Why is the binding energy constant between 30 and 170?

Explanation:

1. The nuclear force is the force that binds the protons and neutrons together in a nucleus. This force can exist between neutron-proton, proton-proton, and neutron-neutron.
2. It is a short-range force that is applicable up to a few fermimeters.
3. If the distance between nucleons is more than a few femtometers then this force will decrease and leads to zero.
4. For medium and large-size nuclei, the distance between nucleons will increase which leads to a decrease in the nuclear force. This will lead to a saturation in the nuclear force per nucleon for small and large size nuclei ( binding energy lies between 30 and 170).

These are the reasons why the binding energy is constant between 30 and 170.