At the center of an atom, there is a nucleus that is made up of neutrons and protons.

A neutron has no net charge. It acts like a ‘glue’ that keeps the nucleus together. This force that holds a nucleus together is called attractive strong forces.

A proton has a net positive charge. A proton exerts repulsive Coulombic forces towards other protons since like charges repel.

An atom is considered stable when it does not spontaneously emit radiation. In other words, the attractive strong forces overcome the repulsive forces and is able to hold the nucleus together.