In beta decay, which process occurs?

• A. An electron is emitted from the nucleus.
• B. A proton changes into a neutron with the emission of a positron.
• C. A neutron changes into a proton with the emission of an electron.
• D. Gamma rays are emitted without changing the nucleus.

Answer: (C)

Beta decay is a process in which the nucleus changes its composition via the weak interaction, converting one nucleon into the other while emitting a light particle. In the common beta-minus decay, a neutron becomes a proton and emits an electron (and an antineutrino). This specific transformation is the essence of beta decay and explains why the nucleus gains one proton while losing one neutron, increasing the atomic number by one.

Gamma decay, by contrast, releases gamma rays without changing the numbers of protons or neutrons, so it isn’t beta decay. There’s also beta-plus decay, where a proton becomes a neutron and emits a positron (and a neutrino). The process described—neutron turning into a proton with the emission of an electron—captures the typical beta-minus decay pathway.