calculating the binding energy per nucleon for caesium atom

To find the binding energy of copper, copper has two isotopes , copper-62 and copper-64,

 for ⁶²Cu, we start by finding the actual mass which can be calculated as follows

it has 29 protons and 33 protons,

29 x 1.007825 + 34 x 1.008665 = 63.5

  the measured mass is 62.929601

 therefore mass defects is 0.600000amu

 therefore  the binding energy is given as

0.6 x ( 3 x10⁸)² =5.327406 x10¹⁰  Joules

binding energy per nucleon is therefore =8.4562 x 10¹⁴Joules.

 For ⁶⁵Cu, the binding energy

29 x 1.007825 + 36 x 1.008665 = 65.5

the measured mass is given by 64.927794

the mass defect is therefore

 65.5 - 64.927794 =0.6amu

 the binding energy is therefore

0.6 x ( 3 x10⁸)² =5.327406 x10¹⁶  Joules

and binding energy per nucleon is therefore =8.4562 x 10¹⁴Joules.

the mass 0.6 amu is was is what is converted  to energy to hold the nucleus.