Beta particles are produced by which of the following processes?

• A. Conversion of a proton to a neutron or conversion of a neutron to a proton
• B. Emission of an alpha particle
• C. Spontaneous fission
• D. Electron capture

Answer: (A)

Beta decay involves a change between protons and neutrons inside the nucleus. When a neutron turns into a proton, an electron (the beta particle) and an antineutrino are emitted. When a proton turns into a neutron, a positron and a neutrino are emitted. So the beta particle originates from this nucleon-type transformation inside the nucleus. Other processes don’t produce beta particles: alpha decay ejects a helium nucleus, spontaneous fission splits the nucleus into lighter fragments, and electron capture converts a proton to a neutron while emitting a neutrino (and often X-rays from the atomic shell) rather than a beta particle.