Why is a larger nucleus generally less stable than a smaller nucleus?

A larger nucleus is generally less stable than a smaller nucleus because the electric force of repulsion between protons is a long range force, while the attractive strong nuclear force is short-range. Repulsion is therefore large for the large nuclei. To bring about more explanation; if an atom is small then its nucleus is also small, in small nucleus, the distances between nuclear particles are very, very small due to which the nuclear force of attraction is very large as compared to the electrostatic force of repulsion. Since the nuclear force of attraction is much greater than the electrostatic force of repulsion, so a small nucleus is very stable.