This is just a simple conceptual question. When we try to calculate a nuclear binding energy of some nucleus, we get the mass defect(del M) and find the binding energy by using (del M)c^2 right? Well, what I do not understand is this. For instance, let's take a formation of a flourine-19. Flourine formation(out of neutrons and protons) would be exothermic because del M is negative, but why would energy be released to the surrounding if also the same amount of energy is being used to bind the nucleus together? Meaning, if some (x)J amount of energy is being used as a binding energy of flourine, the mass would convert to that energy and will be thus used to bind the flourine nucleus (and if that energy is being hold onto by the nucleus as a binding energy, it should not be released to the surrounding. no?) I hope I have phrased my question right. Thank you.