Answer
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.