Unit of activityActivity is the term used to characterise the number of nucl... of a radionuclideUnstable nuclide spontaneously decaying without external eff... named after Henri Becquerel who first discovered radioactivityProperty of certain substances to convert without external e.... Symbol: BqSymbol for becquerel, the name of the unit for activity.. The activityActivity is the term used to characterise the number of nucl... is equal to 1 becquerel if 1 nucleusPositively charged nucleus of an atom. Its diameter amounts ... decays per second in the present quantity of a radionuclideUnstable nuclide spontaneously decaying without external eff.... The unit replaces the former unit curieName for the former unit of activity. The activity of 1 curi.... Also see ‘curie’