Tantalum (Ta)

Stable isotopes of tantalum available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Ta-180  73  107  179.947466 0.012%  0.26-5.70% Oxide
Ta-181  73  108  180.947996 99.988%  99.99%  Oxide

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Tantalum was discovered in 1802 by Anders Ekeberg. Its name derives from the Greek name Tantalos, meaning “father of Niobe” (tantalum is closely related to niobium in the periodic table).

A gray, heavy, very hard metal, tantalum is also malleable and ductile and has a body-centered cubic lattice structure. It is soluble in fused alkalis and hydrofluoric acid, and insoluble in water, alcohol and all acids, except hydrofluoric and fuming sulfuric acids. Its aqueous solution chemistry is that of its pentavalent ion, Ta5+. The metal is attacked by hydrofluoric acid below 150 ºC. It also is dissolved by hot fuming sulfuric acid. It reacts with fluorine and chlorine on heating. The metal is immune to dilute aqueous alkalis but is attacked slowly by concentrated fused alkalis. Tantalum forms alloys with several metals: tantalum and its alloys have high melting points, high strength and ductility, and show excellent resistance to chemical attack. Tantalum carbide graphite composite is one of the hardest substances ever made; it has a melting point of 6700 ºC.

The pure metal is ductile and can be drawn into fine wire, which is used as a filament for evaporating aluminum and other metals. Tantalum and its alloys are used to build reactors, vessels, and crucibles for preparing and carrying out reactions involving many reactive intermediates. The metal and its alloys also are used to construct furnace parts, electrolytic capacitors, aircraft and missile parts, chemical process equipment, and nuclear reactors. Since it is nonreactive to body fluids and a nonirritant to body tissues, tantalum is used in making surgical appliances. Plate and sheet tantalum are applied in bone repair; foil and wire in nerve repair; and plate, gauge and sheet in the repair of abdominal muscle. Tantalum oxide is used to produce optical glasses of high refractive index. The oxide film on the metal makes it a rectifier for converting alternating current to direct current.

Properties of Tantalum

Name Tantalum 
Symbol Ta 
Atomic number 73 
Atomic weight 180.95 
Standard state Solid at 298 ºK 
CAS Registry ID 7440-25-7 
Group in periodic table
Group name None 
Period in periodic table
Block in periodic table d-block 
Color Gray blue 
Classification Metallic 
Melting point 2996 °C
Boiling point 5425 °C
Vaporization point 5458 ºC
Thermal conductivity 57.5 W/(m·K) at 298.2 °K
Electrical resistivity 12.45 µΩ·cm at 0 °C 
Electronegativity 1.5 
Specific heat 0.14 kJ/kg K
Heat of vaporization 735 kJ·mol-1
Heat of fusion 36 kJ·mol-1
Density of liquid 15 g/cm3 
Density of solid 16.65 g/cm3
Electron configuration [Xe]4f145d36s2 
Atomic radius 1.46 Å 
Ionic radius Ta5+: 0.64 Å (coordination number 6)
Oxidation state  +5

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