# Beta Decay Definition

Beta Decay Definition: Beta decay refers to the spontaneous radioactive decay where a beta particle is produced.

There are two types of beta decay where the beta particle is either an electron or a positron.

β- decay occurs when an electron is the beta particle. An atom will β- decay when a neutron in the nucleus converts to a proton by the reaction

ZXAZYA+1 + e- + antineutrino

where X is the parent atom, Y is the daughter atom, Z is the atomic mass of X, A is the atomic number of X.

β+ decay occurs when a positron is the beta particle. An atom will β+ decay when a proton in the nucleus converts into a neutron by the reaction

ZXAZYA-1 + e+ + neutrino

where X is the parent atom, Y is the daughter atom, Z is the atomic mass of X, A is the atomic number of X.

In both cases, the atomic mass of the atom remains constant but the elements are transmuted by one atomic number.

Examples: Cesium-137 decays to Barium-137 by β- decay.
Sodium-22 decays to Neon-22 by β+ decay.