Nuclear Binding Energy

The energy holding a nucleus together — and the source of fusion's power.

Binding energy is what holds protons and neutrons together; the binding-energy-per-nucleon curve peaks near iron. Fusing light nuclei climbs toward that peak, releasing the difference as energy — the origin of fusion power.

The binding-energy-per-nucleon curve peaks near iron, so fusing light nuclei toward that peak releases energy while splitting heavy ones does the same from the other side. Fusion sits on the steep, low-mass part of the curve, which is why merging deuterium and tritium yields millions of times more energy per reaction than any chemical bond.