📈 Binding energy per nucleon — a peak at iron that powers stars and reactors

Plot the binding energy per nucleon B/A against mass number A and a single curve appears: it climbs steeply for light nuclei, peaks near iron (A≈56, ≈8.75 MeV), then falls slowly for heavy nuclei. Anything that moves a nucleus toward that peak releases energy.

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The curve B/A vs A: light nuclei bind weakly, the value peaks near iron (A≈56, ≈8.75 MeV), then falls slowly for the heaviest nuclei. Drag A to read B/A at any nucleus.

Mass number A 56

B_E/A = [Z m_p + (A−Z)m_n − M]c² / A = — MeV
A = — · peak ≈ 8.75 MeV at A≈56 (iron) · fusion below, fission above — both release energy

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