Neptunium
actinide · period 7 · group 3 · f-block
Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element.
What the numbers say
At standard temperature and pressure Neptunium is a solid, sitting in period 7, group 3 of the f-block.
Its melting point of 912 K (639 °C) is the 69th highest of the 110 elements with a measured value — mid-range among the elements.
At 20.45 g/cm³ it is the 5th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.36. Paired with oxygen (3.44) that is a difference of 2.08, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a simple orthorhombic structure.
It is reported in 5 oxidation states (3, 4, 5, 6, 7), which sets how many distinct compounds and phases it can form.
First identified in 1940.
Crystal structure
Solid Neptunium adopts a Simple Orthorhombic arrangement, in the Orthorhombic system — axes a ≠ b ≠ c, angles α = β = γ = 90°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Np — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 32 · O 22 · P 9 · Q 2
Properties
| Atomic number | 93 |
|---|---|
| Atomic mass | 237 u |
| Series | actinide |
| Group | 3 |
| Period | 7 |
| Block | f-block |
| Phase at STP | Solid |
| Density | 20.45 g/cm³ |
| Melting point | 912 K (639 °C) |
| Boiling point | 4447 K (4174 °C) |
| Electronegativity (Pauling) | 1.36 |
| Electron configuration | [Rn] 5f⁴ 6d¹ 7s² |
| Crystal structure | Simple Orthorhombic |
| Oxidation states | 3,4,5,6,7 |
| Discovered | 1940 |
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See Np in context with all 118 elements.
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