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Decay Scheme Uranium-238 (text description)

Radon comes from the decay of uranium, part of a series of 14 transformations, called a decay chain. This process takes several billion years to complete. At the end of its decay chain is lead 206 – a stable, non radioactive element.

As uranium undergoes radioactive decay, it emits alpha, beta and gamma radiation, along with a series of products that include radon. In turn, radon decays through a series of four very short-lived radioactive radon decay products, in the form of solid, electrically-charged particles that are called radon progeny: polonium-218, lead-214, bismuth-214, and polonium-214.

Because of their short half-lives, radon progeny emit radiation more quickly and present greater health risks than radon itself. The two that pose a health risk are polonium-218 and polonium-214.