Alpha << AL fuh >> particle is an atomic nucleus that consists of two protons and two neutrons. An alpha particle can become the nucleus of a helium atom by capturing two electrons.
Two processes create alpha particles—(1) radioactive decay and (2) nuclear fusion. In the decay process, a larger nucleus emits (gives off) an alpha particle. For example, nuclei of heavy chemical elements, such as uranium and thorium, decay by emitting alpha particles. Almost all the helium on Earth is formed by radioactive decay.
In the fusion process, hydrogen atoms fuse (join) to create alpha particles. The amount of helium measured in stars and galaxies agrees with the big bang theory of the beginning of the universe. In that theory, most of the helium in the universe was produced by nuclear fusion within the first thousand seconds of the big bang.
Fusion also creates alpha particles inside stars. For example, a series of fusion reactions produces most of the sun’s energy. These reactions consume four protons and make one alpha particle; a single proton is the same as the nucleus of the simplest form of hydrogen. The alpha particle has less matter than the protons had. The missing matter is converted to energy.
