oganesson


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oganesson

(ō`gənĕs'ən), artificially produced radioactive chemical elementelement,
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.
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; symbol Og; at. no. 118; mass number of most stable isotopeisotope
, 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.
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 294; m.p., b.p., sp. gr., and valence unknown. Situated in Group 18 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 classed as an inert gasinert gas
or noble gas,
any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon, argon, krypton, xenon, and radon. They are colorless, odorless, tasteless gases and were once believed to be entirely inert, i.e.
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 and is expected to have properties similar to those of radonradon
, gaseous radioactive chemical element; symbol Rn; at. no. 86; mass no. of most stable isotope 222; m.p. about −71°C;; b.p. −61.8°C;; density 9.73 grams per liter at STP; valence usually 0. Radon is colorless and the most dense gas known.
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 and xenonxenon
[Gr.,=strange], gaseous chemical element; symbol Xe; at. no. 54; at. wt. 131.293; m.p. −111.9°C;; b.p. −107.1°C;; density 5.86 grams per liter at STP; valence usually 0. Xenon is a rare, colorless, odorless, tasteless, chemically unreactive gas.
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, but its electrons may be more nebulously associated with discrete shells, and it may as a result be chemically reactive. Scientists from the Joint Institute for Nuclear Research in Dubna, Russia, and Lawrence Livermore National Laboratory in California collaborated in the discovery of oganesson in experiments conducted in 2002 and 2005; the discovery was confirmed by the International Union of Pure and Applied Chemistry (IUPAC) in 2015. They bombarded atoms of californiumcalifornium
[from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900°C;; b.p. about 1,470°C;; density unknown; valence +3.
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-249 with ions of calciumcalcium
[Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839°C;; b.p. 1,484°C;; sp. gr. 1.55 at 20°C;; valence +2. Calcium is a malleable, ductile, silver-white, relatively soft metal with face-centered, cubic crystalline
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-48. Among the products of the bombardments were atoms of oganesson-294 (one in 2002, two in 2005), each of which decayed into an atom of livermoriumlivermorium,
artificially produced radioactive chemical element; symbol Lv; at. no. 116; mass number of most stable isotope 292; m.p., b.p., sp. gr., and valence unknown.
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 by emitting an alpha particlealpha particle,
one of the three types of radiation resulting from natural radioactivity. Alpha radiation (or alpha rays) was distinguished and named by E. R. Rutherford in 1909, who found by measuring the charge and mass of alpha particles that they are the nuclei of ordinary
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. Og-294 has a half-life of approximately 0.89 msec. The name oganesson, in honor of Russian physicist Yuri OganessianOganessian, Yuri Tsolakovich,
1933–, b. Rostov-na-Donu, Russian nuclear physicist, Ph.D. Moscow State Univ. (1963), Joint Institute for Nuclear Research (JINR), Dubna (1970).
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, was proposed for the element by its discoverers and approved by IUPAC in 2016.

In 1999 a research team at the Lawrence Berkeley National Laboratory in Calif. bombarded lead-208 atoms with high-energy krypton-86 ions to create what an analysis showed to be three atoms of element 118 with mass number 293 and a half-life of less than a millisecond. In 2001, however, the team retracted its claim to have produced the element after other laboratories failed to reproduce their results and after a reanalysis of the original data did not show the production of it. A subsequent investigation suggested that the original finding was the result of fraud on the part of one of the team scientists.

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 ?
For the ones heavier than oganesson, this might be so quick that it prevents them from having enough time to attract and capture an electron to form an atom.
The four elements confirmed by the International Union of Pure and Applied Chemistry are Nihonium (Nh), Moscovium (Mc), Tennessine (Ts) and Oganesson (Og).
Element 118 will be named oganesson, or Og, after Yuri Oganessian, a Russian physicist who contributed to the discovery of several superheavy elements.