Neptunium
Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
86 is the [Rn] core total across six shells.
At a glance
- Atomic number
- 93
- Atomic mass
- 237 u
- Phase
- Solid
- Density
- 20.45 g/cm³
- Melting point
- 912 K
- Boiling point
- 4,447 K
- First ionization energy
- 604.5 kJ/mol
- Electronegativity
- 1.36
- Electron affinity
- 45.85 kJ/mol
- Molar heat capacity
- 29.46 J/(mol·K)
- Period
- 7
- Appearance
- silvery metallic
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.