18th Group
-     Default:He, Ne, Ar, Kr, Xe, Rd 
-     Molecules: 0 bond is accepted. -     Exceptions: The following xenon compounds are accepted: XeF2, XeF4, XeF6, XeO3, XeO4 XeOF4, XeO2F2, XeO3F2. 
 
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-     Ions: 0 charge is accepted 
-     Radicals: 0 radical is accepted