ABSTRACT
A nucleus of the atomic number Z and the mass number A consists of Z protons and N = A – Z neutrons. The mass number A is the sum of nucleons (protons and neutrons) in a nucleus. A nucleus identi‚ed by A and Z is called a nuclide. The notation of a nuclide is E,ZA in which E is an element, for example, O.816 At the present time, there exist about 300 stable nuclides and about 1,700 unstable radioactive nuclides. The classi‚cation of nuclides is as follows:
1. Isotope has the same Z. Chemical properties are the same because the number of orbital electrons and that of electron con‚gurations are the same. Radioisotopes are unstable in energy; therefore, a nuclide decays to another nuclide by emitting radiation. This ability is called radioactivity.
