lawrencium

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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. Lawrencium is the last member 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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 of elements found 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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. Lawrencium was the 11th 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 prepared in 1961 (after three years of preliminary work) by Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, and Robert M. Latimer at the Univ. of California at Berkeley; a sample of californium isotopes was bombarded with a beam of boron nuclei from the heavy-ion linear accelerator. The resulting isotope, lawrencium-258, had 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 4.2 sec. The element was named for Ernest O. LawrenceLawrence, Ernest Orlando,
1901–58, American physicist, b. Canton, S. Dak., grad. Univ. of South Dakota, 1922, Ph.D. Yale, 1925. Affiliated with the Univ. of California from 1928 onward, he became a professor in 1930 and director of its radiation laboratory in 1936.
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, the inventor of the cyclotron. The symbol Lw was used at first, but it was changed to Lr in 1963. Ten isotopes, all of which are radioactive, are known; the most stable, lawrencium-262, has a half-life of 3.6 hours.

lawrencium

[′lȯ′ren·sē·əm]
(chemistry)
A chemical element, symbol Lr, atomic number 103; isotopes with mass numbers 251-263 have been discovered, all unilable; mass number 262 has the longest half-life (3.6 hours).

lawrencium

a transuranic element artificially produced from californium. Symbol: Lr; atomic no.: 103; half-life of most stable isotope, 256Lr: 35 seconds; valency: 3