nobelium


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nobelium

(nōbē`lēəm), artificially produced radioactive chemical element; symbol No; at. no. 102; mass no. of most stable isotope 259; m.p. 827°C;; b.p. and density unknown; valence +2, +3. It is a metal of 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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 in Group 3 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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. Nobelium was the 10th 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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 to be discovered. It was first produced and detected in Apr., 1958, by Albert Ghiorso, Torbjørn Sikkeland, John R. Walton, and Glenn T. SeaborgSeaborg, Glenn Theodore
, 1912–99, American chemist, b. Ishpeming, Mich., grad. Univ. of California at Los Angeles, 1934, Ph.D. Univ. of California at Berkeley, 1937.
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 at the Univ. of California at Berkeley; they used a heavy-ion linear accelerator to bombard a mixture of curium-244 and curium-246 with carbon-12 ions, producing nobelium-254 (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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 55 sec). The name of the element was originally suggested by scientists at the Nobel Institute of Physics, who in 1957 reported synthesis of an isotope of the element; although the name was adopted, it was later shown that the element could not have the properties they reported. Thirteen isotopes, all of which are radioactive, are known; the most stable, nobelium-259, has a 58-min half-life.

Nobelium

 

No (element 102), an artificially produced radioactive chemical element of the actinide family, with atomic number 102.

The preparation of atoms of element 102 was first announced in 1957 by an international group of scientists working in Stockholm, Sweden, that also proposed that the element be named in honor of A. Nobel, the founder of a fund for international prizes (Nobel Prizes). However, subsequent experiments conducted at Berkeley (USA) and the Joint Institute for Atomic Studies (Dubna, USSR) showed that the conclusion of the Stockholm group was erroneous.

The first reliable information on isotopes of element 102 with mass numbers 251–256 was obtained during the period from 1963 to 1967 by a group of Soviet physicists at Dubna, headed by G. N. Flerov. For the synthesis of these isotopes the Soviet group irradiated nuclei of isotopes of uranium, plutonium, and americium with accelerated ions of neon, oxygen, and nitrogen. The results of the Dubna group have been fully confirmed. The Soviet scientists have proposed naming element 102 joliotium (symbol Jl) in honor of Jean Frédéric Joliot-Curie. As yet there is no commonly accepted name for element 102.

As of 1974, isotopes of nobelium with mass numbers from 251 to 259 had been obtained in microscopic quantities. The most long-lived isotope, 259102 (half-life, about 1.5 hr), was synthesized in 1970 at Oak Ridge (USA). The first chemical identification of element 102 was carried out by a group of Flerov’s colleagues using a technique developed for studying kurcha-tovium. The volatility of the chloride of element 102 is similar to that of the chlorides of fermium and californium. The most stable oxidation state of nobelium in solution is + 2; it may pass into an oxidation state of + 3 under the action of strong oxidizing agents.

nobelium

[nō′bel·ē·əm]
(chemistry)
A chemical element, symbol No, atomic number 102; a synthetic element, in the actinium series; isotopes with mass numbers 250-260 and 262 have been produced in the laboratory, with mass number 259 having the longest known half-life, 58 minutes.

nobelium

a transuranic element produced artificially from curium. Symbol: No; atomic no.: 102; half-life of most stable isotope, 255No: 180 seconds (approx.); valency: 2 or 3