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Radon

Element 86 · Noble gas

Specimen

Atomic number
86
Atomic mass
222.018
State at room temperature
Gas
Melting point
-71.15 °C
Boiling point
-61.7 °C
Density
0.00973 g/cm³
Discovered
1900

Physical data from PubChem.1

Can I eat it?

In food and water
Radioactive. Radon is a radioactive gas from rocks and soil. Some well water contains it, but most of the dose comes from breathing it. The WHO names radon as one of the leading causes of lung cancer. 2

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The atom

Rn
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 18
6 (P) outermost 8
Total86

Configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶

4f ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓
5d ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓
6s ↑ ↓
6p ↑ ↓ ↑ ↓ ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 86 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Xe core, with one arrow per electron.

Related elements

Group 18
He Helium Ne Neon Ar Argon Kr Krypton Xe Xenon Og Oganesson

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Sources

  1. 1

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Atomic mass, electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  2. 2

    World Health Organization, 2023. Radon .

    • Radon is one of the leading causes of lung cancer.
    • Radon dissolved in drinking-water is released into indoor air. Normally, a higher radon dose is received from inhaling radon compared with ingestion.