transuranium elements definition of transuranium elements in the Free Online Encyclopedia.

transuranium elements, in chemistry, radioactive elements with atomic numbers greater than that of uranium uranium (y
..... Click the link for more information. (at. no. 92). All the transuranium elements of the actinide series actinide series, a series of radioactive metallic elements in Group 3 of the periodic table . Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series.
..... Click the link for more information. were discovered as synthetic radioactive isotopes at the Univ. of California at Berkeley or at Argonne National Laboratory; in order of increasing atomic number they are neptunium neptunium (nĕpt
..... Click the link for more information. , plutonium plutonium (pl
..... Click the link for more information. , americium americium (ămərĭ`shēəm), artificially produced radioactive chemical element; symbol Am; at. no. 95; mass no.
..... Click the link for more information. , curium curium (ky
..... Click the link for more information. , berkelium berkelium (bûr`klēəm) [from Berkeley ], artificially produced radioactive chemical element; symbol Bk; at. no. 97; mass no.
..... Click the link for more information. , californium californium (kăl`ĭfôr'nēəm)
..... Click the link for more information. , einsteinium einsteinium (īn`stī'nēəm, īnstī`–)
..... Click the link for more information. , fermium fermium (fûr`mēəm) [for Enrico Fermi ], artificially produced radioactive chemical element; symbol Fm; at. no. 100; mass no.
..... Click the link for more information. , mendelevium mendelevium (mĕndəlāv`ēəm), artificially produced radioactive chemical element; symbol Md; at. no. 101; mass no.
..... Click the link for more information. , nobelium nobelium (nōbē`lēəm), artificially produced radioactive chemical element; symbol No; at. no. 102; mass no.
..... Click the link for more information. , and lawrencium lawrencium, artificially produced radioactive chemical element; symbol Lr; at. no. 103; mass number of most stable isotope 262; m.p. about 1,627°C;; b.p. and sp. gr. unknown; valence +3.
..... Click the link for more information. . Of these only neptunium and plutonium occur in nature; they are produced in minute amounts in the radioactive decay of uranium.

Much of the study of the transuranium elements has taken place at the Lawrence Berkeley National Laboratory (at Berkeley, Calif.) and at the Joint Institute for Nuclear Research in Dubna, Russia; workers at both locations share credit for the independent discovery of rutherfordium rutherfordium (rŭth'ərfôr`dēəm), artificially produced radioactive chemical element; symbol Rf; at. no.
..... Click the link for more information. , dubnium dubnium (d
..... Click the link for more information. , and seaborgium seaborgium (sēbôr`gēəm), artificially produced radioactive chemical element; symbol Sg; at. no.
..... Click the link for more information. (at. no. 104, 105, and 106, respectively), which are the first three transactinide elements transactinide elements (trăns'ăk`tənīd'), in chemistry, elements with atomic numbers greater than that of lawrencium (at.
..... Click the link for more information. . A German team at the Institute for Heavy Ion Research at Darmstadt discovered bohrium bohrium (bôr`ēəm), artificially produced radioactive chemical element; symbol Bh; at. no.
..... Click the link for more information. , hassium hassium (hăs`ēəm, häs`–), artificially produced radioactive chemical element; symbol Hs; at. no.
..... Click the link for more information. , meitnerium meitnerium (mītnĭr`ēəm), artificially produced radioactive chemical element; symbol Mt; at. no.
..... Click the link for more information. , darmstadtium darmstadtium, artificially produced radioactive chemical element; symbol Ds; at. no. 110; mass number of most stable isotope 271; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. , roentgenium roentgenium, artificially produced radioactive chemical element; symbol Rg; at. no. 111; mass number of most stable isotope 272; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. , and ununbium ununbium (y
..... Click the link for more information. (at. no. 107 through 112). The Dubna laboratory, with assistance from Berkeley, claims to have synthesized ununquadium ununquadium (y
..... Click the link for more information. (at. no. 114), and working jointly with the Lawrence Livermore National Laboratory (at Livermore, Calif.) claims to have produced ununtrium ununtrium, artificially produced radioactive chemical element; symbol Uut; at. no. 113; mass number of most stable isotope 284; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. (at. no. 113) and ununpentium ununpentium, artificially produced radioactive chemical element; symbol Uup; at. no. 115; mass number of most stable isotope 288; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. (at. no. 115). The Berkeley team claimed to have produced ununhexium ununhexium (y
..... Click the link for more information. (at. no. 116) and ununoctium ununoctium (y
..... Click the link for more information. (at. no. 118), but later retracted the claim for ununoctium after other laboratories failed to reproduce Berkeley's results and a reanalysis of their data did not show the production of the element. Other research teams have since synthesized ununhexium directly.

Up to and including fermium (at. no. 100), the transuranium elements are produced by the capture of neutrons; the transfermium elements are synthesized by the bombardment of transuranium targets with light particles or, more recently, by projecting medium-weight elements at targets of other medium-weight elements (see also synthetic elements synthetic elements, in chemistry, radioactive elements that were not discovered occurring in nature but as artificially produced isotopes. They are technetium (at. no. 43), which was the first element to be synthesized, promethium (at. no. 61), astatine (at. no.
..... Click the link for more information. ).

Isotopes of the transuranium elements are radioactive because their large nuclei are unstable, and the transactinide, or superheavy, elements in particular have very short half-lives half-life, measure of the average lifetime of a radioactive substance (see radioactivity ) or an unstable subatomic particle. One half-life is the time required for one half of any given quantity of the substance to decay.
..... Click the link for more information. . However, on the basis of theories of nuclear structure, physicists have predicted that certain transactinide elements may have relatively stable isotopes. For example, an isotope of element 114 with mass number 298 (comprising 114 protons and 184 neutrons) should be very stable and resemble lead in its chemical properties. However, the three isotopes of element 114 that are claimed to have been synthesized have fewer than the requisite 184 neutrons.

Bibliography

See G. T. Seaborg and W. D. Loveland, The Elements beyond Uranium (1990); L. R. Morss and J. Fuger, ed., Transuranium Elements (1992); G. T. Seaborg and A. Ghiorso, The Transuranium People (1999).

transuranium elements [¦tranz·yu̇′rā·nē·əm ′el·ə·məns]

(chemistry)

transuranic elements