atomic number 86

Noun
  1. 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 (synset 114676283)
    is a type of:
    • chemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
    • argonon, inert gas, noble gas - any of the chemically inert gaseous elements of the helium group in the periodic table
    same as: radon, rn

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