The binding-energy-per-nucleon curve for nuclei first rises sharply, reaches a broad maximum around mass number 56, and then falls slowly for heavier nuclei.
(i) Describe qualitatively how this variation explains the release of energy when very heavy nuclei such as 235U undergo fission into medium-mass fragments.
(ii) Explain, using the same curve, why energy is also released when very light nuclei such as the isotopes of hydrogen combine to form a heavier nucleus.
(iii) State the approximate mass-number ranges of the parent nuclei that are most suitable for (a) fission and (b) fusion reactions, giving reasons in each case.