Radon Radon was discovered while studying the natural radioactive decay of radium . Finding that radium decays to radon which, in turn, decays to polonium was a key element in the discovery that radioactive elements are transmuted into lighter elements.
Radon is at the bottom of the column of noble gases .
It is a naturally radioactive, odorless, colorless gas. It can be detected by a Geiger counter. Radon decays into radioactive polonium and alpha radiation . This radiation makes radon useful in cancer therapy.