List of Radioactive Elements

Radioactive Elements and Their Most Stable Isotopes

uranium periodic table
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This is a list or table of elements that are radioactive. Keep in mind, all elements can have radioactive isotopes. If enough neutrons are added to an atom, it becomes unstable and decays. A good example of this is tritium, a radioactive isotope of hydrogen naturally present at extremely low levels. This table contains the elements that have no stable isotopes. Each element is followed by the most stable known isotope and its half-life.

Note increasing atomic number doesn't necessarily make an atom more unstable. Scientists predict there may be islands of stability in the periodic table, where superheavy transuranium elements may be more stable (although still radioactive) than some lighter elements.

This list is sorted by increasing atomic number.

Radioactive Elements

ElementMost Stable IsotopeHalf-life
of Most Stable Istope
TechnetiumTc-914.21 x 106 years
PromethiumPm-14517.4 years
PoloniumPo-209102 years
AstatineAt-2108.1 hours
RadonRn-2223.82 days
FranciumFr-22322 minutes
RadiumRa-2261600 years
ActiniumAc-22721.77 years
ThoriumTh-2297.54 x 104 years
ProtactiniumPa-2313.28 x 104 years
UraniumU-2362.34 x 107 years
NeptuniumNp-2372.14 x 106 years
PlutoniumPu-2448.00 x 107 years
AmericiumAm-2437370 years
CuriumCm-2471.56 x 107 years
BerkeliumBk-2471380 years
CaliforniumCf-251898 years
EinsteiniumEs-252471.7 days
FermiumFm-257100.5 days
MendeleviumMd-25851.5 days
NobeliumNo-25958 minutes
LawrenciumLr-2624 hours
RutherfordiumRf-26513 hours
DubniumDb-26832 hours
SeaborgiumSg-2712.4 minutes
BohriumBh-26717 seconds
HassiumHs-2699.7 seconds
MeitneriumMt-2760.72 seconds
DarmstadtiumDs-28111.1 seconds
RoentgeniumRg-28126 seconds
CoperniciumCn-28529 seconds
NihoniumNh-2840.48 seconds
FleroviumFl-2892.65 seconds
MoscoviumMc-28987 milliseconds
LivermoriumLv-29361 milliseconds
TennessineUnknown 
OganessonOg-2941.8 milliseconds

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