Beta Decay Definition

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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.

How Beta Decay Works

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 following reaction. Here X is the parent atom, Y is the daughter atom, Z is the atomic mass of X, and A is the atomic number of X:
ZXAZYA+1 + e- + antineutrino

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 following reaction, 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:
ZXAZYA-1 + e+ + neutrino

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

Practical Examples

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