72HfHafnium178.486 u
Hafnium (Hf)
Hafnium is a transition metal with atomic number 72, in period 6 and group 4 of the periodic table. Its atomic mass is 178.486 u and its electron configuration is [Xe] 4f¹⁴ 5d² 6s². Solid at 25 °C.
Key facts
| Atomic number | 72 |
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| Atomic mass | 178.486 u |
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| Category | Transition Metal |
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| Period | 6 |
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| Group | 4 |
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| Block | d |
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| Electron configuration | [Xe] 4f¹⁴ 5d² 6s² |
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| Electrons per shell | 2, 8, 18, 32, 10, 2 |
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| Electronegativity (Pauling) | 1.3 |
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| Oxidation states | −2, +1, +2, +3, +4common in bold |
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| State at 25 °C | Solid |
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| Melting point | 2506 K2232.85 °C |
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| Boiling point | 4876 K4602.85 °C |
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| Density | 13.31 g/cm³ |
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Atomic properties
| First ionization energy | 6.825 eV |
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| Electron affinity | 0 kJ/mol |
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| Atomic radius | 167 pm |
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| Covalent radius | 175 pm |
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| Van der Waals radius | 212 pm |
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| Common ions | Hf⁴⁺ |
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| Protons, neutrons, electrons | 72, 106, 72 |
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Physical and thermal properties
| Molar volume | 13.44 cm³/mol |
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| Heat of fusion | 25.5 kJ/mol |
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| Heat of vaporization | 630 kJ/mol |
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| Specific heat | 144 J/(kg·K) |
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| Thermal conductivity | 23 W/(m·K) |
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| Thermal expansion | 5.9 × 10⁻⁶ K⁻¹ |
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| Mohs hardness | 5.5 |
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| Young’s modulus | 78 GPa |
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| Crystal structure | Simple hexagonal |
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| Magnetic type | Paramagnetic |
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Identification and history
| CAS number | 7440-58-6 |
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| Latin name | Hafnium |
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| Discovered by | D. Coster, G. de Hevesy · 1923 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 174Hf | 173.940048 | 0.16 % |
| 176Hf | 175.94141 | 5.26 % |
| 177Hf | 176.94323 | 18.6 % |
| 178Hf | 177.943708 | 27.28 % |
| 179Hf | 178.945826 | 13.62 % |
| 180Hf | 179.94656 | 35.08 % |
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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Periodic Table