Curium
actinide · period 7 · group 3 · f-block
Curium is a transuranic radioactive chemical element with the symbol Cm and atomic number 96. This element of the actinide series was named after Marie and Pierre Curie, both known for their research on radioactivity.
What the numbers say
At standard temperature and pressure Curium is a solid, sitting in period 7, group 3 of the f-block.
Its melting point of 1613 K (1340 °C) is the 37th highest of the 110 elements with a measured value — mid-range among the elements.
At 13.51 g/cm³ it is the 16th 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 hexagonal structure — hexagonal packing offers few easy slip systems, so properties are anisotropic and formability is limited.
It is reported in 2 oxidation states (3, 4), which sets how many distinct compounds and phases it can form.
First identified in 1944.
Crystal structure
Solid Curium adopts a Simple Hexagonal arrangement, in the Hexagonal system — axes a = b ≠ c, angles α = β = 90°, γ = 120°. 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 Cm — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 32 · O 25 · P 9 · Q 2
Properties
| Atomic number | 96 |
|---|---|
| Atomic mass | 247 u |
| Series | actinide |
| Group | 3 |
| Period | 7 |
| Block | f-block |
| Phase at STP | Solid |
| Density | 13.51 g/cm³ |
| Melting point | 1613 K (1340 °C) |
| Boiling point | 3383 K (3110 °C) |
| Electronegativity (Pauling) | 1.28 |
| Electron configuration | [Rn] 5f⁷ 6d¹ 7s² |
| Crystal structure | Simple Hexagonal |
| Oxidation states | 3,4 |
| Discovered | 1944 |
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See Cm in context with all 118 elements.
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