- a radioactive process in which a beta particle is emitted from the nucleus of an atom, raising the atomic number of the atom by one if the particle is negatively charged, lowering it by one if positively charged.
- the radioactive transformation of an atomic nucleus accompanying the emission of an electron. It involves unit change of atomic number but none in mass numberAlso called: beta transformation, beta process
- A form of radioactive decay caused by the weak nuclear force, in which a beta particle (electron or positron) is emitted.♦ In beta-minus decay, a neutron in an atomic nucleus decays into a proton, an electron, and an antineutrino. The electron and antineutrino are emitted from the nucleus, while the proton remains. The atomic number of the atom is thereby increased by 1. The decay of Carbon-14 into Nitrogen-14, a phenomenon useful in carbon dating, is an example of beta-minus decay.♦ In beta-plus decay, a proton in an atomic nucleus decays into a neutron, a positron, and a neutrino. The positron and neutrino are emitted from the nucleus, while the neutron remains. The atomic number of the atom is thereby reduced by 1. The decay of Carbon-10 to Boron-10 is an example of beta-plus decay. See also W boson.