The semi-empirical mass formula (Bethe-Weizsäcker) models nuclear binding energy using volume, surface, Coulomb, and asymmetry terms. The valley of stability Z(A) is used to estimate the proton number for each mass number.
Key Concepts
• Fe-56 has the highest BE/A (~8.8 MeV) — the most stable nucleus
• Fusion: light nuclei combine to move right on the curve, releasing energy
• Fission: heavy nuclei split to move left on the curve, releasing energy
• Both processes release energy because they move toward the Fe-56 peak
• The binding energy deficit = mass defect × c² (Einstein's E = mc²)