93Solid
Np 237 Atomic mass · uActinides
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.
Discovery 1940 (Edwin McMillan)
K2L8M18N32O22P9Q2
Physical properties
Values for the element in its standard state.
- Density
- 20.45g/cm³
- Melting point
- 917K
- Boiling point
- 4,273K
- Atomic radius
- Not available
- Bonding type
- Metallic
- Molar heat
- 29.46J/(mol·K)
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 4f, 14 electrons; 5d, 10 electrons; 6s, 2 electrons; 6p, 6 electrons; 5f, 4 electrons; 6d, 1 electrons; 7s, 2 electrons;
[Rn] represents 86 core electrons. The full view shows them explicitly.
93 electrons Orbital order preserved from source
- Electronegativity
- 1.36Pauling scale
- First ionization energy
- 605kJ/mol
- Electron affinity
- Not available
- Van der Waals radius
- Not available
Np NeptuniumAtomic number 93
605kJ/mol
Atomic numberGaps indicate unavailable data
About neptunium
- Appearance
- Silvery metallic
- Discovery
- 1940 (Edwin McMillan)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.