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Isotopes of the Element Actinium

[Click for Main Data]

Most of the isotope data on this site has been obtained from the National Nuclear Data Center. Please visit their site for more information.

Naturally Occurring Isotopes

Actinium has no naturally occurring isotopes.

Known Isotopes

Mass NumberHalf-lifeDecay ModeBranching Percentage
20622 millisecondsAlpha Decay100.00%
206m33 millisecondsAlpha Decay100.00%
20727 millisecondsAlpha Decay100.00%
20895 millisecondsAlpha Decay~ 99.00%
Electron Capture~ 1.00%
208m25 millisecondsElectron Capture~ 10.00%
Alpha Decay~ 90.00%
2090.10 secondsAlpha Decay~ 99.00%
Electron Capture~ 1.00%
2100.35 secondsAlpha Decay91.00%
Electron Capture~ 9.00%
2110.21 secondsAlpha Decay100.00%
2120.93 secondsAlpha Decay~ 57.00%
Electron Capture~ 43.00%
213738 millisecondsAlpha Decay<= 100.00%
2148.2 secondsElectron Capture<= 11.00%
Alpha Decay>= 89.00%
2150.17 secondsAlpha Decay99.91%
Electron Capture0.09%
216440 microsecondsAlpha Decay100.00%
216m441 microsecondsAlpha Decay100.00%
21769 nanosecondsAlpha Decay100.00%
Electron Capture<= 2.00%
2181.08 microsecondsAlpha Decay100.00%
21911.8 microsecondsAlpha Decay100.00%
22026.4 millisecondsAlpha Decay100.00%
Electron Capture5.0×10-4 %
22152 millisecondsAlpha Decay100.00%
2225.0 secondsAlpha Decay99.00%
Electron Capture1.00%
222m63 secondsAlpha Decay>= 88.00%
Isomeric Transition<= 10.00%
Electron Capture>= 0.70%
2232.10 minutesAlpha Decay99.00%
Electron Capture1.00%
2242.78 hoursElectron Capture90.90%
Alpha Decay9.10%
Beta-minus Decay< 1.60%
22510.0 daysAlpha Decay100.00%
Emission of a carbon-14 nucleus4×10-12 %
22629.37 hoursBeta-minus Decay83.00%
Electron Capture17.00%
Alpha Decay6.0×10-3 %
22721.772 yearsBeta-minus Decay98.62%
Alpha Decay1.38%
2286.15 hoursBeta-minus Decay100.00%
22962.7 minutesBeta-minus Decay100.00%
230122 secondsSpontaneous Fission1.2×10-6 %
Beta-minus Decay100.00%
2317.5 minutesBeta-minus Decay100.00%
232119 secondsBeta-minus Decay100.00%
233145 secondsBeta-minus Decay100.00%
23444 secondsBeta-minus Decay100.00%
23560 secondsBeta-minus Decay100.00%
236No Data AvailableBeta-minus Decay (suspected)No Data Available
237No Data AvailableNo Data AvailableNo Data Available