Fission: Some heavy nuclei decay by splitting into 2 or 3 fragments plus some neutrons. These fragments form new nuclei which are usually radioactive;
Alpha Decay: Two protons and two neutrons leave the nucleus together in an assembly known as an alpha-particle;
An alpha-particle is a He-4 nucleus;
Beta Decay - Electron Emission: Certain nuclei with an excess of neutrons may reach stability by converting a neutron into a proton with the emission of a beta-minus particle;
A beta-minus particle is an electron;
Beta Decay - Positron Emission: When the number of protons in a nucleus is in excess, the nucleus may reach stability by converting a proton into a neutron with the emission of a beta-plus particle;
A beta-plus particle is a positron;
Positrons annihilate with electrons to produce two back-to-back gamma-rays;
Beta Decay - Electron Capture: An inner orbital electron is attracted into the nucleus where it combines with a proton to form a neutron;
Electron capture is also known as K-capture;
Following electron capture, the excited nucleus may give off some gamma-rays. In addition, as the vacant electron site is filled, an X-ray is emitted;
Gamma Decay - Isomeric Transition: A nucleus in an excited state may reach its ground state by the emission of a gamma-ray;
A gamma-ray is an electromagnetic photon of high energy;
Gamma Decay - Internal Conversion: the excitation energy of an excited nucleus is given to an atomic electron.
