Massive stars are believed to generate energy through a sequence of fusion reactions that proceed until the core is largely composed of iron-56.
a. (a) Using the qualitative features of the binding-energy-per-nucleon curve, predict whether the fusion of carbon-12 nuclei into magnesium-24 would release or absorb energy.
b. (b) Explain clearly why further fusion reactions in the stellar core become energetically unfavourable once iron-56 is produced.
c. (c) Very heavy nuclei such as thorium and uranium sometimes undergo spontaneous α-decay. Use the binding-energy-per-nucleon curve to justify this observation qualitatively.