meitnerium

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meitnerium

(mītnĭr`ēəm), artificially produced radioactive chemical element; symbol Mt; at. no. 109; mass number of most stable isotope 276; m.p., b.p., sp. gr., and valence unknown. Situated in Group 9 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 is expected to have properties similar to those of iridiumiridium
, metallic chemical element; symbol Ir; at. no. 77; at. wt. 192.217; m.p. about 2,410°C;; b.p. about 4,130°C;; sp. gr. 22.55 at 20°C;; valence +3 or +4.
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.

In 1982 a German research team led by P. Armbruster and G. Münzenberg at the Institute for Heavy Ion Research at Darmstadt bombarded bismuth-209 atoms with iron-58 ions. On the tenth day of the experiment, one atom was unambiguously identified as an isotope of element 109 with mass number 266 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 3.4 msec. The Germans suggested the name meitnerium to honor the Austrian-Swedish physicist and mathematician Lise MeitnerMeitner, Lise
, 1878–1968, Austrian-Swedish physicist and mathematician. She was professor at the Univ. of Berlin (1926–33). A refugee from Germany after 1938, she became associated with the Univ. of Stockholm and with the Nobel Institute at Stockholm.
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. This name was recognized internationally in 1997. The most stable isotope of meitnerium, meitnerium-276, has a half-life of 0.72 sec.

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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; transuranium elementstransuranium 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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.

meitnerium

[mīt′nir·ē·əm]
(chemistry)
A chemical element, symbolized Mt, atomic number 109, a synthetic element; the seventeenth transuranium element.

meitnerium

a synthetic element produced in small quantities by high-energy ion bombardment. Symbol: Mt; atomic no.: 109