TYPES OF RADIATIONS

Elements are made up of atoms. An atom has a nucleus as we have seen previously. Some elements have atoms that are so big that they are very unstable so they undergo decay, that is they disintegrate. There are basically, three types of radiations, namely:

• Alpha radiation
• Beta radiation
• Gamma radiation

1. What is an Alpha Radiation?
   Alpha radiation is a stream of positively charged particles, called alpha particles. It has an atomic mass of 4 and a charge of +2. It is, therefore a helium nucleus (42He ). The superscript is the atomic mass and the subscript is the atomic number. When a nucleus emits an alpha particle, the mass number of the nucleus decreases by four units and the atomic number decreases by two units. For example: When uranium (3892U) emits an alpha radiation, it produces the element Thorium (23490Th). 
   23892U → 42He + 23490Th
2. What is a Beta Radiation?
   Beta radiation is a stream of electrons, called beta particles. Beta particle emission occurs when the ratio of neutrons to protons in the nucleus is too high. In this case, an excess neutron transforms into a proton and an electron. The proton stays in the nucleus and the electron is ejected energetically. This process decreases the number of neutrons by one and increases the number of protons by one. Since the number of protons in the nucleus of an atom determines the element, the conversion of a neutron to a proton actually changes the radionuclide to a different element. For example, when Thorium emits a beta particle, it forms the element, Palladium (23491Pa).
   23490 Th→  + 23491Pa
   As you can see, the mass of the nucleus is unchanged, but the atomic number has increased by one unit. 
3. What is a Gamma Radiation? Gamma rays are high-energy photons with a very short wavelength (0.0005 to 0.1 nm). When an energy change occurs within the atomic nucleus, a gamma radiation occurs. Neither the atomic number or mass changes when Gamma emission occurs. Alpha and beta emission are often accompanied by gamma emission, as an excited nucleus drops to a lower and more stable energy state. For example, Cesium-137 undergoes radioactive decay by gamma radiation, a neutron transforms to a proton and a beta particle. The additional proton changes the atom to barium-137. The nucleus ejects the beta particle, however, the nucleus still has too much energy and ejects a gamma photon (gamma radiation) to become more stable.
4. Positron is a particle with the same mass as an electron, but a charge of +1 instead of -1. This emission isn't observed in natural radioactivity, but it is a common mode of decay in induced radioactivity. Induced radioactivity is done in the chemical lab using bombardment reactions to produce very heavy elements, including many which don't occur in nature.