[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
Neptunium has no naturally occurring isotopes.
Known Isotopes
| Mass Number | Half-life | Decay Mode | Branching Percentage |
| 225 | No Data Available | Alpha Decay | 100.00% |
| 226 | 35 milliseconds | Alpha Decay | 100.00% |
| 227 | 0.51 seconds | Alpha Decay | 100.00% |
| 228 | 61.4 seconds | Electron Capture | 60.00% |
| Alpha Decay | 40.00% | ||
| 229 | 4.0 minutes | Alpha Decay | 68.00% |
| Electron Capture | 32.00% | ||
| 230 | 4.6 minutes | Electron Capture | <= 97.00% |
| Alpha Decay | >= 3.00% | ||
| 231 | 48.8 minutes | Electron Capture | 98.00% |
| Alpha Decay | 2.00% | ||
| 232 | 14.7 minutes | Electron Capture | 100.00% |
| Alpha Decay | 2.0×10-4 % | ||
| 233 | 36.2 minutes | Electron Capture | 100.00% |
| Alpha Decay | <= 1.0×10-3 % | ||
| 234 | 4.4 days | Electron Capture | 100.00% |
| 235 | 396.1 days | Electron Capture | 100.00% |
| Alpha Decay | 2.6×10-3 % | ||
| 236 | 153×10+3 years | Electron Capture | 86.30% |
| Beta-minus Decay | 13.50% | ||
| Alpha Decay | 0.16% | ||
| 236m | 22.5 hours | Beta-minus Decay | 50.00% |
| Electron Capture | 50.00% | ||
| 237 | 2.144×10+6 years | Alpha Decay | 100.00% |
| Spontaneous Fission | <= 2×10-10 % | ||
| 238 | 2.117 days | Beta-minus Decay | 100.00% |
| 239 | 2.356 days | Beta-minus Decay | 100.00% |
| 240 | 61.9 minutes | Beta-minus Decay | 100.00% |
| 240m | 7.22 minutes | Beta-minus Decay | 99.88% |
| Isomeric Transition | 0.12% | ||
| 241 | 13.9 minutes | Beta-minus Decay | 100.00% |
| 242 | 2.2 minutes | Beta-minus Decay | 100.00% |
| 242m | 5.5 minutes | Beta-minus Decay | 100.00% |
| 243 | 1.85 minutes | Beta-minus Decay | 100.00% |
| 244 | 2.29 minutes | Beta-minus Decay | 100.00% |
| 245 | No Data Available | No Data Available | No Data Available |
This page is maintained by Steve Gagnon.