Hf
Hafnium
HAFNIUM
TRANSITION ELEMENT: TITANIUM GROUP
| Atomic number: | 72 |
| Group numbers: | 4 |
| Period: | 6 |
| Electronic configuration: | [Xe] 4f14 5d2 6s2 |
| Formal oxidation number: | +4 |
| Electronegativities: | 1.3 |
| Atomic radius / pm: | 156.4 |
| Relative atomic mass: | 178.49(2) |
Hafnium was discovered by Dirk Coster (NL) and George Charles von Hevesy (HU) in 1923. The origin of the name comes from the Latin name Hafnia meaning Copenhagen. It is a silvery, ductile, toxic metal that resists alkalis and acids (except HF). Metal ignites and burns readily and the exposed surfaces form oxide film. Hafnium is obtained from mineral zircon or baddeleyite. It is used in reactor control rods because of its ability to absorb neutrons. The price of 99.9 % pure hafnium pieces is 260.60 € for 50 g.
| Density / g dm-3: | 13310 | (293 K) |
| 12000 | (m.p.) | |
| Molar volume / cm3mol-1: | 13.41 | (293 K) |
| 14.87 | (m.p.) | |
| Electrical resistivity / µΩcm: | 33.08 | (20 °C) |
| Thermal conductivity / W m-1K-1: | 23 |
| Melting point / °C: | 2233 |
| Boiling point / °C: | 4603 |
| Heat of fusion / kJ mol-1: | 25.5 |
| Heat of vaporization / kJ mol-1: | 570.7 |
| Heat of atomization / kJ mol-1: | 618.9 |
| First ionization energy / kJ mol-1: | 658.52 |
| Second ionization energy / kJ mol-1: | 1437.64 |
| Third ionization energy / kJ mol-1: | 2248.12 |
| in the atmosphere / ppm: | - |
| in the Earth's crust / ppm: | 3 |
| in the oceans / ppm: | 0.008 |
| Crystal structure: | hexagonal |
| Unit-cell dimensions / pm: | a=319.46, c=505.10 |
| Space group: | P63/mmc |
| Isotope | Relative atomic mass | Mass percent (%) |
|---|---|---|
| 174Hf | 173.940040(3) | 0.162(3) |
| 176Hf | 175.941402(3) | 5.206(5) |
| 177Hf | 176.943220(3) | 18.606(4) |
| 178Hf | 177.943698(3) | 27.297(4) |
| 179Hf | 178.945815(3) | 13.629(6) |
| 180Hf | 179.946549(3) | 35.100(7) |
| Balanced half-reaction | Eo / V | |
|---|---|---|
| Hf4+ + 4e- → Hf(s) | - 1.70 | |
| HfO2(s) + 4H+ + 4e- → Hf(s) + 2H2O | - 1.57 | |
| HfO2+ + 2H+ + 4e- → Hf(s) + H2O | - 1.70 | |
| HfO(OH)2(s) + H2O + 4e- → Hf(s) + 4OH- | - 2.50 |
| 71 Lutetium | ← | 72 Hafnium | → | 73 Tantalum |
Citing this page:
Generalic, Eni. "Hafnium." EniG. Periodic Table of the Elements. KTF-Split, 18 Jan. 2024. Web. {Date of access}. <https://www.periodni.com/hf.html>.
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