Og Oganesson

Quick answerOganesson (Og) is a noble gas with atomic number 118 and a mass number of 294 (the most stable isotope), in group 18, period 7. It was discovered by Yuri Oganessian and colleagues in 2006. It is used for superheavy element research and testing the island of stability. Its electron configuration is [Rn] 5f14 6d10 7s2 7p6 (predicted).

Oganesson is the heaviest element ever made, named for physicist Yuri Oganessian while he was still alive.

Key facts

Symbol	Og
Atomic number	118
Atomic mass	[294] — mass number of the most stable isotope
Category	noble gas
Group	18
Period	7
Block	p-block
Electron configuration	[Rn] 5f14 6d10 7s2 7p6 predicted
Discovered	Yuri Oganessian and colleagues, 2006
Uses	superheavy element research, testing the island of stability

Quick quiz

Three questions from the facts on this page. No sign-up, no score is saved.

1. What is the chemical symbol of Oganesson?

He Og Ne Ar

2. What is the atomic number of Oganesson?

119 118 117 120

3. Which category does Oganesson belong to?

halogen alkali metal transition metal noble gas

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Keep exploring

• Periodic table — all 118 elements
• Helium (He) — another noble gas, atomic number 2
• Neon (Ne) — another noble gas, atomic number 10
• Argon (Ar) — another noble gas, atomic number 18
• Krypton (Kr) — another noble gas, atomic number 36
• Xenon (Xe) — another noble gas, atomic number 54
• Radon (Rn) — another noble gas, atomic number 86

Sources & last updated

• CIAAW — Standard Atomic Weights
• PubChem Periodic Table
• Wikipedia — Timeline of chemical element discoveries
• Wikipedia — Oganesson

Last updated: 2026-11-12. Figures are shown with their year; where sources disagree, the value is left out rather than estimated.