the binding energy of an atomic nucleus can be calculated by finding the "mass defect"

 this is the "missing mass" __  so called because the sum of the masses of the protons and neutrons is greater than the mass of the nucleus

this "missing mass" has been converted onto the binding energy of the neucleus
__ and can be calculated using Einstein's famous E=mc^2

the mass of a beryllium-9 atom is 9.012182amu __ 4 protons, 5 neutrons, and 4 electrons

 proton mass is 1.007276 amu ,  neutron mass is 1.008665 amu, and  electron mass is 5.486×10−4 amu (amu is atomic mass units; 1.6606x10^-27 kg)

component masses __ 4p + 5n + 9e = 9.077366 amu

mass defect __ 9.077366-9.012182= 0.065184 amu 

0.065184 amu x 1.6606x10^-27 kg/1 amu=1.082446x10^-28 Kg

E=mc²=(1.082446x10^-28 Kg)*(3.0x10^8 m/s)²=9.742014x10^-12 J or 60.8048 Mev