Exradio
The Century Dictionary and Cyclopedia
noun.
The name proposed by Sir William Ramsay for the radioactive, gaseous product produced by radium salts, which was first observed in 1900 by Dorn and afterward more carefully investigated by Rutherford, who called it the
radium emanation.
Wiktionary, Creative Commons Attribution/Share-Alike License
noun.
Radon
.