Tantalum
[Xe] 4f¹⁴ 5d³ 6s² · 2 · 8 · 18 · 32 · 11 · 2
A metal that is nearly impossible to dissolve and that the body accepts without any reaction at all. Tantalum's oxide film is so thin and so reliable that it yields capacitors of record capacitance per unit volume.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 73
- Atomic mass
- 180.948 а.е.м.
- Electron configuration
- [Xe] 4f¹⁴ 5d³ 6s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 11 · 2
- Block
- d-block
- Group
- Vanadium group
- Period
- 6
- Electronegativity (Pauling)
- 1.5
- Electronegativity (Allen)
- 1.34
- Atomic radius
- 200 pm
- Covalent radius
- 170 pm
- Van der Waals radius
- 217 pm
- Ionisation energy 1
- 761 kJ/mol
- Ionisation energy 2
- 1 500 kJ/mol
- Electron affinity
- 31 kJ/mol
- Common oxidation states
- +5
- Oxidation states
- -3, -1, +1, +2, +3, +4, +5
Physical properties
- State at 25 °C
- solid
- Density
- 16.69 g/cm³
- Melting point
- 3 290 K · 3 016.9 °C
- Boiling point
- 5 731 K · 5 457.9 °C
- Speed of sound
- 3 400 m/s
Thermal properties
- Heat of fusion
- 36.57 kJ/mol
- Heat of vaporisation
- 753 kJ/mol
- Specific heat capacity
- 0.14 J/(g·K)
- Thermal conductivity
- 57.5 W/(m·K)
Mechanical properties
- Young's modulus
- 186 GPa
- Shear modulus
- 69 GPa
- Bulk modulus
- 200 GPa
- Poisson ratio
- 0.34
- Mohs hardness
- 6.5
- Brinell hardness
- 800 MPa
Electrical and magnetic properties
- Electrical resistivity
- 131 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- 4.47 K
Crystal structure
- Crystal structure
- body-centred cubic (bcc)
- Lattice constants
- a = 330.13 pm
Abundance
- In the crust
- 2 mg/kg
- In the ocean
- 2·10⁻⁶ mg/L
- In the universe
- 0.008 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 180Ta | 0.012 % | stable | — |
| 181Ta | 99.988 % | stable | — |
Tantalum-180m is the rarest natural nuclide in the universe and the only natural nuclear isomer; its decay has never been observed.
Discovery
- Year of discovery
- 1802
- Discovered by
- Anders Gustaf Ekeberg
- Where
- Sweden
- Origin of the name
- after Tantalus: the oxide would not absorb acid, as Tantalus could not drink
History
Ekeberg discovered tantalum in 1802 and named it after Tantalus, who stood in water he could not drink: the oxide would not dissolve in any acid. For half a century tantalum was confused with niobium.
Where it occurs
2 mg/kg of the crust. The main ore is coltan, columbite-tantalite. A significant share is mined in Central Africa, which is what made it a conflict mineral.
How it is produced
From coltan via fluoride complexes separated by extraction, then sodium reduction. An increasing share comes from recycled electronics.
Role in living things
No biological role, but tantalum is exceptionally biocompatible: cranial plates have been made of it since the 1940s.
Safety
The metal is harmless. The dust irritates the airways.
Uses
- Tantalum capacitors: the highest capacitance per volume, hence one in every smartphone
- Medical implants and surgical mesh — tantalum is bioinert
- Chemical plant for the most aggressive media
- Tantalum carbide in cemented carbides and refractory materials
Curiosities
- Tantalum-180m is the only natural isomer and the rarest stable nuclide: 0.012 % of natural tantalum.
- Tantalum capacitors sit in every smartphone, and coltan's place on the conflict minerals list follows from that.
- Tantalum resists aqua regia at room temperature, as gold and platinum do.
- The name recalls the myth: the oxide stood in acid and could not drink.