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is this just a mass problem? and how do you "solve" this?

in beta minus decay a neutron turns into a proton and an electron (which is emmited) so final mass is (allways?) bigger or equal to original mass, since inside the nucleus mass stays the same, plus an electron added to the atom (which is not the emmited one, correct?). So it appears to me this is allways possible.

in beta plus a proton turns into a neutron plus an emmited positron, and so final mass is lower than orignal due to an electron loss to keep things balanced. so it appears to me that this is never possible(???)

what happens in EC? an electron is captured by the nucleus and a neutrino is emmited, why is the final atomic number lower?

so how do you figure out if any of this processes are possible for a given decay?

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  • $\begingroup$ beta-plus decay is certainly possible. Electron capture turns a proton in to a neutron, so Z has to decrease. Nuclear physics takes a bit of getting use to, but you will get there. $\endgroup$ – Jon Custer Jun 20 '17 at 14:46
  • $\begingroup$ Hum, for beta-plus; if i have for example an helium atom with only 1 neutron, and beta plus decay occurs, i get an hidrogen atom with 2 neutrons; so same atomic mass and minus one electron in the atom than before but one emmited positron; so mass stays the same, is this then possible? But wouldn't this mean its always possible then? Even if i had a stable helium atom and it beta plus decayed then mass in the nucleus of the hidrogen would be the same, and it has minus one electron in it but a positron emmited this is possible? $\endgroup$ – wrong1man Jun 20 '17 at 16:26
  • $\begingroup$ Well, look up the atomic masses and determine the mass deficit. This gives the Q value for the reaction. In your particular case, Tritium decays to He-3 by beta decay, not the other way around. He-3 is a stable isotope. $\endgroup$ – Jon Custer Jun 20 '17 at 16:29
  • $\begingroup$ But in the beta processes the mass inside the nucleus always stay the same correct? How do i then balance the masses of the emmited positrons/electrons by the beta decay and the emited/captured electrons to keep the atom electronically stable? $\endgroup$ – wrong1man Jun 20 '17 at 16:49
  • $\begingroup$ "so final mass is (allways?) bigger or equal to original mass" Uhm ... no it's not. Neutrons are more massive than protons. (There is also an anti-neutrino in the final state, but that doesn't really affect the mass balance.) And your line about beta-plus decay is also wrong. See physics.stackexchange.com/questions/318396/… amongst others. $\endgroup$ – dmckee Jun 20 '17 at 16:51

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