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Element Fact
Iridium is the most corrosion-resistant metal known. Together with platinum, it is used to make the international prototype of the kilogram, which is the standard definition for the unit of mass.

Tantalum, Ta

tantalum sample

Atomic number: 73
Atomic mass: 180.9479(1)
Natural abundance: 1.7 ppm
180Ta (179.947466) - 0.012%
181Hf (180.947996) - 99.988%

History and Production

From Greek mythology Tantalos, the father of Niobe. In 1802 A.G. Ekeberg identified a new element from some Finnish minerals. He named it tantalum due to difficulty of dissolving the mineral in acids. It was once thought that niobium was the same element as that of tantalum. This was later clarified by H. Rose in 1844 when he examined a columbite mineral sample that the two metals are distinct. The pure sample of tantalum was first prepared by W. von Bolton in 1907 by reduction of fluorotantallate with sodium metal. It is obtained as a byproduct in the extraction of tin. Tantalum can be recovered using Rose's method. It can also be obtained by electrolysis of molten potassium fluorotantallate. Tantalum is used in corrosion-resistant applications such as liner in chemical plants and nuclear reactors, surgical equipment in bone repair and internal suturing. It is also used in electronic industry for making capacitors.

Physical Data

Tantalum is a gray and very hard metal. It has a strong resistance to most chemical attacks at low temperatures. Tantalum occurs invariably with niobium in minerals such as columbite, with a natural abundance of about 1.7 ppm.

Interatomic distance: 286 pm
Melting point: 3017C
Boiling point: 5458C
Thermal conductivity/Wm-1K-1: 57.5 (27C)
Density/kgm-3: 16654 (20C), 15000 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 782.0 kJ/mol
Gibbs free energy of formation: 739.3 kJ/mol
Entropy: 185.2 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Xe] 4f14 5d3 6s2
Term symbol: 4F3/2
Electron affinity: 31.0683 kJ/mol   Electronegativity (Pauline): 1.5
Ionization energy (first, second, third): 728.426, -, - kJ/mol

Chemical properties

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