So my question has a few parts to it. First, if an atom is decaying and the proton (Z) number is decreasing in the decay process, am I correct in assuming that the nucleus is either decaying by electron capture of beta plus emission? Secondly, I understand that beta plus emission can only occur is the mass of the original atom is at least 2 electron masses larger than the final atom. Therefore if the final mass is under 2 electron masses, the atom decays by electron capture. However, if the final mass is larger than 2 electron masses, how do you know if it is decaying by beta plus emission or electron capture? Thanks in advance for any help. Emily.