rutherfordium


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rutherfordium

(rŭth'ərfôr`dēəm), artificially produced radioactive chemical element; symbol Rf; at. no. 104; mass number of most stable isotope 265; m.p., b.p., and sp. gr. unknown; valence +4. It is the first transuranium elementtransuranium elements,
in chemistry, radioactive elements with atomic numbers greater than that of uranium (at. no. 92). All the transuranium elements of the actinide series were discovered as synthetic radioactive isotopes at the Univ.
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 beyond the actinide seriesactinide 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.
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, thus being the first of the transactinide elementstransactinide elements
, in chemistry, elements with atomic numbers greater than that of lawrencium (at. no. 103), the last member of the actinide series. See transuranium elements.
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. Situated in Group 4 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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, it has properties similar to those of hafniumhafnium
, metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227°C;; b.p. 4,602°C;; sp. gr. 13.31 at 20°C;; valence +4. Hafnium is a lustrous, ductile, silvery metal with a hexagonal, close-packed crystalline structure.
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 and zirconiumzirconium
, metallic chemical element; symbol Zr; at. no. 40; at. wt. 91.224; m.p. about 1,852°C;; b.p. 4,377°C;; sp. gr. 6.5 at 20°C;; valence +2, +3, or +4.

Zirconium is a very strong, malleable, ductile, lustrous silver-gray metal.
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.

In 1964 a Soviet team led by G. N. Flerov at the Joint Institute for Nuclear Research at Dubna announced the discovery of element 104. They claimed to have isolated an isotope with mass number 260 and a half-lifehalf-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.
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 of 0.3 sec by bombarding plutonium-242 atoms with neon-22 ions. Subsequently, they suggested that element 104 be named kurchatovium (symbol Ku) to honor Igor Kurchatov, a Soviet pioneer in nuclear physics. In 1969, an American research team led by A. Ghiorso at the Lawrence Berkeley National Laboratory announced that, while they had been unable to confirm the Dubna group's results, they had identified at least two isotopes of element 104 different from the one identified by the Soviet scientists. They bombarded californium-249 atoms with carbon-12 and carbon-13 ions to creates isotopes with mass numbers 257 (half-life of 4.8 sec), 259 (half-life of 3 sec), and possibly 258 (half-life of 13 msec). Disputing the Soviet claim of discovery, the Americans suggested the name rutherfordium to honor the British physicist Lord Ernest RutherfordRutherford, Ernest Rutherford, 1st Baron,
1871–1937, British physicist, b. New Zealand. Rutherford left New Zealand in 1895, having earned three degrees from the Univ.
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. An international committee set up to resolve such disputes decided in 1992 that the Berkeley and Dubna laboratories should share credit for the discovery. The syntheses of at least 10 isotopes of rutherfordium, with half-lives ranging from 0.5 msec (Rf-254) to about 13 hr (Rf-265), have been confirmed.

In 1994 a committee of the International Union of Pure and Applied Chemistry (IUPAC), convened to resolve naming disputes for the transactinide elements, recommended that element 104 be named dubniumdubnium
, artificially produced radioactive chemical element; symbol Db; at. no. 105; mass number of most stable isotope 268; m.p., b.p., and sp. gr. unknown; valence +5.
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 in recognition of the work done at the Dubna laboratory. The committee also recommended that element 106, which had been called seaborgiumseaborgium
, artificially produced radioactive chemical element; symbol Sg; at. no. 106; mass number of most stable isotope 271; m.p., b.p., sp. gr., and valence unknown. Situated in Group 6 of the periodic table, it is expected to have properties similar to those of tungsten.
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 by the American team that discovered it, be called rutherfordium. In 1997, however, the name rutherfordium for element 104 was recognized internationally.

See also synthetic elementssynthetic 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.
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.

rutherfordium

[‚rəth·ər′fȯr·dē·əm]
(chemistry)
A chemical element, symbolized Rf, atomic number 104, a synthetic element; the first element beyond the actinide series, and the twelfth transuranium element.

rutherfordium

a transactinide element produced by bombarding californium-249 nuclei with carbon-12 nuclei. Symbol: Rf; atomic number.: 104; atomic wt.: 261