Plutonium
actinide · period 7 · group 3 · f-block
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized.
What the numbers say
At standard temperature and pressure Plutonium is a solid, sitting in period 7, group 3 of the f-block.
Its melting point of 913 K (639 °C) is the 68th highest of the 110 elements with a measured value — mid-range among the elements.
At 19.816 g/cm³ it is the 6th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.28. Paired with oxygen (3.44) that is a difference of 2.16, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a simple monoclinic structure.
It is reported in 6 oxidation states (3, 4, 5, 6, 7, 8), which sets how many distinct compounds and phases it can form.
First identified in 1940.
Crystal structure
Solid Plutonium adopts a Simple Monoclinic arrangement, in the Monoclinic system — axes a ≠ b ≠ c, angles α = γ = 90°, β ≠ 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 Pu — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 32 · O 24 · P 8 · Q 2
Properties
| Atomic number | 94 |
|---|---|
| Atomic mass | 244 u |
| Series | actinide |
| Group | 3 |
| Period | 7 |
| Block | f-block |
| Phase at STP | Solid |
| Density | 19.816 g/cm³ |
| Melting point | 912.5 K (639 °C) |
| Boiling point | 3505 K (3232 °C) |
| Electronegativity (Pauling) | 1.28 |
| Electron configuration | [Rn] 5f⁶ 7s² |
| Crystal structure | Simple Monoclinic |
| Oxidation states | 3,4,5,6,7,8 |
| Discovered | 1940 |
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See Pu in context with all 118 elements.
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