The Binding-Energy Curve
Total binding energy usually increases when a nucleus contains more nucleons. To compare how tightly different nuclei are bound, divide by the nucleon number and compare binding energy per nucleon.
Higher on the curve means more tightly bound
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Divide the total binding energy by the nucleon number .
- The curve rises steeply for light nuclei.
- It reaches a maximum near iron-56.
- It then decreases slowly for very heavy nuclei.
- A larger binding energy per nucleon means that, on average, more energy is required to remove each nucleon. The nucleus is more tightly bound and more stable.
Which is more tightly bound per nucleon: a nucleus at 7.6 MeV per nucleon or one at 8.5 MeV per nucleon?
Show worked answer
The nucleus at 8.5 MeV per nucleon is more tightly bound because more energy is required per nucleon to separate it.
On paper, sketch binding energy per nucleon against nucleon number from 1 to 250. What three features must your curve show? [2]
Show worked answer
Show a steep rise for light nuclei, a maximum near nucleon number 56 and a slow decrease for heavy nuclei. The right-hand end stays well above zero.