Q.How does N/Z ratio affect the nuclear stability? Explain with a suitable diagram.

Step 1. Plotting the neutron number N (vertical axis) against the proton number Z (horizontal axis) for every known stable nuclide does not scatter randomly -- the points trace a narrow diagonal band, the belt (or zone) of stability.

Step 2. For light nuclei, lighter than 40-20-Ca, this belt tracks very close to the straight reference line N=Z, i.e. stable light nuclides have close to equal numbers of protons and neutrons (N/Z ≈ 1).

Step 3. For nuclei heavier than calcium, the belt curves progressively away from the N=Z line, with N/Z climbing steadily above 1 as A increases.

Step 4. The physical reason: as more protons are packed into a heavier nucleus, the total electrostatic (coulombic) repulsion among them grows large. Extra neutrons help by physically separating the protons on average and by contributing extra short-range attractive nuclear force without adding any extra repulsion -- so a growing surplus of neutrons over protons is needed to keep a heavier nucleus bound. …

Describe the N-vs-Z stability-belt plot, contrast the light-nuclide (N/Z≈1) and heavy-nuclide (N/Z>1) regions, and explai …

• Stating N/Z is always close to 1 for ALL stable nuclides, missing that it climbs above 1 for heavier ones. …