Hafnium is a chemical element wi the seembol Hf an atomic nummer 72. A lustrous, sillery gray, tetravalent transeetion metal, hafnium chemically resembles zirconium an is foond in zirconium minerals. Its existence wis predictit bi Dmitri Mendeleev in 1869. Hafnium wis the penultimate stable isotope element tae be discovered (rhenium wis identified twa year later). Hafnium is named efter Hafnia, the Latin name for Copenhagen, whaur it wis discovered.
Hafnium, 72Hf |
Hafnium |
---|
Pronunciation | (HAF-nee-əm) |
---|
Appearance | steel gray |
---|
Standard atomic weight Ar, std(Hf) | 7002178490000000000♠178.49(2)[1] |
---|
Hafnium in the periodic cairt |
---|
|
Atomic nummer (Z) | 72 |
---|
Group | group 4 |
---|
Period | period 6 |
---|
Block | d-block |
---|
Element category | Transeetion metal |
---|
Electron confeeguration | [Xe] 4f14 5d2 6s2 |
---|
Electrons per shell | 2, 8, 18, 32, 10, 2 |
---|
Pheesical properties |
---|
Phase at STP | solit |
---|
Meltin pynt | 2506 K (2233 °C, 4051 °F) |
---|
Bylin pynt | 4876 K (4603 °C, 8317 °F) |
---|
Density (near r.t.) | 13.31 g/cm3 |
---|
when liquid (at m.p.) | 12 g/cm3 |
---|
Heat o fusion | 27.2 kJ/mol |
---|
Heat o vapourisation | 571 kJ/mol |
---|
Molar heat capacity | 25.73 J/(mol·K) |
---|
Vapour pressur
P (Pa)
|
1
|
10
|
100
|
1 k
|
10 k
|
100 k
|
at T (K)
|
2689
|
2954
|
3277
|
3679
|
4194
|
4876
|
|
Atomic properties |
---|
Oxidation states | −2, +1, +2, +3, +4 (an amphoteric oxide) |
---|
Electronegativity | Pauling scale: 1.3 |
---|
Atomic radius | empirical: 159 pm |
---|
Covalent radius | 175±10 pm |
---|
Spectral lines o hafnium |
Ither properties |
---|
Naitural occurrence | primordial |
---|
Creestal structur | hexagonal close-packed (hcp) |
---|
Speed o soond thin rod | 3010 m/s (at 20 °C) |
---|
Thermal expansion | 5.9 µm/(m·K) (at 25 °C) |
---|
Thermal conductivity | 23.0 W/(m·K) |
---|
Electrical resistivity | 331 n Ω·m (at 20 °C) |
---|
Magnetic orderin | paramagnetic[2] |
---|
Young's modulus | 78 GPa |
---|
Shear modulus | 30 GPa |
---|
Bulk modulus | 110 GPa |
---|
Poisson ratio | 0.37 |
---|
Mohs haurdness | 5.5 |
---|
Vickers haurdness | 1760 MPa |
---|
Brinell haurdness | 1700 MPa |
---|
CAS Nummer | 7440-58-6 |
---|
History |
---|
Prediction | Dmitri Mendeleev (1869) |
---|
Diskivery | Dirk Coster an George de Hevesy (1922) |
---|
First isolation | Dirk Coster an George de Hevesy (1922) |
---|
Main isotopes o hafnium |
---|
|
Decay modes in parentheses are predictit, but hae nae yet been observed |
| references |