Np
Neptunium
Element 93 · 237.04817 u
Neptunium was the first transuranium element discovered.
Physical Properties
| Atomic Mass | 237.04817 u |
| Density | 20.45 g/cm³ |
| Melting Point | 917.0 K |
| Boiling Point | 4273.0 K |
| Appearance | Silvery metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 1.36 (Pauling) |
| 1st Ionization Energy | 604.5 kJ/mol |
| Electron Affinity | 45.85 kJ/mol |
| Oxidation States | +3, +4, +5, +6, +7 |
Atomic Properties
| Electron Configuration | [Rn] 5f4 6d1 7s2 |
| Atomic Radius | 155.0 pm |
| Van der Waals Radius | 221.0 pm |
Discovery
| Discovered By | Edwin McMillan, Philip Abelson |
| Discovery Year | 1940 |
| Location | Berkeley, California, USA |
| Named After | Named after the planet Neptune, following uranium (Uranus) |
About Neptunium
Neptunium is a silvery radioactive actinide and the first transuranium element discovered. It is produced as a byproduct in nuclear reactors.
Uses & Applications
Neutron detection, precursor for plutonium-238 (space probes), and nuclear research.
Fun Fact
Neptunium was the first synthetic transuranium element, opening the door to all heavier elements.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 236 | - | 154,000 years | No |
| 237 | - | 2.144 million years | No |
Electron Configuration
[Rn] 5f4 6d1 7s2