'nənkwäd`ēəm), artificially produced radioactive chemical element element, in chemistry, a substance that cannot be decomposed into simpler substances by chemical means. A substance such as a compound can be decomposed into its constituent elements by means of a chemical reaction, but no further simplification can be achieved...... Click the link for more information. ; symbol Uuq; at. no. 114; mass number of most stable isotope isotope , in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F.
..... Click the link for more information. 289; m.p., b.p., sp. gr., and valence unknown. Situated in Group 14 of the periodic table periodic 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
..... Click the link for more information. , it is expected to have properties similar to those of lead lead, metallic chemical element; symbol Pb [Lat. plumbum]; at. no. 82; at. wt. 207.2; m.p. 327.502°C;; b.p. about 1,740°C;; sp. gr. 11.35 at 20°C;; valence +2 or +4.
..... Click the link for more information. and tin tin, metallic chemical element; symbol Sn [Lat. stannum]; at. no. 50; at. wt. 118.69; m.p. 231.9681°C;; b.p. 2,270°C;; sp. gr. 5.75 (gray), 7.3 (white); valence +2 or +4. Tin exhibits allotropy; above 13.
..... Click the link for more information. .
Late in Dec., 1998, using plutonium-244 and calcium-48 isotopes provided by the Lawrence Berkeley National Laboratory in Calif., Russian scientists employed a cyclotron at the Joint Institute for Nuclear Research in Dubna to produce an atom of element 114 with a mass number of 289. After a surprisingly long existence of 30 seconds, the ununquadium atom broke down successively into ununbium ununbium , artificially produced radioactive chemical element; symbol Uub; at. no. 112; mass number of most stable isotope 285; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. (element 112), darmstadtium darmstadtium, artificially produced radioactive chemical element; symbol Ds; at. no. 110; mass number of most stable isotope 271; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. (element 110), and hassium hassium , artificially produced radioactive chemical element; symbol Hs; at. no. 108; mass number of most stable isotope 265; m.p., b.p., sp. gr., and valence unknown.
..... Click the link for more information. (element 108). The Dubna team created a second isotope of ununquadium, Uuq-287, with a half-life measured in milliseconds, three months later.
Ununquadium is the first element of what might be an "island of stability" among heavy nuclei. Synthetic elements heavier than uranium are generally unstable. Scientists have for some time thought that elements number 114 and above might possess a very stable configuration of neutrons and protons because the nucleus would have a full complement of protons and neutrons making for longer life. The Dubna and Berkeley results seem to be evidence for this, since each isotope having an increasing number of neutrons (toward the optimum 184) has a longer half-life.
No name has yet been adopted for element 114, which is therefore called ununquadium, from the Latin roots un for one and quad for four, under a convention for neutral temporary names proposed by the International Union of Pure and Applied Chemistry (IUPAC) in 1980.
See also synthetic elements synthetic 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.
..... Click the link for more information. ; transactinide elements transactinide 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.
..... Click the link for more information. ; transuranium elements transuranium 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.
..... Click the link for more information. .
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