Radon - Rn

Radon — chemical properties and water context

Radon is a colourless, odourless radioactive noble gas. Radon-222 can dissolve in groundwater and may be released from water into indoor air during normal use.

Atomic number	86
Representative isotope mass number	[222]
Density	0.009074 g/cm3 (gas)
Melting point	−71 °C
Boiling point	−61.7 °C
Electron configuration	[Xe] 4f14 5d10 6s2 6p6

Chemical properties

Radon is in Group 18 and Period 6. It is chemically unreactive and radioactive; the representative mass number shown is for radon-222, not a standard atomic weight. Radon-222 has a half-life of about 3.8 days and decays through a series of radioactive progeny.

Uses and applications

Radon has no common modern industrial use. Its main relevance to water professionals is as a naturally occurring radionuclide in some groundwater, especially where local geology contains uranium-bearing minerals.

Radon in water treatment

The World Health Organization identifies aeration and granular activated carbon as methods for reducing radon in drinking water. Aeration transfers radon from water to air, so off-gas must be considered; activated carbon can accumulate radioactivity and requires appropriate monitoring and residual management. Because dissolved radon can enter indoor air during water use, assessment should consider both water and indoor-air pathways.

Environmental and health context

Radon is radioactive and presents its main health concern through inhalation of radon and its decay products. Measure water activity using a suitable method and follow local radiological guidance. Do not infer a safe indoor-air condition solely from a water test.

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