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

..................................................................................

Beta Decay Definition

by Anne Marie Helmenstine, Ph.D. 

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 reaction:

^ZX_A → ^ZY_A+1 + e^- + antineutrino

Here 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:

^ZX_A → ^ZY_A-1 + e⁺ + neutrino

Here 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.

Practical Examples

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

Anne Marie Helmenstine, Ph.D.

·   Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

·   Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

·   ThoughtCo and About Education chemistry expert since 2001.

·   Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/beta-decay-definition-608733