Binding Energy per Nucleon (Fusion vs Fission)
Trace the curve that explains where nuclear energy comes from — see why fusing light nuclei and splitting heavy ones both release energy, and check the energy of a specific reaction against the curve.
Preview — sign up free to change the numbers yourself
What you can adjust
- Reaction
- 0 – 3
- Highlight mass number (A)
- 1 – 240
- Show measured reference points
- 0 – 1
Pick a reaction to check against the curve — fusing light nuclei (D+T), splitting a heavy one (U-235 fission), running the carbon-forming triple-alpha process backwards, or 'reacting' iron-56 with itself (no energy gain — it already sits at the curve's peak).
Marks this mass number on the curve and reads off its binding energy per nucleon. Defaults to 56 (iron), right at the curve's peak.
Plot real measured binding energies (AME2020) as reference dots alongside the formula curve — useful since the formula is known to under/over-shoot for very light nuclei.
About this simulation
What it shows
A curve of binding energy per nucleon against mass number, with a marker for the nucleus you choose and a check of one nuclear reaction against the curve.
The key idea
Energy is released when nuclei move up the curve. Light nuclei gain by fusing and heavy nuclei gain by splitting, while iron-56 sits at the peak where neither direction releases energy.
Try this
Set Highlight mass number (A) to 56, then to 4 and to 235: iron sits at the peak, and both the light and the heavy nuclei sit lower on the curve.
The curve comes from a fitted formula that is least accurate for very light nuclei. Turn on Show measured reference points to compare it with measured values.