Most of the isotope data on this site has been obtained from the National Nuclear Data Center.
Naturally Occurring Isotopes
Astatine has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 191 | 1.7 milliseconds | Alpha Decay | 100.00% |
| 191m | 2.1 milliseconds | Alpha Decay | 100.00% |
| 192 | 11.5 milliseconds | Alpha Decay | 100.00% |
| 192m | 88 milliseconds | Alpha Decay | 100.00% |
| 193 | 28 milliseconds | Alpha Decay | 100.00% |
| 193m | 21 milliseconds | Alpha Decay | 100.00% |
| 193m1 | 27 milliseconds | Alpha Decay | 24.00% |
| Isomeric Transition | 76.00% | ||
| 194 | 310 milliseconds | Alpha Decay | No Data Available |
| 194m | 253 milliseconds | Alpha Decay | No Data Available |
| 195 | 328 milliseconds | Alpha Decay | 100.00% |
| 195m | 147 milliseconds | Alpha Decay | 100.00% |
| 196 | 0.388 seconds | Alpha Decay | ~ 95.10% |
| Electron Capture | ~ 4.90% | ||
| 197 | 0.388 seconds | Alpha Decay | 96.10% |
| Electron Capture | 3.90% | ||
| 197m | 2.0 seconds | Electron Capture | No Data Available |
| Isomeric Transition | <= 4.0×10-3 % | ||
| Alpha Decay | <= 100.00% | ||
| 198 | 3.8 seconds | Alpha Decay | 90.00% |
| Electron Capture | 10.00% | ||
| 198m | 1.04 seconds | Alpha Decay | 84.00% |
| Electron Capture | 16.00% | ||
| 199 | 7.03 seconds | Alpha Decay | 90.00% |
| Electron Capture | 10.00% | ||
| 200 | 43 seconds | Alpha Decay | 52.00% |
| Electron Capture | 48.00% | ||
| 200m | 47 seconds | Alpha Decay | 43.00% |
| Electron Capture | <= 57.00% | ||
| 200m1 | 7.3 seconds | Electron Capture | < 89.50% |
| Isomeric Transition | < 89.50% | ||
| Alpha Decay | ~ 10.50% | ||
| 201 | 85.2 seconds | Alpha Decay | 71.00% |
| Electron Capture | 29.00% | ||
| 202 | 184 seconds | Electron Capture | 63.00% |
| Alpha Decay | 37.00% | ||
| 202m | 182 seconds | Electron Capture | 91.30% |
| Alpha Decay | 8.70% | ||
| 202m1 | 0.46 seconds | Alpha Decay | 0.10% |
| Isomeric Transition | 99.90% | ||
| 203 | 7.4 minutes | Electron Capture | 69.00% |
| Alpha Decay | 31.00% | ||
| 204 | 9.12 minutes | Electron Capture | 96.09% |
| Alpha Decay | 3.91% | ||
| 204m | 108 milliseconds | Isomeric Transition | 100.00% |
| 205 | 26.9 minutes | Electron Capture | 90.00% |
| Alpha Decay | 10.00% | ||
| 206 | 30.6 minutes | Electron Capture | 99.10% |
| Alpha Decay | 0.90% | ||
| 207 | 1.81 hours | Electron Capture | 91.40% |
| Alpha Decay | 8.60% | ||
| 208 | 1.63 hours | Electron Capture | 99.45% |
| Alpha Decay | 0.55% | ||
| 209 | 5.41 hours | Electron Capture | 95.90% |
| Alpha Decay | 4.10% | ||
| 210 | 8.1 hours | Electron Capture | 99.82% |
| Alpha Decay | 0.18% | ||
| 211 | 7.214 hours | Electron Capture | 58.20% |
| Alpha Decay | 41.80% | ||
| 212 | 0.314 seconds | Electron Capture | < 0.03% |
| Beta-minus Decay | < 2.0×10-6 % | ||
| Alpha Decay | 100.00% | ||
| 212m | 0.119 seconds | Alpha Decay | > 99.00% |
| Isomeric Transition | < 1.00% | ||
| 213 | 125 nanoseconds | Alpha Decay | 100.00% |
| 214 | 558 nanoseconds | Alpha Decay | 100.00% |
| 215 | 0.10 milliseconds | Alpha Decay | 100.00% |
| 216 | 0.30 milliseconds | Alpha Decay | 100.00% |
| Beta-minus Decay | < 6.0×10-3 % | ||
| Electron Capture | < 3.0×10-7 % | ||
| 217 | 32.3 milliseconds | Beta-minus Decay | 7.0×10-3 % |
| Alpha Decay | 99.99% | ||
| 218 | 1.5 seconds | Alpha Decay | 99.90% |
| Beta-minus Decay | 0.10% | ||
| 219 | 56 seconds | Alpha Decay | ~ 97.00% |
| Beta-minus Decay | ~ 3.00% | ||
| 220 | 3.71 minutes | Alpha Decay | 8.00% |
| Beta-minus Decay | 92.00% | ||
| 221 | 2.3 minutes | Beta-minus Decay | 100.00% |
| 222 | 54 seconds | Beta-minus Decay | 100.00% |
| 223 | 50 seconds | Beta-minus Decay | 100.00% |
| 224 | 76 seconds | Beta-minus Decay (suspected) | No Data Available |
| 225 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
| 226 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
| 227 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
| 228 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
| 229 | > 300 nanoseconds | Beta-minus Decay | No Data Available |
| Beta-minus Decay with delayed Neutron Emission | No Data Available |
This page is maintained by Steve Gagnon.