Atomic number 118 · Noble gas
Oganesson Og
Oganesson is the heaviest element known and has the highest atomic number, closing period 7 of the periodic table. It sits at the bottom of group 18, the noble gases. Only about five atoms have ever been detected, and each survived for less than a millisecond.
Key properties
| Atomic number | 118 |
|---|---|
| Atomic weight | [294] (No stable isotope; mass number of a representative isotope in brackets) |
| Category | Noble gas |
| Group | 18 |
| Period | 7 |
| Block | p |
| State (25 °C, 1 atm) | Gas (Predicted) |
| Melting point | — |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | — |
| First ionization energy | — |
| Electron affinity | — |
| Oxidation states | +6, +4, +2, +1, 0, -1 |
| Discovered | 2006 |
Electron configuration
- Condensed
- [Rn]7s2 7p6 5f14 6d10
- Full
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d10 7s2 7p6
- Electrons per shell
- 2 · 8 · 18 · 32 · 32 · 18 · 8
Orbital diagram
Electron configurations of some superheavy elements (beyond 103) are theoretical predictions.
Position in the table
Discovery
In 1999 a Berkeley team announced the discovery of element 118, but other laboratories could not reproduce it, and an investigation announced in 2002 found that the data had been fabricated by one researcher. The claim was retracted.
The first genuine observation came in 2002 at the Joint Institute for Nuclear Research in Dubna. A Dubna–Livermore team led by Yuri Oganessian bombarded a californium-249 target with calcium-48 ions. Together with further runs in 2005, they identified three or four atoms of oganesson-294 and announced the result in October 2006. IUPAC recognised the discovery in December 2015, and the name was approved on 28 November 2016.
Origin of the name
The element honours Yuri Oganessian, the Russian nuclear physicist of Armenian descent who led the synthesis of the heaviest elements. It is only the second element, after seaborgium, named after a living person. Following the pattern of the noble gases (neon, argon, krypton, xenon, radon), it takes the ending -on. The symbol is Og.
Main uses
- Basic research: It has no uses outside science.
- The end of the table: Although it belongs to group 18, relativistic effects are predicted to make it a solid rather than a gas at room temperature and noticeably reactive, unlike the other noble gases. It tests how far the periodic table's patterns hold.
- Experiments aiming at element 119 and beyond are under way in several countries; success would open period 8.
Isotopes
There are no stable isotopes. The only known isotope is oganesson-294, with a half-life of about 0.7 milliseconds. It alpha-decays into livermorium-290.
In everyday life
It does not exist in nature; only a few atoms at a time are made in accelerators and they decay almost immediately, so it has no connection with daily life or health.
Good to know
- Oganesson has the highest atomic number and atomic mass of any known element.
- Only about five atoms have ever been detected.
- It is the second element named after a living person.
Same group (18)
Data sources · Properties: PubChem Periodic Table (US NIH/NLM public data) · Atomic weights: CIAAW 2024 abridged standard atomic weights · Names: Wikidata (CC0); Korean names follow the Korean Chemical Society. Retrieved 2026-09-23.