Q.Referring the stability belt of stable nuclides, which nuclides are -β and +β emitters? Why?

Step 1. The stability belt is the narrow zone traced out by all stable nuclides when N is plotted against Z; any nuclide off the belt is radioactive.

Step 2. A nuclide lying ABOVE the belt has too many neutrons relative to protons for its mass number (it is neutron-rich). Beta-minus (β-) decay converts a neutron into a proton (emitting an electron), which lowers N by 1 and raises Z by 1 -- moving the nuclide's (Z,N) point diagonally down-and-right, back toward the belt. So neutron-rich, above-the-belt nuclides are β- emitters. …

Work out, for a nuclide off the belt in each direction, which decay mode changes N and Z in the direction …

• Reversing the two cases (assigning β- to proton-rich nuclides or β+ to neutron-rich ones).
• Forgetting that alpha decay (not asked about here) is the typical mode instead for very heav …