Difference Between Alpha, Beta And Gamma Emissions
Soon after Marie Curie coined the word radioactivity, the British scientists Ernest Rutherford and Frederick Soddy explained its nature by describing what went on inside the nucleus of an unstable atom, or radionuclide. Such nuclei undergo small disintegrations called radioactive decay. In the process, tiny, high-speed particles and rays fly from the nucleus in every direction. Nuclear chemists found they could study these particles and rays by separating them into different streams using electrical or magnetic fields.
Specifically, scientists found three distinct types of nuclear radiation, which they dubbed alpha, beta, and gamma rays after the first three letters in the Greek alphabet. All naturally occurring radionuclides emit one or more of these three kinds of radiation.
Alpha radiation consists of positively charged particles that carry a charge of +2 and an atomic mass of 4. Nuclear chemists think of these particles as helium nuclei, for each alpha particle is a tiny cluster of two protons and two neutrons—identical to the nucleus of an ordinary helium atom. Alpha particles move at speeds between 2,000 and 20,000 miles per second, or 1 to 10 percent of the speed of light.
Beta radiation consists of negatively charged particles. In essence, it is a stream of electrons. How can a nucleus—a collection of protons and neutrons—produce electrons? We now know that beta particles result from the transformation of a neutron (charge 0) into a proton (charge +1) and an electron (charge −1). The new proton remains in the nucleus of the radioactive atom. The electron is ejected at nearly the speed of light.
Gamma radiation consists of high-energy photons, or radiant energy. It can be compared to X rays or intense light waves with very short wavelengths. With neither mass nor electrical charge, gamma rays travel at the speed of light.