Americium
actinide · period 7 · group 3 · f-block
Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was named after the Americas. Americium was first produced in 1944 by the group of Glenn T.
What the numbers say
At standard temperature and pressure Americium is a solid, sitting in period 7, group 3 of the f-block.
Its melting point of 1449 K (1176 °C) is the 42nd highest of the 110 elements with a measured value — mid-range among the elements.
At 13.67 g/cm³ it is the 14th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.13. Paired with oxygen (3.44) that is a difference of 2.31, 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 5 oxidation states (2, 3, 4, 5, 6), which sets how many distinct compounds and phases it can form.
First identified in 1944.
Crystal structure
Solid Americium 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 Am — 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 8 · Q 2
Properties
| Atomic number | 95 |
|---|---|
| Atomic mass | 243 u |
| Series | actinide |
| Group | 3 |
| Period | 7 |
| Block | f-block |
| Phase at STP | Solid |
| Density | 13.67 g/cm³ |
| Melting point | 1449 K (1176 °C) |
| Boiling point | 2880 K (2607 °C) |
| Electronegativity (Pauling) | 1.13 |
| Electron configuration | [Rn] 5f⁷ 7s² |
| Crystal structure | Simple Hexagonal |
| Oxidation states | 2,3,4,5,6 |
| Discovered | 1944 |
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See Am in context with all 118 elements.
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