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Oganesson
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<p>Oganesson is a <a href="/facts/Synthetic_element/azU9Nr1m">synthetic chemical element</a>; it has <a href="/facts/Chemical_symbol/2Fe1VAL0">symbol</a> Og and <a href="/facts/Atomic_number/bgAr581S">atomic number</a> 118. It was first synthesized in 2002 at the <a href="/facts/Joint_Institute_for_Nuclear_Research/JrSF8sQQ">Joint Institute for Nuclear Research</a> (JINR) in <a href="/facts/Dubna/mn37rc4l">Dubna</a>, near <a href="/facts/Moscow/AcFYpQUR">Moscow</a>, Russia, by a joint team of Russian and American scientists. In December 2015, it was recognized as one of four new elements by the <a href="/facts/IUPAC%2fIUPAP_Joint_Working_Party/1mKaf9UW">Joint Working Party</a> of the international scientific bodies <a href="/facts/IUPAC/2AV6myCK">IUPAC</a> and <a href="/facts/IUPAP/ah3BodlS">IUPAP</a>. It was formally named on 28 November 2016. The name honors the nuclear physicist <a href="/facts/Yuri_Oganessian/69TJ9VyW">Yuri Oganessian</a>, who played a leading role in the discovery of the heaviest elements in the periodic table </p><p>Oganesson has the highest atomic number and highest <a href="/facts/Atomic_mass/J1FJY9MV">atomic mass</a> of all <a href="/facts/List_of_chemical_elements/8hWI5T7K">known elements</a>. On the periodic table of the elements it is a <a href="/facts/P-block/BbzD5jUU">p-block</a> element, a member of <a href="/facts/Noble_gas/j0yHMEAE">group 18</a> and the last member of <a href="/facts/Period_7/H5QuVHGQ">period 7</a>. Its only known isotope, <a href="/facts/Isotopes_of_oganesson/pkoyugEy">oganesson-294</a>, is highly <a href="/facts/Radioactive_decay/Ya6FVjt4">radioactive</a>, with a half-life of 0.7 <a href="/facts/Millisecond/xHCyv235">ms</a> and, as of 2025, only five atoms have been successfully produced. This has so far prevented any experimental studies of its chemistry. Because of <a href="/facts/Relativistic_quantum_chemistry/8A1se1CS">relativistic effects</a>, theoretical studies predict that it would be a <a href="/facts/Solid/YU0hJq6f">solid</a> at <a href="/facts/Standard_temperature_and_pressure/JhJv9KFJ">room temperature</a>, and significantly reactive, unlike the other members of group 18 (the <a href="/facts/Noble_gas/j0yHMEAE">noble gases</a>). </p>