Within the nucleus, there are diﬀerent forces that act between the particles. The strong nuclear force is the force between two or more nucleons. This force binds protons and neutrons together inside the nucleus, and it is most powerful when the nucleus is small and the nucleons are close together. The electromagnetic force causes the repulsion between like-charged protons. These two forces produce opposite eﬀects in the nucleus. The strong nuclear force acts to hold all the protons and neutrons close together, while the electromagnetic force acts to push protons further apart.
In atoms with small nuclei, the strong nuclear force overpowers the electromagnetic force. As the nucleus gets bigger, the electromagnetic force becomes greater than the strong nuclear force. In these nuclei, it’s possible for particles and energy to be ejected from the nucleus. These nuclei are called unstable, and this instability can result in radiation and fission.