Chemical element, symbol Og and atomic number 118 / From Wikipedia, the free encyclopedia

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Oganesson is a synthetic chemical element; it has symbol Og and atomic number 118. It was first synthesized in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, near Moscow, Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by the Joint Working Party of the international scientific bodies IUPAC and IUPAP. It was formally named on 28 November 2016.[15][16] The name honors the nuclear physicist Yuri Oganessian, who played a leading role in the discovery of the heaviest elements in the periodic table. It is one of only two elements named after a person who was alive at the time of naming, the other being seaborgium, and the only element whose eponym is alive as of 2024.[17][lower-alpha 1]

Quick facts: Oganesson, Pronunciation, Appearance, Mass nu...
Oganesson, 118Og
Appearancemetallic (predicted)
Mass number[294]
Oganesson in the periodic table


Atomic number (Z)118
Groupgroup 18 (noble gases)
Periodperiod 7
Block  p-block
Electron configuration[Rn] 5f14 6d10 7s2 7p6 (predicted)[3][4]
Electrons per shell2, 8, 18, 32, 32, 18, 8 (predicted)
Physical properties
Phase at STPsolid (predicted)[5]
Melting point325 ± 15 K (52 ± 15 °C, 125 ± 27 °F) (predicted)[5]
Boiling point450 ± 10 K (177 ± 10 °C, 350 ± 18 °F) (predicted)[5]
Density (near r.t.)7.2 g/cm3 (solid, 319 K, calculated)[5]
when liquid (at m.p.)6.6 g/cm3 (liquid, 327 K, calculated)[5]
Atomic properties
Oxidation states(−1),[4] (0), (+1),[6] (+2),[7] (+4),[7] (+6)[4] (predicted)
Ionization energies
  • 1st: 860 kJ/mol (calculated)[8]
  • 2nd: 1560 kJ/mol (calculated)[8]
Atomic radiusempirical: 152 pm (predicted)[9]
Covalent radius157 pm (predicted)[10]
Other properties
Natural occurrencesynthetic
Crystal structure face-centered cubic (fcc)
Face-centered cubic crystal structure for oganesson

CAS Number54144-19-3
Namingafter Yuri Oganessian
PredictionHans Peter Jørgen Julius Thomsen (1895)
DiscoveryJoint Institute for Nuclear Research and Lawrence Livermore National Laboratory (2002)
Isotopes of oganesson
Main isotopes[12] Decay
abun­dance half-life (t1/2) mode pro­duct
294Og synth 0.7 ms[13][14] α 290Lv
Symbol_category_class.svg Category: Oganesson
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Oganesson has the highest atomic number and highest atomic mass of all known elements as of 2024. On the periodic table of the elements it is a p-block element, a member of group 18 and the last member of period 7. Its only known isotope, oganesson-294, is highly radioactive, with a half-life of 0.7 ms and, as of 2020, only five atoms have been successfully produced.[19] This has so far prevented any experimental studies of its chemistry. Because of relativistic effects, theoretical studies predict that it would be a solid at room temperature, and significantly reactive,[19][3] unlike the other members of group 18 (the noble gases).

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