Which chemical element of Group 18 of the periodic table is produced by the natural radioactive decay of uranium in soils and rocks?

Explanation

Radon-222 is produced through the uranium-238 decay chain: uranium eventually gives rise to radium-226, which decays to radon-222. Radon is a radioactive Group 18 gas that can escape from soils and rocks. The process is a decay chain, rather than a direct one-step uranium-to-radon conversion.