A radioactive element does not have any stable isotopes, which means it may spontaneously degenerate. Radioactive elements include uranium, curium and thorium.All elements that have an atomic number higher than 83 are considered radioactive. These elements do not have stable isotopes, which is the primary thing that defines them as radioactive elements.
Some radioactive elements are
Element | Most Stable Isotope | Half-life of Most Stable Istope |
Technetium | Tc-91 | 4.21 x 10^{6} years |
Promethium | Pm-145 | 17.4 years |
Polonium | Po-209 | 102 years |
Astatine | At-210 | 8.1 hours |
Radon | Rn-222 | 3.82 days |
Francium | Fr-223 | 22 minutes |
Radium | Ra-226 | 1600 years |
Actinium | Ac-227 | 21.77 years |
Thorium | Th-229 | 7.54 x 10^{4} years |
Protactinium | Pa-231 | 3.28 x 10^{4} years |
Uranium | U-236 | 2.34 x 10^{7} years |
Neptunium | Np-237 | 2.14 x 10^{6} years |
Plutonium | Pu-244 | 8.00 x 10^{7} years |
Americium | Am-243 | 7370 years |
Curium | Cm-247 | 1.56 x 10^{7} years |
Berkelium | Bk-247 | 1380 years |
Californium | Cf-251 | 898 years |
Einsteinium | Es-252 | 471.7 days |
Fermium | Fm-257 | 100.5 days |
Mendelevium | Md-258 | 51.5 days |
Nobelium | No-259 | 58 minutes |