1. The problem statement, all variables and given/known data Find the energy released for the reactions in the Proton-Proton chain. 2. Relevant equations Proton-Proton Chain: 1H + 1H -> 2H + e+ + v e+ + e- -> γ + γ 2H + 1H -> 3He + γ 3He + 3He -> 4He + 2 1H 3. The attempt at a solution To find the energy released in each of these reactions, I am calculating the mass deficit. For the first reaction, I am finding a mass deficit of 2(1.007825 u) - 2.014102 u - 0.0005486 = 0.0009994 u because v (neutrino) is massless. Then the energy in MeV of this reaction is 0.0009994 u x 931.5 MeV/u = 0.9309411 MeV. However, I checked http://en.wikipedia.org/wiki/Proton–proton_chain_reaction#The_proton.E2.80.93proton_chain_reaction, and it looks like the energy released is 0.42 MeV. Did I do the calculation correctly? Thank you for any help!