Isotopes

An atom is missing a neutron or has an extra neutron. That type of atom is called an isotope. An atom is still the same element if it is missing an electron. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element.


Radioactive Isotopes
Radioactive isotopes, also called radioisotopes, are atoms with a different number of neutrons than a usual atom, with an unstable nucleus that decays, emitting alpha, beta and gamma rays until the isotope reaches stability. Once it's stable, the isotope becomes another element entirely. Radioactive decay is spontaneous so it's often hard to know when it will take place or what sort of rays it will emit during decay.'

references taken from: http://www.ehow.com/about_5095610_radioactive-isotopes.html