What is the primary force that holds the nucleus of an atom together?

The primary force that holds the nucleus of an atom together is the strong nuclear force. This fundamental force acts between protons and neutrons, which are collectively known as nucleons. The strong nuclear force is incredibly powerful, overcoming the electromagnetic repulsion that exists between positively charged protons. It is effective only at very short ranges, on the order of one femtometer (10^-15 meters), which is the approximate size of an atomic nucleus.

This force ensures that nucleons can remain tightly packed within the nucleus despite the repulsive electromagnetic forces between protons. Unlike gravitational force, which is significantly weaker and has a negligible effect at the atomic scale, or the weak nuclear force, which is responsible for certain types of radioactive decay but does not contribute to holding the nucleus together, the strong nuclear force is essential for the stability of atomic nuclei. Thus, the strong nuclear force is critical for the existence of atoms as we know them.