Inside the nucleus there is a competition between two opposing forces:

  • The proton has a positive electric charge so it feels the electrostatic force. Each proton is trying to repel all the others.
  • Both types of nucleon feel the strong nuclear force, which is attractive at this distance.

At this scale, the attraction caused by the strong force is greater than the electrostatic repulsion between protons. This means the nucleus is held together.

The strong force has a very short range, so larger nuclei are not as strongly bound. This leads to an unstable nucleus that can undergo radioactive decay or nuclear fission.

Image showing a nucleus with arrows indicating the strong nuclear attraction (blue) and electrostatic repulsion (red)

Figure 1. A nucleus showing the strong nuclear attraction (blue) and electrostatic repulsion (red).