I'm in high school chem. and we are learning about nuclear chemistry (it's more of a physics topic in my opinion), but we learned that in beta decay a neutron loses mass (e- & anti-neutrino) and becomes a proton. We also learned that in positron emission a proton loses mass (positron & neutrino) and becomes a neutron. So, my question is...How is it that a neutron and proton can both become each other by losing mass?!? It's not balanced.