Skip to content
Material World
Element · Rn

Radon

A radioactive gas produced by ordinary rock, and the reason geology turns up in building regulations.

Radon is a noble gas, chemically almost inert, and continuously produced by the decay of uranium present in ordinary rock and soil. Because it is a gas it does not stay where it forms: it moves through pore space and fractures, and accumulates in enclosed spaces above.

That makes radon unusual among hazards. It is not introduced by industry, it is not a contaminant of anything, and the amount in a building depends mainly on what the building stands on.

How it forms

Radon forms in the uranium decay chain and has a half-life of a few days — long enough to travel out of the rock that produced it, short enough that it decays where it collects. Granite terrain generally produces more than limestone or clay, because granite carries more uranium.

Environmental impact

Radon is the main source of natural radiation exposure for most people, and the risk comes from its solid decay products, which lodge in the lung rather than being breathed back out. Mitigation is a matter of ventilation and of sealing the path from ground to interior, which is why radon appears in building codes and in the surveys done before construction.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is sourced from

is found in

  • Air — material · in traces, and variable: it is a decay product of uranium in the ground rather than a permanent constituent, and it accumulates indoors, which is where it is a health problem rather than a curiosity

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Questions this page answers

Where it comes from, and what it becomes

Follow Radon back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Radon → is sourced from → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Radon → is sourced from → Uranium → is extracted from (the principal uranium ore, and the pitchblende the Curies worked) → Uraninite
  • Radon → is sourced from → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (a carbonate dissolves straight into acid, which is why an oxidised orebody goes to a leach pad and the sulfide beneath it goes to a smelter) → Malachite
  • Radon → is sourced from → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (leached with acid or alkali depending on the host rock, which is what decides the flowsheet of a uranium mill) → Uraninite