Hafnium
transition metal · period 6 · group 4 · d-block
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals.
What the numbers say
At standard temperature and pressure Hafnium is a solid, sitting in period 6, group 4 of the d-block.
Its melting point of 2506 K (2233 °C) is the 10th highest of the 110 elements with a measured value — one of the most refractory elements there is.
At 13.31 g/cm³ it is the 17th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.3. Paired with oxygen (3.44) that is a difference of 2.14, 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 3 oxidation states (2, 3, 4), which sets how many distinct compounds and phases it can form.
First identified in 1923.
Crystal structure
Solid Hafnium 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 Hf — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 32 · O 10 · P 2
Properties
| Atomic number | 72 |
|---|---|
| Atomic mass | 178.492 u |
| Series | transition metal |
| Group | 4 |
| Period | 6 |
| Block | d-block |
| Phase at STP | Solid |
| Density | 13.31 g/cm³ |
| Melting point | 2506 K (2233 °C) |
| Boiling point | 4876 K (4603 °C) |
| Electronegativity (Pauling) | 1.3 |
| Electron configuration | [Xe] 4f¹⁴ 5d² 6s² |
| Crystal structure | Simple Hexagonal |
| Oxidation states | 2,3,4 |
| Discovered | 1923 |
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See Hf in context with all 118 elements.
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