- Oganesson (Og) is a synthetic, radioactive element with atomic number 118, and it currently holds the position as the heaviest known element on the periodic table.
- It belongs to Group 18, the noble gases, directly beneath radon. However, unlike lighter noble gases such as helium, neon, or argon, oganesson is not expected to behave as a typical inert gas.
- Its predicted electron configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶, suggesting a complete outer shell. Despite this, relativistic effects are so strong in oganesson that the 7p orbitals expand and destabilize, reducing the noble-gas-like inertness and potentially giving it chemical reactivity. The atom contains one hundred and eighteen protons, about one hundred and seventy-six to one hundred and seventy-nine neutrons depending on the isotope, and one hundred and eighteen electrons distributed across seven shells.
- The most stable isotope synthesized so far is oganesson-294 (²⁹⁴Og), with a half-life of approximately 0.89 milliseconds, making it one of the shortest-lived elements ever produced.
- Oganesson was first synthesized on July 9, 2002, at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, in collaboration with the Lawrence Livermore National Laboratory (LLNL) in the United States. Scientists bombarded a target of californium-249 (²⁴⁹Cf) with calcium-48 (⁴⁸Ca) ions, producing a few atoms of oganesson-294 (²⁹⁴Og). The identification was confirmed through observed alpha decay chains leading to known isotopes of lighter elements.
- The element was named oganesson in honor of the Russian nuclear physicist Yuri Oganessian, who made pioneering contributions to the discovery of superheavy elements. It is one of only two elements named after a living scientist (the other being seaborgium, named after Glenn T. Seaborg). The name and symbol Og were officially approved by IUPAC in 2016.
- Oganesson has no known uses outside of fundamental research, as it can only be produced in particle accelerators in atom-scale amounts and decays almost instantly. Its importance lies in expanding the limits of the periodic table, testing nuclear physics theories, and exploring the region near the hypothesized “island of stability.”
- Chemically, oganesson is predicted to deviate strongly from the behavior of lighter noble gases. Instead of being a colorless, monatomic gas, it is expected to be a solid under standard conditions due to strong interatomic forces (van der Waals and relativistic effects). It may even exhibit metallic or semiconductor-like properties, unlike the inert gases above it. The +2 oxidation state is considered possible, and some calculations predict compounds such as oganesson difluoride (OgF₂). Thus, oganesson may behave more like a metalloid or a reactive heavy element than a noble gas.
- Biologically, oganesson has no role and would be highly radiotoxic. However, its extremely short half-life ensures it has no meaningful interaction with biological systems.
- Environmentally, oganesson does not occur in nature. It exists only when synthesized artificially in laboratories and disappears in less than a millisecond, leaving no trace.
