Beta Particle
Definition
A fast electron (or positron) shot out of a decaying nucleus: more penetrating than alpha, stopped by plastic or a few millimeters of metal.
Symbol: ·
Technical definition
A beta particle is a high-energy electron or positron emitted when a neutron converts to a proton (or vice versa) in the nucleus. Beta-minus emission increases the atomic number by 1, and beta particles penetrate further than alpha but ionize less densely.
Example
Carbon-14 becomes nitrogen-14 by beta-minus decay: a neutron becomes a proton, spitting out an electron.
Common confusion
Beta electrons do not come from the atom's electron shells. They are created in the nucleus at the moment of decay, which is why beta decay changes the element.