Hafnium
Element 72 · Transition Metal
Hafnium is a lustrous, corrosion-resistant metal that looks and behaves much like its lighter twin, zirconium — the two are so alike that separating them delayed hafnium's discovery until 1923. It melts high, resists acids, and almost always takes the +4 state.
Its neutron appetite makes hafnium ideal for reactor control rods, while hafnium dioxide's insulating power shrank transistors when chipmakers adopted it as a gate dielectric. It also tips plasma cutters and strengthens superalloys.
Key facts
| Atomic number | 72 |
|---|---|
| Atomic weight | 178.49 |
| Category | Transition Metal |
| Group / Period | 4 / 6 |
| Block | d |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d2 |
| Common oxidation states | +4 |
| State at STP | Solid |
| Electronegativity | 1.30 |
| Density | 13.31 g/cm³ |
| Melting point | 2233 °C |
| Boiling point | 4603 °C |
Occurrence
Hafnium is always found with zirconium in the mineral zircon (zirconium silicate), typically at about one part hafnium to fifty parts zirconium.
Applications
Nuclear reactor control rods
HfO2 gate insulators in computer chips
Plasma cutting electrodes
High-temperature superalloys
Common compounds
- hafnium dioxide
- hafnium tetrachloride
Hafnium hides inside zirconium ore and the two are nearly identical twins — separating them was so hard it delayed hafnium's discovery until 1923.
Data source: IUPAC standard atomic weights 2021