Most of the isotope data on this site has been obtained from the National Nuclear Data Center.
Naturally Occurring Isotopes
| Mass Number | Natural Abundance | Half-life |
| 234 | 0.0054% | 2.455×10+5 years |
| 235 | 0.7204% | 7.04×10+8 years |
| 238 | 99.2742% | 4.468×109 years |
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 217 | 16 milliseconds | Alpha Decay | <= 100.00% |
| 218 | 0.51 milliseconds | Alpha Decay | 100.00% |
| 218m | 0.56 milliseconds | Alpha Decay | 100.00% |
| 219 | 42 microseconds | Alpha Decay | 100.00% |
| 220 | No Data Available | Alpha Decay (suspected) | No Data Available |
| Electron Capture (suspected) | No Data Available | ||
| 221 | 700 nanoseconds | No Data Available | No Data Available |
| 222 | 1.0 microseconds | Alpha Decay | 100.00% |
| 223 | 18 microseconds | Alpha Decay | 100.00% |
| Electron Capture | 0.20% | ||
| 224 | 0.9 milliseconds | Alpha Decay | 100.00% |
| 225 | 95 milliseconds | Alpha Decay | 100.00% |
| 226 | 0.35 seconds | Alpha Decay | 100.00% |
| 227 | 1.1 minutes | Alpha Decay | 100.00% |
| 228 | 9.1 minutes | Alpha Decay | > 95.00% |
| Electron Capture | < 5.00% | ||
| 229 | 58 minutes | Electron Capture | ~ 80.00% |
| Alpha Decay | ~ 20.00% | ||
| 230 | 20.8 days | Alpha Decay | 100.00% |
| Spontaneous Fission | < 1×10-10 % | ||
| Emission of a neon-22 nucleus | 5×10-12 % | ||
| 231 | 4.2 days | Electron Capture | 100.00% |
| Alpha Decay | ~ 4.0×10-3 % | ||
| 232 | 68.9 years | Alpha Decay | 100.00% |
| Spontaneous Fission | 3×10-12 % | ||
| 233 | 1.592×10+5 years | Alpha Decay | 100.00% |
| Emission of a neon-24 nucleus | 9×10-10 % | ||
| Spontaneous Fission | < 6×10-11 % | ||
| Emission of a magnesium-28 nucleus | < 1×10-13 % | ||
| 234 | 2.455×10+5 years | Emission of a magnesium nucleus | 1×10-11 % |
| Emission of a neon nucleus | 9×10-12 % | ||
| Alpha Decay | 100.00% | ||
| Spontaneous Fission | 1.6×10-9 % | ||
| 235 | 7.04×10+8 years | Alpha Decay | 100.00% |
| Spontaneous Fission | 7.0×10-9 % | ||
| Emission of a magnesium-28 nucleus | 8×10-10 % | ||
| Emission of a neon nucleus | ~ 8×10-10 % | ||
| 235m | ≈ 26 minutes | Isomeric Transition | 100.00% |
| 236 | 2.342×107 years | Alpha Decay | 100.00% |
| Spontaneous Fission | 9.4×10-8 % | ||
| 237 | 6.75 days | Beta-minus Decay | 100.00% |
| 238 | 4.468×109 years | Spontaneous Fission | 5.5×10-5 % |
| Alpha Decay | 100.00% | ||
| 239 | 23.45 minutes | Beta-minus Decay | 100.00% |
| 240 | 14.1 hours | Beta-minus Decay | 100.00% |
| 241 | No Data Available | Beta-minus Decay (suspected) | No Data Available |
| 242 | 16.8 minutes | Beta-minus Decay | 100.00% |
| 243 | No Data Available | No Data Available | No Data Available |
This page is maintained by Steve Gagnon.