(under the class definition) Products or processes in which the product is a noble or inert gas having atomic nos. 2, 10, 18, 36, or 54, or a compound thereof; the gas being a member of the "zero" group of the periodic table, having no valency and combining with other elements only with difficulty.
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249, for radon (atomic no. 86), which is the radioactive member of the noble or inert gases, or a compound thereof.
