Question

How much energy is required to make a Iron atom from hydrogen atoms

Answer 1

If you know the mass of a nuclide, the energy released in its formation from Z protons (A-Z), neutron and Z electrons is given by the difference  Z(me  +mp ) + (A-Z) mn - mnuclide multipied by c2.

for example

m(U -238) = 238.05078826 u = 1,66054 × 10−24  x 238.05078826 = 3.9529 10-22 g

mp=1.6726219 × 10-24 g  me =9.10938 ×10−28g  mn = 1.674927×10−24 g

Z(me +mp ) + (A-Z) mn = 3.9850436 x 10-22g

Difference = 3.2143631 x 10-24 g = 3.2143631 x 10-27 kg

Energy released= difference x c 2 = 2.8889255 10-10 J