Artificial radioactive decay series:

Isotopes are a set of nuclides whose atomic numbers (Z) are same but these have different mass numbers (A).  These may be stable and radioactive.  For example H has three isotopes, of which ¹H and ²H are stable and ³H is radioactive. Isobars are nuclides having the same mass number (A) but different atomic numbers (Z). Thus ¹²B, ¹²C and ¹²N have 5, 6 and 7 protons respectively.

Figure: Artificial radioactive decay series of 237Np also called (4n+1) neptunium series