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artificially produced radioactive chemical element; symbol Ds; at. no. 110; mass number of most stable isotope 281; m.p., b.p., sp. gr., and valence unknown. Situated in Group 10 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 platinumplatinum
, metallic chemical element; symbol Pt; at. no. 78; at. wt. 195.084; m.p. 1,772°C;; b.p. 3,827±100°C;; sp. gr. 21.45 at 20°C;; valence +2 or +4.
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In 1994 an international research team led by Peter Armbruster and Sigurd Hofmann at the Institute for Heavy Ion Research at Darmstadt, Germany, bombarded lead-208 atoms with nickel-62 ions. In a two-week experiment, four atoms were unambiguously identified as an isotope of element 110 with mass number 269 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 0.17 msec. In a separate experiment, again using the lead-208 target but bombarding it with nickel-64 ions, the same team created nine atoms of an element 110 isotope with mass number 271 and a half-life of 1.4 msec. Six isotopes have been synthesized and unambiguously identified. The Germans suggested the name darmstadtium to honor Darmstadt, where their institute is located. This name was recognized internationally in 2003. The most stable isotope, darmstadtium-281, has a half-life of approximately 11 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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; 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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; 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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References in periodicals archive ?
Mean UUN in Japanese Black cows was 676 mg/dl, ranging from 126 to 1,430 mg/dl, and mean PUN was 15.
Maag uun (coconut), another Tai word, is no longer used by most Tai, some of whom do not even know the term.
The 24 UUN is useful in calculating protein needs and estimating the level of physiologic stress.
Note the lack of the clitic me with the verb forms uun, kelun and kolten.