SymbolHf
Latin nameHafnium
Atomic number72
Period6
Element categoryTransition elements
Relative atomic mass178.49
GroupIV.B
Electronegativity
1.3
Oxidation numbers
4
Electron configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d2 6s2
Density [g/cm3]
13.3
State
Solid
Melting point [°C]
2227
Boiling point [°C]
4600
Atomic radius [pm]
208
Covalent radius [pm]
150
Thermal conductivity [W m-1K-1]
23
Heat capacity [J K-1g-1]
0.14
Discovery
1864
Hardness [Mohs scale]
5.5
Vickers hardness [MPa]
1760
Brinell hardness [MPa]
1700
Young's modulus [GPa]
78
Electrical conductivity [S m-1]
3.3 · 106
Shear modulus [GPa]
30
1.st ionization energy [eV]
6.8251
2.nd ionization energy [eV]
14.925
3.rd ionization energy [eV]
23.32
Stable isotopes
6
Unstable isotopes
15