(ii) The constancy of the binding energy in the range 30 < A < 170 is a
consequence of the fact that the nuclear force is short-ranged Consider
a particular nucleon inside a sufficiently large nucleus It will be under
the influence of only some of its neighbours, which come within the
range of the nuclear force If any other nucleon is at a distance more
than the range of the nuclear force from the particular nucleon it will
have no influence on the binding energy of the nucleon under
consideration