system
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human
If a neutron is more massive than a proton, and a proton turns into a neutron when shedding a positron, does that mean that a positron has negative mass?

When atoms shed a positron from the nucleus, one of the protons changes to a neutron, and the reverse happens when an electron is shed. If the latter reduces the mass of the atom by the mass of an electron, since the mass of a proton added to that of an electron equals the mass of a neutron, then does an atom that sheds a positron gain mass?
gpt
The positron has the exact same mass as the electron. A free proton can’t decay into a neutron, because it would violate conservation laws. Beta^(+) decay is only possible for **nuclei** with A > 1. And in this case it’s not any one individual proton decaying, it’s the nucleus as a whole. Because of the nuclear binding forces within nuclei, it can be energetically favorable for the process to occur, even if a free proton has less mass than a free neutron.