Most of the isotope data on this site has been obtained from the National Nuclear Data Center.
Naturally Occurring Isotopes
Francium has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 199 | 12 milliseconds | Alpha Decay | > 0.00% |
| Electron Capture | No Data Available | ||
| 200 | 49 milliseconds | Alpha Decay | 100.00% |
| 201 | 62 milliseconds | Alpha Decay | 100.00% |
| 201m | 19 milliseconds | Alpha Decay | 100.00% |
| 202 | 0.30 seconds | Alpha Decay | 100.00% |
| 202m | 0.29 seconds | Alpha Decay | 100.00% |
| 203 | 0.55 seconds | Alpha Decay | <= 100.00% |
| 204 | 1.8 seconds | Alpha Decay | 92.00% |
| Electron Capture | 8.00% | ||
| 204m | 1.6 seconds | Alpha Decay | 90.00% |
| Electron Capture | 10.00% | ||
| 204m1 | 0.8 seconds | Alpha Decay | 74.00% |
| Electron Capture | 26.00% | ||
| 205 | 3.97 seconds | Alpha Decay | 98.50% |
| Electron Capture | 1.50% | ||
| 206 | ≈ 16 seconds | Alpha Decay | ~ 84.00% |
| Electron Capture | ~ 16.00% | ||
| Electron Capture | ~ 16.00% | ||
| Alpha Decay | ~ 84.00% | ||
| 206m | 0.7 seconds | Isomeric Transition | 95.00% |
| Alpha Decay | 5.00% | ||
| 207 | 14.8 seconds | Alpha Decay | 95.00% |
| Electron Capture | 5.00% | ||
| 208 | 59.1 seconds | Alpha Decay | 89.00% |
| Electron Capture | 11.00% | ||
| 209 | 50.5 seconds | Alpha Decay | 89.00% |
| Electron Capture | 11.00% | ||
| 210 | 3.18 minutes | Alpha Decay | 71.00% |
| Electron Capture | 29.00% | ||
| 211 | 3.10 minutes | Alpha Decay | 87.00% |
| Electron Capture | 13.00% | ||
| 212 | 20.0 minutes | Electron Capture | 57.00% |
| Alpha Decay | 43.00% | ||
| 213 | 34.82 seconds | Alpha Decay | 99.44% |
| Electron Capture | 0.56% | ||
| 214 | 5.0 milliseconds | Alpha Decay | 100.00% |
| 214m | 3.35 milliseconds | Alpha Decay | 100.00% |
| 215 | 86 nanoseconds | Alpha Decay | 100.00% |
| 216 | 700 nanoseconds | Alpha Decay | 100.00% |
| 217 | 19 microseconds | Alpha Decay | 100.00% |
| 218 | 1.0 milliseconds | Alpha Decay | 100.00% |
| 218m | 22.0 milliseconds | Alpha Decay | <= 100.00% |
| Isomeric Transition | No Data Available | ||
| 219 | 20 milliseconds | Alpha Decay | 100.00% |
| 220 | 27.4 seconds | Alpha Decay | 99.65% |
| Beta-minus Decay | 0.35% | ||
| 221 | 286.1 seconds | Alpha Decay | 100.00% |
| Beta-minus Decay | < 0.10% | ||
| 222 | 14.2 minutes | Beta-minus Decay | 100.00% |
| 223 | 22.00 minutes | Alpha Decay | 6.0×10-3 % |
| Beta-minus Decay | 99.99% | ||
| 224 | 3.33 minutes | Beta-minus Decay | 100.00% |
| 225 | 3.95 minutes | Beta-minus Decay | 100.00% |
| 226 | 49 seconds | Beta-minus Decay | 100.00% |
| 227 | 2.47 minutes | Beta-minus Decay | 100.00% |
| 228 | 38 seconds | Beta-minus Decay | <= 100.00% |
| 229 | 50.2 seconds | Beta-minus Decay | 100.00% |
| 230 | 19.1 seconds | Beta-minus Decay | 100.00% |
| 231 | 17.6 seconds | Beta-minus Decay | 100.00% |
| 232 | 5.5 seconds | Beta-minus Decay | 100.00% |
| 233 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
This page is maintained by Steve Gagnon.