I was curious as to the difference in free neutron decay and the lack of decay when bound in a nucleus. I found the following statement here http://en.m.wikipedia.org/wiki/Neutron#Free_neutron_decay I don't understand that. Is the wave function of the neutron different when free or bound? The phrase "is balanced" sounds wrong; balanced by who or what? Perhaps they mean that instead of a Feynman diagram with a neutron in and proton/electron/anti neutrino out, we should use a diagram with a nucleus in and a nucleus(with higher atomic number)/electron/anti neutrino out. That would suggest to me the wave function of the nucleus supersedes the wave functions of the constituent nucleons. Would someone please explain those two Wikipedia sentences, or point me to a more understandable source? Follow up question: Since the binding energy per nucleon is different in different elements, is the stability of a bound neutron a function of which element/isotope it is bound in?