Oganesson is IUPAC's name for the transactinide element with the atomic number 118 and element symbol Og. It is also known as eka-radon or element 118, and on the periodic table of the elements it is a p-block element and the last one of the 7th period. Oganesson is currently the only synthetic member of group 18.
Three reasons Oganesson stands out
1
Named after Armenian-Russian nuclear physicist who led the discovery of many elements.
2
It belongs to the group usually known for being reluctant to react.
3
Despite being classified as a noble gas, it is predicted to be a solid at room temperature and potentially highly reactive.
The table’s heaviest confirmed endpoint
Oganesson completes period seven and honors nuclear physicist Yuri Oganessian. Although placed with the noble gases, theory predicts a highly polarizable element that may be a solid and considerably more reactive than neon or argon. For now, those ideas await experiments on longer-lived isotopes.
Recognizing Oganesson in Elementle
If Oganesson is the mystery element, guesses below atomic number 118 point up and guesses above it point down. Its symbol is Og: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for noble gas guesses. Compare Radon (Rn), number 86 and Xenon (Xe), number 54: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.