For the same reason, larger nuclei (more than about eight nucleons in diameter) are less tightly bound per unit mass than are smaller nuclei; breaking a large nucleus into two or more intermediate-sized nuclei releases energy.
Af samme årsag er tungere kerner (mere end 8 kernepartikler i diameter) mindre fast bundet pr. masseenhed end mindre kerner; når en tung kerne brydes op i to eller flere med medium-masse frigøres energi.