Oganesson (Og)

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

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.