What type of radiation consists of high-energy electrons with essentially no mass?

Beta radiation consists of high-energy electrons that are emitted from the nucleus of an atom during radioactive decay. These electrons have very little mass compared to other particles like protons and neutrons, making them nearly massless in terms of their impact on nuclear reactions. This type of radiation occurs when a neutron in an unstable nucleus is converted into a proton, resulting in the emission of an electron.

In contrast, alpha radiation involves the emission of alpha particles, which consist of two protons and two neutrons, making them significantly more massive. Gamma radiation consists of high-energy photons, which are massless but does not include particles like electrons. Neutron radiation comprises free neutrons, which also have a considerable mass associated with them. Thus, beta radiation is characterized by the emission of high-energy, nearly massless electrons, distinguishing it from the other types of radiation listed.