1 文書を見つけるための辞書。

• rn, atomic number 86, radon
• ラドン
• a radioactive gaseous element formed by the disintegration of radium; the heaviest of the inert gasses; occurs naturally (especially in areas over granite) and is considered a hazard to health
• ラジウムの崩壊で形成された放射性ガスの要素