[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
Mendelevium has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 245 | 0.90 milliseconds | Alpha Decay | No Data Available |
| Spontaneous Fission | No Data Available | ||
| 245m | 0.35 seconds | Electron Capture | No Data Available |
| Alpha Decay | No Data Available | ||
| 246 | 0.9 seconds | Alpha Decay | 100.00% |
| Electron Capture | > 77.00% | ||
| Alpha Decay | < 23.00% | ||
| Spontaneous Fission (suspected) | No Data Available | ||
| Electron Capture (suspected) | No Data Available | ||
| 247 | 1.2 seconds | Alpha Decay | 99.90% |
| Spontaneous Fission | < 0.10% | ||
| 247m | 0.25 seconds | Alpha Decay | 79.00% |
| Spontaneous Fission | 21.00% | ||
| 248 | 13 seconds | Alpha Decay | 58.00% |
| Electron Capture | 42.00% | ||
| 249 | 21.7 seconds | Alpha Decay | > 60.00% |
| Electron Capture | <= 40.00% | ||
| 249m | 1.9 seconds | Alpha Decay (suspected) | No Data Available |
| 250 | 25 seconds | Alpha Decay | 7.00% |
| Electron Capture | 93.00% | ||
| 251 | 4.3 minutes | Electron Capture | 90.00% |
| Alpha Decay | 10.00% | ||
| 252 | 2.3 minutes | Electron Capture | <= 100.00% |
| 253 | 6 minutes | Electron Capture | <= 100.00% |
| Alpha Decay | No Data Available | ||
| 254 | 28 minutes | Electron Capture | <= 100.00% |
| Electron Capture | <= 100.00% | ||
| 255 | 27 minutes | Electron Capture | 92.00% |
| Alpha Decay | 8.00% | ||
| Spontaneous Fission | < 0.15% | ||
| 256 | 77 minutes | Electron Capture | 90.80% |
| Alpha Decay | 9.20% | ||
| Spontaneous Fission | < 3.00% | ||
| 257 | 5.52 hours | Electron Capture | 85.00% |
| Alpha Decay | 15.00% | ||
| Spontaneous Fission | < 1.00% | ||
| 258 | 51.5 days | Alpha Decay | 100.00% |
| Spontaneous Fission | No Data Available | ||
| 258m | 57.0 minutes | Electron Capture | >= 70.00% |
| Spontaneous Fission | No Data Available | ||
| 259 | 96 minutes | Alpha Decay | < 1.30% |
| Spontaneous Fission | 100.00% | ||
| 260 | 31.8 days | Spontaneous Fission | >= 42.00% |
| Alpha Decay | <= 25.00% | ||
| Electron Capture | <= 23.00% | ||
| Beta-minus Decay | <= 10.00% | ||
| 261 | No Data Available | Alpha Decay (suspected) | No Data Available |
| 262 | No Data Available | Spontaneous Fission (suspected) | No Data Available |
| Alpha Decay (suspected) | No Data Available |
This page is maintained by Steve Gagnon.