How does beta decay affect the nucleus?
Beta decay increases the number of protons in the nucleus, decreases the number of neutrons and leaves the mass essentially the same. ( the electron lost has an insignificant amount of mass)
A beta results in a neutron emitting a high energy electron and becoming a positive proton.
A classic examples is when radioactive Carbon 14 undergoes beta decay. One of the neutrons emits an electron or beta particle. That neutron now becomes a proton
Carbon 14 had 6 protons 8 neutrons and an atom mass of 14
after the radioactive beta decay the new atom is
Nitrogen 14 with 7 protons 7 neutrons and an atomic mass of 14
Beta decay changes the atomic number of the nucleus by increasing the number of protons, by decreasing the number of neutrons while leaving the atomic mass essentially the same.