| M Formula: | NpO2 |
| Properties: | |
| Dark-olive, free-flowing powder. | |
| Derivation: | |
| Neptunium oxalate is precipitated from solutions containing nitric acid and neptunium. The neptunium oxalate is calcined at 500–550C, producing neptunium dioxide. | |
| Hazard: | |
| Toxic. A radioactive poison. | |
| Use: | |
| Fabrication by powder metallurgy into target elements to be irradiated to produce Pu-238. | |