What factors determine nuclear stability?

Hint :The stability of an atom's nucleus is referred to as nuclear stability. A stable nucleus does not degrade on its own. Stable nuclei are found in radioactive elements, which decay naturally, releasing a variety of radiations.

Complete Step By Step Answer:
Nuclear stability is a principle that helps in determining an isotope's stability. The neutron/proton ratio and the overall number of nucleons in the nucleus are the two major factors that determine nuclear stability.
As compared to the periodic table, an isotope is an element with the same atomic number but a different atomic mass.
$1)$ Neutron or proton ratio
The neutron to proton ratio is the most important factor in deciding when a nucleus is stable. The nuclei of elements with $\left( {Z < 20} \right)$ are smaller, and their nuclei have a ratio of $1:1$ , preferring to have equal number of protons and neutrons.
With atomic numbers ranging from $20$ to $83$ , heavy atoms have a different ratio than light elements. The difference between the ratios is the repulsive force between protons: the more significant the repulsive force is, the greater the neutrons needed to stabilize the nuclei.
$2)$Number of nucleons
There is no stable nucleus greater than lead$ - 208$ . This is because, despite being $100$ times stronger than electrostatic repulsions, the strong nuclear force only acts for very short distances. The powerful force will no longer tie a nucleus together until it has developed to a certain size.

Note :
 The number of nucleons in a nuclear atom determines its stability (neutrons and protons). To keep the nucleus intact, the nucleons interfere with each other through the strong nuclear force, which must counteract the electrostatic repulsion between the protons. Since a nucleus is unstable, radioactive decay occurs.