- Electron emitted from the nucleus when a neutron decays to a proton and an electron.
- A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Large amounts of beta radiation may cause skin bums, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of metal or plastic.
Source: U.S. Nuclear Regulatory Commission