72Hf178.49
Hafnium
Transition Metal
Solid at STP
Period 6Group 4Block DDiscovered 1923
[Xe]6s2 4f14 5d2
Hafnium is a chemical element with symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, making it the penultimate stable element to be discovered (rhenium was identified two years later).
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Atomic Properties
| Atomic Number | 72 |
| Atomic Mass | 178.49 u |
| Electron Configuration | [Xe]6s2 4f14 5d2 |
| Oxidation States | +4 |
| Electronegativity | 1.3 (Pauling) |
| Atomic Radius | 212 pm |
| Ionization Energy | 6.825 eV |
| Block | D |
Physical Properties
| Appearance | steel gray |
| Standard State | Solid |
| Melting Point | 2506 K (2232.8 °C) |
| Boiling Point | 4876 K (4602.9 °C) |
| Density | 13.3 g/cm³ |
| Molar Heat | 25.73 J/(mol·K) |
| CPK Color | #4DC2FF |
Classification
| Category | Transition Metal |
| Group Block | Transition metal |
| Period | 6 |
| Group | 4 |
| Block | D |
Discovery
| Year Discovered | 1923 |
| Discovered By | Dirk Coster |
| Electron Shells | 2, 8, 18, 32, 10, 2 |