Properties of Hafnium and Tantalum
Melting Point
2,150.00 °C
  
10
Hardness
  
  
Brinell Hardness
1,450.00 MPa
  
6
Vickers Hardness
1,520.00 MPa
  
5
Optical Properties
  
  
Refractive Index
Not Available
  
Not Available
  
Reflectivity
Not Available
  
Speed of Sound
3,010.00 m/s
  
27
3,400.00 m/s
  
22
Allotropes
No
  
No
  
α Allotropes
Not Available
  
Not Available
  
β Allotropes
Not Available
  
Not Available
  
γ Allotropes
Not Available
  
Not Available
  
Chemical Formula
Hf
  
Ta
  
Isotopes
  
  
Electronegativity
  
  
Pauling Electronegativity
Sanderson Electronegativity
Not Available
  
Not Available
  
Allred Rochow Electronegativity
Mulliken-Jaffe Electronegativity
Not Available
  
Not Available
  
Electropositivity
  
  
Pauling Electropositivity
Ionization Energies
  
  
1st Energy Level
658.50 kJ/mol
  
40
761.00 kJ/mol
  
18
2nd Energy Level
1,440.00 kJ/mol
  
99+
1,500.00 kJ/mol
  
40
3rd Energy Level
2,250.00 kJ/mol
  
99+
Not Available
  
Electrochemical Equivalent
1.66 g/amp-hr
  
99+
1.35 g/amp-hr
  
99+
Other Chemical Properties
Density
  
  
Density At Room Temperature
13.31 g/cm3
  
26
16.69 g/cm3
  
18
Density When Liquid (at m.p.)
12.00 g/cm3
  
12
Vapor Pressure
  
  
Vapor Pressure at 1000 K
Not Available
  
Not Available
  
Tensile Strength
Not Available
  
Viscosity
Not Available
  
Not Available
  
Elasticity properties
  
  
Other Mechanical Properties
Symbol
Hf
  
Ta
  
Period Number
6
  
6
  
Atomic Volume
13.60 cm3/mol
  
38
10.90 cm3/mol
  
99+
Electron Configuration
[Xe] 4f14 5d2 6s2
  
[Xe] 4f14 5d3 6s2
  
Valence Electron Potential
81.00 (-eV)
  
16
110.00 (-eV)
  
7
Atom
  
  
Crystal Lattice
BCC-Crystal-Structure-.jpg#100
  
BCC-Crystal-Structure-.jpg#100
  
Radius of an Atom
  
  
Lattice Angles
π/2, π/2, 2 π/3
  
π/2, π/2, π/2
  
Lattice C/A Ratio
Not Available
  
Adjacent Atomic Numbers
  
  
Electrical Properties
  
  
Resistivity
331.00 nΩ·m
  
14
131.00 nΩ·m
  
25
Electrical Conductivity
0.03 106/cm Ω
  
39
0.08 106/cm Ω
  
27
Electron Affinity
0.00 kJ/mol
  
40
31.00 kJ/mol
  
29
Magnetic Characteristics
  
  
Permeability
Not Available
  
Not Available
  
Susceptibility
Not Available
  
Not Available
  
Specific Heat
0.14 J/(kg K)
  
37
0.14 J/(kg K)
  
37
Thermal Conductivity
23.00 W/m·K
  
99+
57.50 W/m·K
  
27
Critical Temperature
Not Available
  
Not Available
  
Molar Heat Capacity
25.73 J/mol·K
  
36
25.36 J/mol·K
  
99+
Thermal Expansion
5.90 µm/(m·K)
  
99+
6.30 µm/(m·K)
  
99+
Standard Molar Entropy
43.60 J/mol.K
  
34
41.50 J/mol.K
  
37
Enthalpy
  
  
Enthalpy of Vaporization
661.10 kJ/mol
  
5
753.10 kJ/mol
  
2
Enthalpy of Fusion
25.10 kJ/mol
  
8
31.40 kJ/mol
  
3
Enthalpy of Atomization
703.00 kJ/mol
  
5
782.00 kJ/mol
  
3