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Reference


Hafnium
Chemical Properties & Compounds



Symbol Atomic Number Atomic Weight Melting Point Boiling Point Phase Density Classification
Hf 72 178.49 2233 °C 4603 °C Solid 13.31 g/cm3 Metal


72 lutetium ← hafnium → tantalum
Zr
↑
Hf
↓
Rf
General
Name, Symbol, Number hafnium, Hf, 72
Chemical series transition metals
Group, Period, Block 4, 6, d
Appearance grey steel
Standard atomic weight 178.49(2)  g·mol−1
Electron configuration [Xe] 4f14 5d2 6s2
Electrons per shell 2, 8, 18, 32, 10, 2
Physical properties
Phase solid
Density (near r.t.) 13.31  g·cm−3
Liquid density at m.p. 12  g·cm−3
Melting point 2506 K
(2233 °C, 4051 °F)
Boiling point 4876 K
(4603 °C, 8317 °F)
Heat of fusion 27.2  kJ·mol−1
Heat of vaporization 571  kJ·mol−1
Heat capacity (25 °C) 25.73  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 2689 2954 3277 3679 4194 4876
Atomic properties
Crystal structure hexagonal
Oxidation states 4
(amphoteric oxide)
Electronegativity 1.3 (scale Pauling)
Ionization energies
(more)		 1st:  658.5  kJ·mol−1
2nd:  1440  kJ·mol−1
3rd:  2250  kJ·mol−1
Atomic radius 155  pm
Atomic radius (calc.) 208  pm
Covalent radius 150  pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (20 °C) 331 n Ω·m
Thermal conductivity (300 K) 23.0  W·m−1·K−1
Thermal expansion (25 °C) 5.9  µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 3010 m/s
Young's modulus 78  GPa
Shear modulus 30  GPa
Bulk modulus 110  GPa
Poisson ratio 0.37
Mohs hardness 5.5
Vickers hardness 1760  MPa
Brinell hardness 1700  MPa
CAS registry number 7440-58-6
Selected isotopes
Main article: Isotopes of hafnium
iso NA half-life DM DE (MeV) DP
172Hf syn 1.87 y ε 0.350 172Lu
174Hf 0.162% 2×1015 y α 2.495 170Yb
176Hf 5.206% Hf is stable with 104 neutrons
177Hf 18.606% Hf is stable with 105 neutrons
178Hf 27.297% Hf is stable with 106 neutrons
178m2Hf syn 31 y IT 2.446 178Hf
179Hf 13.629% Hf is stable with 107 neutrons
180Hf 35.1% Hf is stable with 108 neutrons
182Hf syn 9×106 y β 0.373 182Ta
References
Hafnium Compounds

Source: Wikipedia article Hafnium


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