When a $\beta ^ { - }$particle is emitted from an unstable nucleus, the atomic mass number of the nucleus

Question

Quizplus · Accepted Answer

When a $\beta^-$ particle (which is an electron) is emitted from a nucleus, the atomic mass number (which counts protons and neutrons) does not change because the mass of an electron is negligible compared to that of protons and neutrons. The emission involves a neutron in the nucleus transforming into a proton and an electron, where the electron is emitted as the $\beta^-$ particle. The number of protons increases by 1, but the overall atomic mass number remains the same because it's the sum of protons and neutrons.

When A β−\beta ^ { - }β− Particle Is Emitted from an Unstable Nucleus, the Atomic Mass

When A $\beta ^ { - }$ Particle Is Emitted from an Unstable Nucleus, the Atomic Mass