Beta Decay

Beta decay is a type of nuclear decay in which one or more beta particles are emitted. A beta particle is an electron or a positron.

There are several subtypes of beta decay. These are listed in the table below.

Single Beta-Minus Decay	A decay process in which a neutron changes into a proton, and an electron is emitted.
Single Beta-Plus Decay	A decay process in which a proton changes into a neutron, and a positron is emitted.
Double Beta-Minus Decay	A decay process in which two neutrons change into two protons, and two electrons are emitted. A very rare process.
Double Beta-Plus Decay	A decay process in which two protons change into two neutrons, and two positrons are emitted. A very rare process.

While the term ‘beta decay’ can refer to any of these four processes, often the term is used just to mean the first one: single beta-minus decay.

Beta decay is named after the second letter of the Greek alphabet, β. The symbol for a beta particle is β – \(\beta^{-}\) for an electron, which has a negative electric charge, and \(\beta^{+}\) for a positron, which has a positive electric charge. Beta particles are also called beta rays and beta radiation.

An Example of Beta-Minus Decay

Phosphorus-32 is an isotope of phosphorus that decays via beta-minus decay to sulfur-32. The nuclear equation below represents this process.

A neutron in the nucleus of the phosphorus atom changes into a proton, releasing an electron and an electron antineutrino as it does so. Since the number of protons increases by one, the atomic number of the nucleus increases by 1, but since the nucleus loses one neutron while gaining one proton, the total number of nucleons doesn't change, and its mass number stays the same.