[Click for Main Data] Proton Emission Neutron Emission Electron Emission Positron Emission
Most of the isotope data on this site has been obtained from the National Nuclear Data Center.
Naturally Occurring Isotopes
Actinium has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 206 | 22 milliseconds | Alpha Decay | 100.00% |
| 206m | 33 milliseconds | Alpha Decay | 100.00% |
| 207 | 27 milliseconds | Alpha Decay | 100.00% |
| 208 | 95 milliseconds | Alpha Decay | ~ 99.00% |
| Electron Capture | ~ 1.00% | ||
| 208m | 25 milliseconds | Electron Capture | ~ 10.00% |
| Alpha Decay | ~ 90.00% | ||
| 209 | 0.10 seconds | Alpha Decay | ~ 99.00% |
| Electron Capture | ~ 1.00% | ||
| 210 | 0.35 seconds | Alpha Decay | 91.00% |
| Electron Capture | ~ 9.00% | ||
| 211 | 0.21 seconds | Alpha Decay | 100.00% |
| 212 | 0.93 seconds | Alpha Decay | ~ 57.00% |
| Electron Capture | ~ 43.00% | ||
| 213 | 738 milliseconds | Alpha Decay | <= 100.00% |
| 214 | 8.2 seconds | Electron Capture | <= 11.00% |
| Alpha Decay | >= 89.00% | ||
| 215 | 0.17 seconds | Alpha Decay | 99.91% |
| Electron Capture | 0.09% | ||
| 216 | 440 microseconds | Alpha Decay | 100.00% |
| 216m | 441 microseconds | Alpha Decay | 100.00% |
| 217 | 69 nanoseconds | Alpha Decay | 100.00% |
| Electron Capture | <= 2.00% | ||
| 218 | 1.08 microseconds | Alpha Decay | 100.00% |
| 219 | 11.8 microseconds | Alpha Decay | 100.00% |
| 220 | 26.4 milliseconds | Alpha Decay | 100.00% |
| Electron Capture | 5.0×10-4 % | ||
| 221 | 52 milliseconds | Alpha Decay | 100.00% |
| 222 | 5.0 seconds | Alpha Decay | 99.00% |
| Electron Capture | 1.00% | ||
| 222m | 63 seconds | Alpha Decay | >= 88.00% |
| Isomeric Transition | <= 10.00% | ||
| Electron Capture | >= 0.70% | ||
| 223 | 2.10 minutes | Alpha Decay | 99.00% |
| Electron Capture | 1.00% | ||
| 224 | 2.78 hours | Electron Capture | 90.90% |
| Alpha Decay | 9.10% | ||
| Beta-minus Decay | < 1.60% | ||
| 225 | 10.0 days | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 4×10-12 % | ||
| 226 | 29.37 hours | Beta-minus Decay | 83.00% |
| Electron Capture | 17.00% | ||
| Alpha Decay | 6.0×10-3 % | ||
| 227 | 21.772 years | Beta-minus Decay | 98.62% |
| Alpha Decay | 1.38% | ||
| 228 | 6.15 hours | Beta-minus Decay | 100.00% |
| 229 | 62.7 minutes | Beta-minus Decay | 100.00% |
| 230 | 122 seconds | Spontaneous Fission | 1.2×10-6 % |
| Beta-minus Decay | 100.00% | ||
| 231 | 7.5 minutes | Beta-minus Decay | 100.00% |
| 232 | 119 seconds | Beta-minus Decay | 100.00% |
| 233 | 145 seconds | Beta-minus Decay | 100.00% |
| 234 | 44 seconds | Beta-minus Decay | 100.00% |
| 235 | 60 seconds | Beta-minus Decay | 100.00% |
| 236 | No Data Available | Beta-minus Decay (suspected) | No Data Available |
| 237 | No Data Available | No Data Available | No Data Available |
This page is maintained by Steve Gagnon.