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List of Radioactive Elements

Radioactive Elements and Their Most Stable Isotopes

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This symbol warns of a radiation hazard.

This symbol warns of a radiation hazard.

fStop Images - Jutta Kuss, Getty Images

This is a list or table of elements that are radioactive. All elements have radioactive isotopes. This table contains the elements that have no stable isotopes. Each element is followed by the most stable known isotope and its half-life.

This list is sorted by increasing atomic number.

Reference: International Atomic Energy Agency ENSDF database (Oct 2010)

Radioactive Elements

Element Most Stable Isotope Half-life
of Most Stable Istope
Technetium Tc-91 4.21 x 106 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 104 years
Protactinium Pa-231 3.28 x 104 years
Uranium U-236 2.34 x 107 years
Neptunium Np-237 2.14 x 106 years
Plutonium Pu-244 8.00 x 107 years
Americium Am-243 7370 years
Curium Cm-247 1.56 x 107 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
Lawrencium Lr-262 4 hours
Rutherfordium Rf-265 13 hours
Dubnium Db-268 32 hours
Seaborgium Sg-271 2.4 minutes
Bohrium Bh-267 17 seconds
Hassium Hs-269 9.7 seconds
Meitnerium Mt-276 0.72 seconds
Darmstadtium Ds-281 11.1 seconds
Roentgenium Rg-281 26 seconds
Copernicium Cn-285 29 seconds
Ununtrium Uut-284 0.48 seconds
Flerovium Fl-289 2.65 seconds
Ununpentium Uup-289 87 milliseconds
Livermorium Lv-293; 61 milliseconds
Ununseptium Unknown  
Ununoctium Uuo-294 1.8 milliseconds

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