---
title: "Oganesson (Og) — element 118"
description: "Oganesson is element 118, symbol Og, most stable isotope 294. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/oganesson/
site: "At One Place"
---

# Oganesson (Og)

**Oganesson — element 118: Og**

[294] · Noble gas · period 7, group 18

Oganesson is the heaviest element that exists, and there are thought to have been fewer than ten atoms of it, ever. It is in the noble gas column but is predicted to be neither noble nor a gas: relativistic effects should smear its electron shells into something closer to a uniform electron gas with no shell structure at all, making it reactive and probably a solid at room temperature. It is the second element named after a living person — Yuri Oganessian, who has led or co-led the discovery of more elements than anyone in history.

## Properties

- **Atomic number:** 118
- **Symbol:** Og
- **Mass number of most stable isotope:** [294]
- **Category:** Noble gas
- **Group:** 18
- **Period:** 7
- **Block:** p-block
- **Electron configuration:** [Rn] 7s² 5f¹⁴ 6d¹⁰ 7p⁶
- **Electrons per shell:** 2, 8, 18, 32, 32, 18, 8
- **Oxidation states:** 0, +2, +4, +6, -1
- **Discovered:** 2002 by Yuri Oganessian and colleagues at Dubna, with Lawrence Livermore

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
- **Noble gas shorthand:** [Rn] 7s² 5f¹⁴ 6d¹⁰ 7p⁶
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 18 · Q: 8

## What it is used for

- Research only; no application outside the laboratory

## Hazards

- Intensely radioactive; the longest-lived isotope survives for well under a second

> Melting point, boiling point, density and electronegativity are omitted: no measurement is possible on a handful of atoms lasting under a millisecond. The mass given is the mass number of oganesson-294, the only confirmed isotope, whose half-life is around 0.7 milliseconds. Named in 2016, completing period 7.

> Several physical properties are not listed for oganesson because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 116 | Livermorium | Lv | [293] |
| 117 | Tennessine | Ts | [294] |
| 118 | Oganesson ← | Og | [294] |

## Group 18

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Oganesson sits in group 18 with helium, neon, argon, krypton, xenon, radon.

## Common questions

### What is the atomic number of oganesson?

118. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for oganesson?

Og.

### What is the electron configuration of oganesson?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶, or [Rn] 7s² 5f¹⁴ 6d¹⁰ 7p⁶ in noble-gas shorthand.

## Related pages

- [Livermorium (Lv)](https://atoneplace.net/element/livermorium/)
- [Tennessine (Ts)](https://atoneplace.net/element/tennessine/)
- [Helium (He)](https://atoneplace.net/element/helium/)
- [Neon (Ne)](https://atoneplace.net/element/neon/)
- [Argon (Ar)](https://atoneplace.net/element/argon/)
- [Krypton (Kr)](https://atoneplace.net/element/krypton/)
- [Xenon (Xe)](https://atoneplace.net/element/xenon/)
- [Radon (Rn)](https://atoneplace.net/element/radon/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)