Binding Energy

Why both fission and fusion release energy

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A nucleus weighs less than its separate parts. The difference is the binding energy (E = Δm c²).
• Binding energy per nucleon peaks near iron and nickel; the liquid-drop model explains why.
• Fusing light nuclei, or splitting heavy ones, moves toward iron and releases energy.

Steps

1. Missing mass
2. Weighing helium
3. The curve of binding energy
4. The valley of stability
5. The binding of iron
6. The end of a star