When electromagnetic radiation is ionizing, it breaks the atomic bond and creates ions, which are atoms and molecules with fewer electrons or a greater number of electrons than they normally have. Examples are gamma rays, x-rays, CAT scans and ultraviolet light.
In contrast, non-ionizing radiation does not have enough energy to alter the electron structure; however, it may be harmful depending on the amount of exposure. See
ion and
electromagnetic hypersensitivity.