| Neptunium | |
| Elemental State | Np |
| Electron Configuration | 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p67s26d15f4 |
| First Ionization Potential | 6.266 eV |
| Electron Affinity | |
| Z* | |
| Pauling Electronegativity | 1.3 |
| Covalent Radius | |
| Metallic Radius | 1.56 Å |
| Ionic Radius | |
| van der Waal's Radius | |
| Melting Point | 644 oC |
| Boiling Point | 3902 oC |
| Density | 20.25 g/cm3 |
| Other Properties | All isotopes are radioactive
237Np half-life = 2.14×106 years |