'''Radon''' is a [[noble gas]]. It is not to be confused with [[radium]], an [[alkali earth metal]]. The atomic weight of Radon-222, the most common isotope, is 222.0175777. | '''Radon''' is a [[noble gas]]. It is not to be confused with [[radium]], an [[alkali earth metal]]. The atomic weight of Radon-222, the most common isotope, is 222.0175777. |