Nuclides with the same number of protons but with different numbers of neutrons are called isotopes. Radioactive nuclides can generally be described as those which have an excess or deficiency of neutrons in the nucleus. The radiation emitted can be particulate or electromagnetic or both. The various types of radiation and examples of decay are shown below. Beta particles are emitted from the nucleus and have a mass equal to that of electrons.
Betas can have either a negative charge or a positive charge.
Negatively charged betas are equivalent to electrons and are emitted during the decay of neutron rich nuclides. Gammas are emitted during energy level transitions in the nucleus. They may also be emitted during other modes of decay. In certain neutron deficient nuclides, the nucleus will capture an orbital electron resulting in conversion of a proton into a neutron. This type of decay also involves gamma emission as well as x-ray emission as other electrons fall into the orbital vacated by the captured electrons.