ElementsWhat is oganesson?
Oganesson is a radioactive element and the heaviest made so far. Only a handful of atoms have ever been produced.
What is oganesson used for?
Research only.
Where the name comes from
In honour of the physicist Yuri Oganessian. The name was approved in 2016.
Key facts
- Symbol
- Og
- Atomic number
- 118
- Atomic mass
- 295.216 u
- Family
- Noble gas
- Period
- 7
- Group
- 18
- Block
- p
- State at room temperature
- Gas (expected)
- Melting point
- not measured
- Boiling point
- not measured
- Density
- not measured
- Electrons per shell
- 2, 8, 18, 32, 32, 18, 8
- Electron configuration
- [Rn]7s2 7p6 5f14 6d10
- Common oxidation states
- +6, +4, +2, +1, 0, -1
- Electronegativity (Pauling)
- no value
- First ionisation energy
- not measured
- Electron affinity
- no value
- Atomic radius (van der Waals)
- no value
- Discovered
- 2006
Place in the periodic table
Oganesson is element number 118. It sits in period 7 (row 7) of the periodic table, in group 18 (column 18), and belongs to the p-block. It is the last element known so far. Just before it comes tennessine (117). In the same column, radon is above it. Elements in one column tend to behave alike.
Family: Noble gases.
Physical properties
Too few atoms of oganesson have been made to measure its bulk properties. It is expected to be a gas at room temperature.
Inside the atom
An atom of oganesson has 118 protons in its nucleus and, when neutral, 118 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 32, 18, 8. The outermost shell holds 8 electrons. Written in full, the electron configuration is [Rn]7s2 7p6 5f14 6d10 (predicted).
One mole of oganesson weighs 295.216 grams, so a single gram contains about 2.04 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains oganesson with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.