See explanation below.
Work Step by Step
Find the mass of the actual particles and subtract from the mass of the isotope. That difference is the mass defect, which will be equivalent to the bonding energy according to E = mc^2. Divide the energy by the number of nucleons (protons and neutrons) and you've got the binding energy per nucleon. Mass of particles in I-131 nucleus 53 protons x 1.0073 amu/proton = 53.3869 amu 78 neutrons x 1.0087 amu/neutron = 78.6786 amu Total mass of particles = 132.0655 Mass defect = 132.0655 - 130.9061 = 1.1594 amu Convert to kilograms, and get 1.9252 × 10^-27 kilograms E = mc^2 = 1.9252 × 10^-27 kg x (3.00x10^8 m/s)^2 = 1.7327 x 10^-10 J Binding energy per nucleon = 1.7327 x 10^-10 J / 131 = 1.3227 x 10^-12 J/nucleon or 8.2553 MeV per nucleon.