Chemistry / Unit 12 Chem 2503 worked example, 60 to 90 seconds
Calculating Binding Energy per Nucleon
The idea
Calculating binding energy per nucleon means finding a nuclide's mass defect from the difference between its separate-particle mass and its measured mass, converting that mass defect to energy using the mass-energy equivalence relationship, and dividing by the total number of nucleons.
In practice
For iron-56, comparing the summed mass of 26 protons, 30 neutrons, and 26 electrons against the nuclide's measured mass of 55.9349 amu gives a mass defect that converts to a binding energy near 492 MeV total, or about 8.8 MeV per nucleon once divided across all 56 nucleons.
Where people slip
Comparing a bare-nucleon sum (protons and neutrons only) against the atomic, electron-inclusive measured mass mismatches the two sides — the summed side must include electrons too, as the iron-56 example does — and reporting total binding energy where per-nucleon was asked reverses stability comparisons between nuclides.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for Chemistry