Nucleus Builder
Build a nucleus from protons and neutrons. Find its mass defect and binding energy, and see where it sits on the binding energy curve.
Your task: use the two masses above to find the mass defect, then use 1 u = 931.5 MeV/c2 to find the binding energy. Divide by the number of nucleons to compare nuclei.
Show the working for this nucleus
The nucleons in a nucleus have less mass than the same nucleons apart. The missing mass, the mass defect Δm, has been released as energy as the nucleus formed: E = Δm c2. The same amount of energy must be supplied to pull the nucleus apart again.
Binding energy per nucleon is a measure of stability. Light nuclei release energy when they fuse. Heavy nuclei release energy when they split (fission). Both processes move towards the peak near iron-56 and nickel-62.
The masses are for the nucleus, without electrons. If you are given an atomic mass instead, take away the mass of the electrons first (Z × 0.000549 u), or you will be out by about 3 MeV for carbon.
For 15 common nuclei the binding energy is the measured value. For every other combination it is estimated with the semi-empirical mass formula, which is good to within a few MeV and less accurate for the lightest nuclei. A hollow marker on the graph means an estimate. The dots on the graph are measured values.
Learn more in the Binding energy lesson. Original idea by Aaron (Scots College), rebuilt in the Physics High style.