Now, the weak interaction is what's responsible for one of its neutrons, essentially for one of its quarks flipping and turning into a proton and I'm not going to detail of what a quark is, and all of that and the math can get pretty hairy but i want to give you an example of what a weak interaction does so if one of these neutrons turns into a proton we're going to have one extra proton but we're going to have the same number of nucleons instead of an extra neutron you have an extra proton here and now it is a different atom it is now barium and in that flipping, it will actually emit an electon and, an anti-electron neutrino 