Which statement best describes a beta particle?

• A. Positively charged helium nucleus
• B. Electron ejected from the nucleus
• C. Gamma ray photon
• D. Neutrino

Answer: (B)

A beta particle is a fast-moving electron emitted from the nucleus during beta decay. In beta minus decay, a neutron converts into a proton, an electron, and an antineutrino, and the electron is ejected from the nucleus to conserve charge and energy. This makes the defining feature of a beta particle its negative charge and its identity as an electron.

The other options describe different forms of radiation: an alpha particle is a positively charged helium nucleus, a gamma ray is electromagnetic radiation (a photon) with no mass, and a neutrino is a nearly massless neutral particle that can be emitted in some decays but is not the beta particle itself.