Changes in atoms and in nuclei can generate and absorb radiation over a wide range of frequencies. The radiation can come from any part of the electromagnetic spectrum. The spectrum runs in order of increasing frequency from radio waves, microwaves and infrared, through visible light and ultraviolet, to X-rays and gamma rays.
Changes in the electrons of an atom emit or absorb radiation such as visible light and ultraviolet. Changes inside a nucleus, such as radioactive decay, emit gamma rays, which have the highest frequency of all the electromagnetic waves. Radio waves have the lowest frequency.
You can see one example with a black light lamp and tonic water. The tonic water absorbs ultraviolet radiation from the lamp and then emits visible light, so it glows. This effect is called fluorescence.