The variation of binding energy per nucleon with mass number is an important indicator of nuclear stability.
(a) Draw a qualitative sketch of the binding energy per nucleon Ebn versus mass number A for stable nuclei. Mark the approximate mass number at which Ebn attains its maximum value.
(b) Using the sketch, explain why the fusion of two light nuclei such as 12H is an energy-releasing process.
(c) Using the same reasoning, explain why the fission of a heavy nucleus such as 92235U releases energy.
(d) State why nuclei having mass numbers close to A≈56 do not undergo spontaneous fission or fusion under ordinary conditions.