Properties of Tantalum and Hafnium
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
3,400.00 m/s
  
22
3,010.00 m/s
  
27
Allotropes
No
  
No
  
α Allotropes
Not Available
  
Not Available
  
β Allotropes
Not Available
  
Not Available
  
γ Allotropes
Not Available
  
Not Available
  
Chemical Formula
Ta
  
Hf
  
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
761.00 kJ/mol
  
18
658.50 kJ/mol
  
40
2nd Energy Level
1,500.00 kJ/mol
  
40
1,440.00 kJ/mol
  
99+
3rd Energy Level
Not Available
  
2,250.00 kJ/mol
  
99+
Electrochemical Equivalent
1.35 g/amp-hr
  
99+
1.66 g/amp-hr
  
99+
Other Chemical Properties
Density
  
  
Density At Room Temperature
16.69 g/cm3
  
18
13.31 g/cm3
  
26
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
Ta
  
Hf
  
Period Number
6
  
6
  
Atomic Volume
10.90 cm3/mol
  
99+
13.60 cm3/mol
  
38
Electron Configuration
[Xe] 4f14 5d3 6s2
  
[Xe] 4f14 5d2 6s2
  
Valence Electron Potential
110.00 (-eV)
  
7
81.00 (-eV)
  
16
Atom
  
  
Crystal Lattice
BCC-Crystal-Structure-.jpg#100
  
BCC-Crystal-Structure-.jpg#100
  
Radius of an Atom
  
  
Lattice Angles
π/2, π/2, π/2
  
π/2, π/2, 2 π/3
  
Lattice C/A Ratio
Not Available
  
Adjacent Atomic Numbers
  
  
Electrical Properties
  
  
Resistivity
131.00 nΩ·m
  
25
331.00 nΩ·m
  
14
Electrical Conductivity
0.08 106/cm Ω
  
27
0.03 106/cm Ω
  
39
Electron Affinity
31.00 kJ/mol
  
29
0.00 kJ/mol
  
40
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
57.50 W/m·K
  
27
23.00 W/m·K
  
99+
Critical Temperature
Not Available
  
Not Available
  
Molar Heat Capacity
25.36 J/mol·K
  
99+
25.73 J/mol·K
  
36
Thermal Expansion
6.30 µm/(m·K)
  
99+
5.90 µm/(m·K)
  
99+
Standard Molar Entropy
41.50 J/mol.K
  
37
43.60 J/mol.K
  
34
Enthalpy
  
  
Enthalpy of Vaporization
753.10 kJ/mol
  
2
661.10 kJ/mol
  
5
Enthalpy of Fusion
31.40 kJ/mol
  
3
25.10 kJ/mol
  
8
Enthalpy of Atomization
782.00 kJ/mol
  
3
703.00 kJ/mol
  
5