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mendelevium (mĕndəlāvˈēəm), artificially produced radioactive chemical element; symbol Md; at. no. 101; mass no. of most stable isotope 258; m.p. 827℃; b.p. and sp. gr. unknown; valence +1, +2, +3. Mendelevium is a metal of the actinide series in Group 3 of the periodic table. The ninth transuranium element to be discovered, it is named for the Russian chemist Dmitri Ivanovich Mendeleev. The symbol Mv was used at first, but it was changed to Md in 1963. Sixteen isotopes of mendelevium are known. Mendelevium-256 (half-life about 76 min) was the first isotope produced; it was detected in 1955 by Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson, and Glenn T. Seaborg, who produced it one atom at a time by bombarding einsteinium-253 with alpha particles in a cyclotron at the Univ. of California at Berkeley. This technique of producing and detecting single atoms has become the standard for the discovery of the elements beyond mendelevium in the periodic table. Little is known of the properties of this element, since its isotopes are unstable and difficult to produce. Mendelevium-258 (the most stable isotope) has a half-life of 51.5 days; its synthesis (by bombarding einsteinium-255 with alpha particles) may make possible studies of the physical and chemical properties of the element.
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Synthetic radioactive element, symbol Md, with atomic number 101; made by bombarding lighter elements with light nuclei accelerated in cyclotrons.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
a transuranic element artificially produced by bombardment of einsteinium. Symbol: Md; atomic no.: 101; half-life of most stable isotope, 258Md: 60 days (approx.); valency: 2 or 3
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005