239
11. (a) For Pu, Q =94e and R =6.64 fm. Including a conversion factor for J eV, we obtain

3Q2 3[94(1.60 × 10-19 C)]2(8.99 × 109 N·m2/C2) 1eV
U = =
20Ä„µ0r 5(6.64 × 10-15 m) 1.60 × 10-19 J
= 1.15 × 109 eV = 1.15 GeV .
(b) Since Z =94 and A = 239, the electrostatic potential per nucleon is 1.15 GeV/239 = 4.81 MeV/nucleon,
and per proton is 1.15 GeV/94 = 12.2MeV/proton. These are of the same order of magnitude as
the binding energy per nucleon.
(c) The binding energy is significantly reduced by the electrostatic repulsion among the protons.