Atoms can be classified as stable or unstable. Unstable atoms have excess energy in their nuclei. ARADIOACTIVE MATERIAL contains atoms which are unstable and attempt to become more stableby ejecting particles, electromagnetic energy (photons), or both. When a radioactive atom ejectsparticles and/or photons, the atom undergoes a process called DISINTEGRATION (or decay). RADIATION is the term given to the particles and/or energy emitted by radioactive material as itdisintegrates.One curie is defined as that amount of any radioactivematerial that will decay at a rate of 37 billion disintegrations per second (based upon the disintegrationrate of 1 gram of radium-226).Radiation emitted by radioactive material can produce IONIZATIONS and, therefore, is calledIONIZING RADIATION. Ionization is the process of stripping, knocking off, or otherwise removingelectrons from their orbital paths, creating free electrons and leaving charged nuclei.