[I know this thread is a mix of 6-year-old and month-old messages, but I just spotted it....]

There is a reasonably straightforward explanation for the shape of the nuclear binding energy curve. The Bethe-Weizsäcker mass formula accounts for most of the contributions to atomic mass. However, it does not account for "shell" effects, i.e. the existence of magic numbers that create islands of stability in the chart of the nuclides.... See

http://en.wikipedia.org/wiki/Semi-em...l_mass_formula

BBB