#noble_gas__noblega__inert_gas__inertga  any of the chemically inert gaseous elements of the helium group in the periodic table
  supertype:  #chemical_element  #gas
  subtype:  #argon__ar__atomic_number_18  a colorless and odorless inert gas; one of the six inert gases; comprises approximately 1% of the earth's atmosphere
  subtype:  #helium__He__atomic_number_2  a very light colorless element that is one of the six inert gasses; the most difficult gas to liquefy; occurs in economically extractable amounts in certain natural gases (as those found in Texas and Kansas)
  subtype:  #krypton__Kr  a colorless element that is one of the six inert gasses; occurs in trace amounts in air
  subtype:  #neon__Ne__atomic_number_10  a colorless odorless gaseous element that give a red glow in a vacuum tube; one of the six inert gasses; occurs in the air in small amounts
  subtype:  #radon__Rn__atomic_number_86  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
  subtype:  #xenon__Xe__atomic_number_54  a colorless odorless inert gaseous element occurring in the earth's atmosphere in trace amounts

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