Free and bound energy budgets close per nucleon. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Four nucleons bind at two each
Free total 20 joules minus nucleus budget 12 joules gives binding 8 joules across 4 nucleons.
8÷4=2
Six nucleons bind at three each
Free total 30 joules minus nucleus budget 12 joules gives binding 18 joules across 6 nucleons.
18÷6=3
Eight nucleons return to two each
Free total 40 joules minus nucleus budget 24 joules gives binding 16 joules across 8 nucleons.