuclear laboratory in Darmstadt, Germany, claimed they had created element 107 (unnilseptium) in their Separator for Heavy Ion Products (SHIP) as well as some atoms of elements 108 and 109, thus confirming the Russian’s claim for previously producing some atoms of element 107. The German scientists proposed the name nielsbohrium for element 107. In 1992 the IUPAC, along with the American Chemical Society (ACS), changed the name for element 107 to bohrium.
CommonUses None, except for research purposes.
ExamplesofCompounds None are known, but since unnilseptium is a metal, it may be possible for it to chemically
combine with some nonmetals. Hazards
Even though most isotopes of unnilseptium are alpha emitters, there is little radiation hazard because only a few atoms have been produced.
HASSIUM(UNNILOCTIUM) SYMBOL:Hs(Uno) PERIOD:7 SERIESNAME: Transactinide ATOMICNO:108
ATOMICMASS:˜277amu VALENCE:Unknown OXIDATIONSTATE:Unknown NATURALSTATE:Solid
ORIGINOFNAME:NamedforthewordHassias,whichistheLatinnamefortheGerman stateofHesse.
ISOTOPES:Thereareatotalofeightisotopesforunniloctium(hassium)withatomicmass- esrangingfrom263to277andhalf-livesrangingfrom0.8milliseconds(Uno-264)to
348 | The History and Use of Our Earth’s Chemical Elements
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=32
s2,p6,d10,f14
6-P=14
s2,p6,d6
7-Q=2
s2
PropertiesandCharacteristics Most of the chemical and physical properties of unniloctium (hassium) are unknown.
What is known is that its most stable isotope (hassium-108) has the atomic weight (mass) of about 277. Hs-277 has a half-life of about 12 minutes, after which it decays into the isotope seaborgium-273 through either alpha decay or spontaneous fission. Hassium is the last ele- ment located at the bottom of group 8, and like element 107, it is produced by a “cold fusion” process that in hassium’s case is accomplished by “slamming” iron (Fe-58) into particles of the isotope of lead (Pb-209), along with several neutrons, as follows:
82 Pb-209 + 26 Fe-58 + neutrons = 108 Hs-256 +α decay products.
History The physicists Peter Armbruster and Gottfried Munzenberg, using a linear accelerator in
their laboratory in Darmstadt, Germany, produced a few atoms of the element 108 (unniloc- tium) in 1984. Their team also discovered elements 107, 109, 110, and 111. They proposed the name “hassium” for element 108 based on the word hassia, which is the Latin word for the province of Hesse in Germany. In 1992 the IUPAC and the ACS both accepted the name hassium as proposed by the German scientists to replace IUPAC’s temporary name, “unniloc- tium,” even though not much was known about this new synthetic element.
CommonUses Considering that such a small amount of hassium is produced, it has no commercial uses
beyond basic research in nuclear laboratories. ExamplesofCompounds
No common compounds of hassium have been reported. Hazards
Because only a few atom of hassium are produced at a time, radiation hazard is not a problem.
349 MEITNERIUM(UNNILENNIUM)
Guide to the Elements |
SYMBOL:Mt(Une) PERIOD:7 SERIESNAME: Transactinide ATOMICNO:109 ATOMICMASS:˜276amu VALENCE:Unknown OXIDATIONSTATE:Unknown
NATURALSTATE:Solid ORIGINOFNAME:NamedfortheAustrianscientistLiseMeitner. ISOTOPES:Therearefiveisotopesofunnilennium(meitnerium),rangingfromUne-266to
Une-276,andwithhalf-livesrangingfrom1.7millisecondsto0.72seconds.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=32
s2,p6,d10,f14
6-P=15
s2,p6,d7
7-Q=2
s2
PropertiesandCharacteristics Not many chemical and physical properties of Une (or Mt) are known, but it is artificially
produced by the basic process of combining the isotopes of two elements to produce a few atoms of a heavier isotope in linear accelerators. In this case, the creation of a few atoms of element 109 involves a similar nuclear process of fusion as was used for element 108. The reaction follows:
83 Bi-209 + 26 Fe-58 → 109 Une-266 + 0 n-1 (free neutron).
The most stable isotope of unnilennium is meitnerium-276, which has a half-life of about
0.72 seconds. Une-276 decays into element 107 (Uns-272 or bohrium-272). The melting point, boiling point, and density of unnilennium (meitneriumare unknown, as are many of its other chemical and physical properties.