Hafnium (Hf)

Steel-gray metal

Hafnium absorbs neutrons so effectively it controls the chain reaction in nuclear submarines, and with [Xe] 4f¹⁴ 5d² 6s², hafnium has a thermal neutron absorption cross-section of 115 barns—among the highest of any element. It is also used in high-k dielectric chips where HfO₂ replaces SiO₂ as the gate insulator.

Key metrics

Density13.31g/cm³

Melting point2,506K

Boiling point4,876K

Electronegativity1.3Pauling

Discovery

1923discovered

Discovered by: Dirk Coster
Reactivity profile: Corrosion resistant
Reactivity: Low
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Xe]}\; \textcolor{#a855f7}{4_{f}^{14}}\; \textcolor{#22c55e}{5_{d}^{2}}\; \textcolor{#ef4444}{6_{s}^{2}}

[Xe] 4f14 5d2 6s2

Wave function

\Psi_{\text{Hf}} \approx \frac{1}{\sqrt{72!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{72}(\mathbf{r}_{72}) \right|

Probability density $|\Psi|^2$ across the Hf valence shell.

Crystal structure

Hexagonal Close-Packed

Lattice constantsa 1.00 · b 1.00 · c 1.63

Cell anglesα 90° · β 90° · γ 120°

Coordination number12

Atoms per cell2

Atomic packing factor0.74

Physical properties

Atomic radius: 159 pm
Ionization energy: 659 kJ/mol
Electron affinity: 0 kJ/mol
Crystal structure: Hexagonal close-packed (hcp)

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

2506 K4876 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

453.0nmHf I (blue)Blue100%

468.0nmHf IBlue70%

535.1nmHf I (green)Green40%

Dominant line 453.0 nmRange 453–535 nmTransitions 3