The variation of binding energy per nucleon with mass number. Give the reason for the decrease of binding energy per nucleon for nuclei with high mass numbers.

For nuclei of high mass number, the number of protons inside the nucleus is more. These protons repel each other. Due to larger force of repulsion on account of greater number of protons present in the nucleus, the value of binding energy per nucleon decreases.
Class 12 Physics Chapter 13 Nuclei Session 2024-2025.