Most of the isotope data on this site has been obtained from the National Nuclear Data Center.
Naturally Occurring Isotopes
Radium has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 201 | 1.6 milliseconds | Alpha Decay | 100.00% |
| Electron Capture | No Data Available | ||
| 202 | 16 milliseconds | Alpha Decay | 100.00% |
| 203 | 31 milliseconds | Alpha Decay | 100.00% |
| 203m | 24 milliseconds | Alpha Decay | 100.00% |
| 204 | 57 milliseconds | Alpha Decay | 100.00% |
| 205 | 210 milliseconds | Alpha Decay | <= 100.00% |
| Electron Capture | No Data Available | ||
| 205m | 170 milliseconds | Alpha Decay | <= 100.00% |
| Electron Capture | No Data Available | ||
| 206 | 0.24 seconds | Alpha Decay | 100.00% |
| 207 | 1.35 seconds | Alpha Decay | ~ 86.00% |
| Electron Capture | ~ 14.00% | ||
| 207m | 59 milliseconds | Isomeric Transition | >= 85.00% |
| Alpha Decay | <= 15.00% | ||
| 208 | 1.3 seconds | Alpha Decay | 95.00% |
| Electron Capture | 5.00% | ||
| 209 | 4.6 seconds | Alpha Decay | ~ 90.00% |
| Electron Capture | ~ 10.00% | ||
| 210 | 3.7 seconds | Alpha Decay | ~ 96.00% |
| Electron Capture | ~ 4.00% | ||
| 211 | 13 seconds | Alpha Decay | > 93.00% |
| Electron Capture | < 7.00% | ||
| 212 | 13.0 seconds | Alpha Decay | ~ 85.00% |
| Electron Capture | ~ 15.00% | ||
| 213 | 2.73 minutes | Alpha Decay | 80.00% |
| Electron Capture | 20.00% | ||
| 213m | 2.20 milliseconds | Isomeric Transition | ~ 99.40% |
| Alpha Decay | ~ 0.60% | ||
| 214 | 2.46 seconds | Alpha Decay | 99.94% |
| Electron Capture | 0.06% | ||
| 215 | 1.55 milliseconds | Alpha Decay | 100.00% |
| 216 | 182 nanoseconds | Alpha Decay | 100.00% |
| Electron Capture | < 1.0×10-8 % | ||
| 217 | 1.6 microseconds | Alpha Decay | 100.00% |
| 218 | 25.2 microseconds | Alpha Decay | 100.00% |
| 219 | 10 milliseconds | Alpha Decay | 100.00% |
| 220 | 18 milliseconds | Alpha Decay | 100.00% |
| 221 | 28 seconds | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 1×10-12 % | ||
| 222 | 38.0 seconds | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 3.0×10-8 % | ||
| 223 | 11.43 days | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 8.9×10-8 % | ||
| 224 | 3.6319 days | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 4.0×10-9 % | ||
| 225 | 14.9 days | Beta-minus Decay | 100.00% |
| 226 | 1600 years | Alpha Decay | 100.00% |
| Emission of a carbon-14 nucleus | 3.2×10-9 % | ||
| 227 | 42.2 minutes | Beta-minus Decay | 100.00% |
| 228 | 5.75 years | Beta-minus Decay | 100.00% |
| 229 | 4.0 minutes | Beta-minus Decay | No Data Available |
| 230 | 93 minutes | Beta-minus Decay | 100.00% |
| 231 | 104.1 seconds | Beta-minus Decay | 100.00% |
| 232 | 4.2 minutes | Beta-minus Decay | 100.00% |
| 233 | 30 seconds | Beta-minus Decay | 100.00% |
| 234 | 30 seconds | Beta-minus Decay | 100.00% |
| 235 | No Data Available | No Data Available | No Data Available |
This page is maintained by Steve Gagnon.