E.3.16 (HL)—Binding energy above A≈60

Read the heavy-nucleus trend

Above approximately $A\approx60$ , binding energy per nucleon is broadly similar but slowly decreases as nucleon number increases. The increasing proton repulsion makes very heavy nuclei less tightly bound per nucleon.

Use the approximation carefully

“Approximately constant” does not mean identical for every nuclide. Use the trend to compare regions and to explain why fission of very heavy nuclei can release energy.

Common trap

Do not turn the broad plateau into a new maximum at large A. The main maximum is in the medium-mass region, followed by a gradual decline.

Retrieve the HL evidence

Nuclear stability, scattering deviations, the N–Z stability band and discrete alpha/gamma spectra reveal the strong interaction and quantized nuclear levels.

Retrieve the decay equations

Use $N=N_0e^{-\lambda t}$ , $A=\lambda N$ , and $T_{1/2}=\ln2/\lambda$ . The continuous beta spectrum is explained by neutrino energy sharing.

E.3.16 (HL)—Binding energy above A≈60

Read Binding Energy Above A≈60

Retrieve the HL Nuclear Model