atomic number 86

Từ điển WordNet v3.1 - WordNet Dictionary

noun

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
• Syn:
radon, Rn
• Hypernyms:
chemical element, element, noble gas, inert gas, argonon