Over 3500 isotopes are known, and most are merely laboratory curiosities. In some cases more than one form of an isotope can exist. These different forms of the isotope have the same number of protons and neutrons but different half-lives. They are different because the protons and neutrons can arrange themselves in different ways. There is an isomer of 60Co with a half-life of 10 minutes.
Isotopes try to decay to more stable isotopes.
Beta decay also emits a nearly invisible neutrino. Other isotopes decay by alpha decay , emitting an alpha particle which is really a 4He nucleus. Heavy elements occasionally decay by spontaneous fission , dividing in half. An isotope can decay in several possible ways often emitting gamma-rays as loses energy. Now go back to the Periodic Table of Isotopes and click on some of the elements to see their isotopes.