In a radioactive decay series similar to that shown in Figure 31.15, thorium  (atomic mass = 228.028 715 u) undergoes four successive a decays, producing a daughter nucleus.

Figure 31.15:

(a) Determine the symbol  for the nucleus produced by four successive a decays of 228 90 Th.

(b) What is the total amount of energy (in MeV) released in this series of a decays? The mass of the daughter nucleus can be obtained by using the result of part (a) and consulting Appendix F at the back of the book. The mass of a single a particle is 4.002 603 u.

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