Tantalum
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Background
Tantalum is a hard, grayish-blue, metallic element. Its atomic number is 73 and its symbol is Ta. It has a very high melting point (2,996°C). This melting point is exceeded only by that of carbon, tungsten, and rhenium. Tantalum is remarkably resistant to attack by air, water and most acids.
Tantalum was discovered in 1802 by the Swedish scientist Anders Ekeberg. Commercial use of tantalum began in 1903 with the production of tantalum wire.
Name
| Previous Element: Hafnium Tantalum Next Element: Tungsten |
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| Physical Properties | ||
|---|---|---|
| Color | gray | |
| Phase at Room Temp. | solid | |
| Density (g/cm3) | 16.65 | |
| Hardness (Mohs) | --- | |
| Melting Point (K) | 3269.2 | |
| Boiling Point (K) | 5807 | |
| Heat of Fusion (kJ/mol) | 31.38 | |
| Heat of Vaporization (kJ/mol) | 753 | |
| Heat of Atomization (kJ/mol) | 782 | |
| Thermal Conductivity (J/m sec K) | 57.5 | |
| Electrical Conductivity (1/mohm cm) | 80.321 | |
| Pure Cost ($/100g) | $120.00 | |
| Bulk Cost ($/100g) | --- | |
| Source | Tantalite (oxide) | |
| Atomic Properties | ||
| Electron Configuration | [Xe]6s24f145d3 | |
| Number of Isotopes | 47 (2 natural) | |
| Electron Affinity (kJ/mol) | 0 | |
| First Ionization Energy (kJ/mol) | 680 | |
| Second Ionization Energy (kJ/mol) | 1440 | |
| Third Ionization Energy (kJ/mol) | 2250 | |
| Electronegativity | 31.1 | |
| Polarizability (Å3) | 13.1 | |
| Atomic Weight | 180.95 | |
| Atomic Volume (cm3/mol) | 10.9 | |
| Ionic Radius2- (pm) | --- | |
| Ionic Radius1- (pm) | --- | |
| Atomic Radius (pm) | 146 | |
| Ionic Radius1+ (pm) | --- | |
| Ionic Radius2+ (pm) | --- | |
| Ionic Radius3+ (pm) | 86 | |
| Common Oxidation Numbers | +5 | |
| Other Oxid. Numbers | -1, +2, +3 +4 | |
| Abundance | ||
| In Solar System (log) | -1.684 | |
| In Earth's Crust (mg/kg) | 2.0x100 | |
| In Earth's Ocean (mg/L) | 2.0x10-6 | |
| In Human Body (%) | 0% | |
| Regulatory / Health | ||
| CAS Number | 7440-25-7 | |
| OSHA Permissible Exposure Limit (PEL) | TWA: 5 mg/m3 | |
| OSHA PEL Vacated 1989 | TWA: 5 mg/m3 | |
| NIOSH Recommended Exposure Limit (REL) | TWA: 5 mg/m3 STEL: 10 mg/m3 IDLH: 2500 mg/m3 | |
Tantalum is mostly found with the element niobium. The two elements are so similar that they are very difficult to isolate from one another. Tantalum was named after the Greek god, Tantalus. Niobium, discovered before tantalum (1801), was named after the daughter of Tantalus, Niobe.
Sources
Tantalum is recovered from ore minerals such as columbite and tantalite. The United States has no high-grade tantalum ores. In fact, no significant tantalum ores have been mined in the U.S. since 1959.
About 20% of the tantalum used in the United States comes from recycling. The rest must be imported. Recent major sources for tantalum imports were Australia, Kazakhstan, Canada, China, Thailand, and others.
Uses
The electronics industry uses most of the tantalum consumed to make electronic components (tantalum capacitors). Since tantalum is so resistant to corrosion, it is used to make surgical instruments and medical equipment such as rods to attach to broken bones, skull plates, and wire meshes to help repair nerves and muscles.
Because it has such a very high melting point, it is alloyed (that is, mixed with) other metals to create alloys that are needed for very high temperature applications. Tantalum is also used in camera lenses.
Substitutes and Alternative Sources
Columbium can be used in place of tantalum to make carbides. Columbium, hafnium, iridium, molybdenum, rhenium and tungsten can be used for high-temperature situations. Aluminum and ceramics can be used in place of tantalum in electronic capacitors. The problem is, however, that most of these substitutes are not as effective as tantalum in some of these applications.
Further Reading
- Common Minerals and Their Uses, Mineral Information Institute.
- More than 170 Mineral Photographs, Mineral Information Institute.
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