R1A1D2I1O1A1C3T1I1V4I1T1Y4
22 points
RADIOACTIVITY is validvalid
the quality of being radioactive [n RADIOACTIVITIES]
the spontaneous decay of the nucleus of an element [n RADIOACTIVITIES]
the quality of being radioactive [n RADIOACTIVITIES]
the spontaneous decay of the nucleus of an element [n RADIOACTIVITIES]