Not all isotopes of a given element are stable. For example, tin has twenty-two different known isotopes, ten of which are stable and twelve of which are unstable (though there is some debate about just how stable those ten are). Stable is, of course, a relative term. Usually when one says an isotope of an element is stable, it means that it has a decay half-life that is too long to be measured by current methods. There are some elements, such as technetium, radon, and plutonium that do not have any stable known isotopes. In fact, no elements with an atomic number of over 83 (i.e., more than eighty-three protons) have any known isotopes that are considered to be stable!