Isotope
Some elements only have a single isotope that is stable. For example, fluorine-19 (19F) is the only stable isotope of fluorine. The other isotopes of fluorine decay rapidly so they are not found in nature. Other elements have many stable isotopes. For example, xenon has seven stable isotopes. It also has two isotopes that decay very slowly that are found in nature. The largest number of stable isotopes for any element is ten, for the element tin. Some elements do not have any stable isotopes, such as curium. These only exist on Earth because they are created in nuclear reactors, nuclear explosions, or particle accelerators.