How would you figure out a beta decay for atomic number??

Question

A monoatomic atom or ion with 72 protons, 72 neutrons, and 78 electrons undergoes a beta decay. What is its atomic number after the beta decay?

Answer 1

In beta decay (actually beta minus decay), a neutron turns into a proton, an electron and an antineutrino. So, what was once 72 neutrons is now 71 neutrons. And what was 72 protons, is now 73 protons. The electron however, would typically have to much energy to be recaptured by the atom so it would be lost making the electron number stay the same at 78.

So, since atomic number is neutrons + protons, it is 71 + 73 which is 144 (notice it's still the same because it used to be 72 + 72 = 144)