Tantalum
Tantalum is a chemical element with symbol Ta and atomic number 73. Previously known as tantalium, its name comes from Tantalus, an antihero from Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion-resistant.
Identity
- Atomic mass
- 180.948 u
- Category
- Transition metals
- Group
- 5
- Period
- 6
- Block
- d
- Oxidation States
- +5
- Phase (25 °C)
- Solid
- Appearance
- gray blue
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d3
- Short configuration
- [Xe] 4f14 5d3 6s2
- Electrons per shell
- 2, 8, 18, 32, 11, 2
- Electronegativity (Pauling)
- 1.50
- Electron affinity
- 31 kJ/mol
- 1st ionization energy
- 761 kJ/mol
- Ionization energies
- 761 · 1500 kJ/mol
Physical properties
- Melting point
- 3016.8 °C (3290 K)
- Boiling point
- 5457.9 °C (5731 K)
- Density
- 16.69 g/cm³
- Molar heat capacity
- 25.4 J/(mol·K)
Chemical behavior of tantalum
Tantalum has the electron configuration [Xe] 4f¹⁴ 5d³ 6s². Its predominant and practically exclusive oxidation state in solution is +5 (Ta⁵⁺), forming polymeric tantalum oxoanions and covalent bonds of great stability. It is a dense, hard, ductile transition metal of group 5, situated between niobium and dubnium. It shows an almost legendary chemical resistance to corrosion: below 150 °C it is totally immune to attack by almost all mineral acids (including aqua regia, nitric acid and sulfuric acid), protected by a self-limiting, compact surface film of tantalum pentoxide.
Reactivity
4 Ta + 5 O₂ → 2 Ta₂O₅
It combines slowly with oxygen, forming a passivating layer of tantalum pentoxide at room temperature; it burns in air above 300 °C.
Ta + 5 HF + HNO₃ → H₂[TaF₇] + ...
It is completely immune to pure acids except hydrofluoric acid, and to their mixtures with nitric acid, with which it forms soluble fluorotantalates.
2 Ta + 5 Cl₂ → 2 TaCl₅
It reacts with chlorine gas when heated to form sublimable tantalum pentachloride.
Ta + C → TaC
It reacts with carbon at high temperatures to produce cubic tantalum carbide, an ultra-hard ceramic.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Tantalum pentoxide | Ta₂O₅ | High-permittivity insulating dielectric film in tantalum electrolytic capacitors for mobile phones and motherboards |
| Tantalum carbide | TaC | Ultra-hard ceramic added to cemented tungsten carbides to prevent grain growth and improve cutting tools |
| Lithium tantalate | LiTaO₃ | Piezoelectric and electro-optic crystal used in surface acoustic wave (SAW) filters in mobile radio-frequency receivers |
| Tantalum pentachloride | TaCl₅ | White powder precursor for depositing thin tantalum films in microelectronics and chemical synthesis |
Electron shell distribution
View in the atom builderIsotopes
Natural tantalum consists of almost exclusively a single stable isotope, tantalum-181 (¹⁸¹Ta, with 108 neutrons and 99.988% abundance), along with a tiny fraction of the metastable nuclear isomer tantalum-180m (¹⁸⁰ᵐTa, 0.012%). ¹⁸⁰ᵐTa is the only metastable nuclear isomer that exists in nature as a primordial nuclide without its spontaneous decay ever having been observed (its experimental half-life exceeds 4.5 × 10¹⁶ years).
Occurrence and production
It is a scarce element in the Earth's crust (about 1 to 2 ppm). It appears in granitic pegmatites closely associated with niobium in isomorphic mineral series such as columbite-tantalite (known commercially as coltan). The largest commercial deposits are found in Australia, Brazil, Rwanda, the Democratic Republic of the Congo and Canada. Coltan ore is processed by digestion with hydrofluoric and sulfuric acid, separated from niobium by solvent extraction (MIBK) to precipitate potassium heptafluorotantalate (K₂TaF₇), which is then reduced with molten sodium metal.
History and origin of the name
It was discovered in 1802 by the Swedish chemist Anders Gustaf Ekeberg in tantalite mineral samples from Ytterby (Sweden) and Kimito (Finland). Observing that the new oxide was completely insoluble and incapable of absorbing acids, Ekeberg named it 'tantalum' after King Tantalus of Greek mythology, condemned to suffer eternal hunger and thirst while immersed in water that withdrew whenever he tried to drink it. For decades it was confused with niobium until Heinrich Rose demonstrated in 1844 that they were two different elements.
Applications and relevance of tantalum
Uses of the element
More than half of the world's tantalum is consumed by the electronics industry to make tiny tantalum electrolytic capacitors of enormous reliability and capacitance, present in smartphones, computers, satellites and medical electronics (such as pacemakers and defibrillators). Thanks to its absolute biocompatibility, it is used in bone implants, cranial plates, surgical meshes and orthopedic screws where bone tissue grows directly bonded to the metal.
Uses of its compounds
Tantalum pentoxide is the insulating coating of high-capacitance capacitors; lithium tantalate processes radio-frequency signals in mobile phone chips; and tantalum–nickel superalloys withstand extreme corrosive temperatures in jet engine turbine blades.
Health, safety and environment
Biological role
It plays no known biological role. It is one of the most biocompatible materials that exist: human tissue, blood and bone cells suffer no inflammation, rejection or immune response in its presence, allowing it to integrate into permanent prostheses without releasing toxic ions.
Safety
The bulk metal and its implants are completely inert and harmless. Fine tantalum dust particles can cause mechanical irritation to the eyes and respiratory tract during industrial polishing tasks, but they have no intrinsic systemic chemical toxicity.
Environment
The main impact associated with tantalum stems from illegal mining and armed conflicts tied to coltan extraction in Africa's Great Lakes region. Various international regulations, such as the US Dodd-Frank Act and European directives, require conflict-free mineral traceability to prevent the financing of armed groups.
Frequently asked questions about Tantalum
Why do mobile phones need tantalum in their circuits?
Smartphones need to store and release small amounts of electric charge very stably in a tiny space. Tantalum makes it possible to build minuscule capacitors with an extremely thin protective oxide layer that stores a large amount of energy in a fraction of a millimeter. Without these tantalum components, modern phones would have to be noticeably bulkier and less efficient.
What is the 'coltan' ore and why does its trade spark geopolitical controversies?
Coltan is the commercial shorthand for columbite-tantalite, a solid mineral solution of niobium oxides (formerly called columbium) and tantalum. It is the primary strategic ore from which tantalum is extracted to make consumer-electronics capacitors. In the Democratic Republic of the Congo, its artisanal extraction in remote mines has historically financed armed militias and smuggling networks, prompting international due-diligence laws on 'conflict minerals' across the technology supply chain.
Why do tantalum superalloys let jet engines withstand record temperatures?
In turbine blades of jet engines operating in gases above 1,100 °C, tantalum is added in proportions of 3% to 12% to single-crystal nickel superalloys. Tantalum preferentially dissolves in the precipitated gamma-prime phase (Ni₃Al), reinforcing its atomic bonds and preventing thermal dislocation slip. This confers remarkable resistance to continued plastic deformation ('creep'), extending the engines' flight time by thousands of hours.
How do lithium tantalate crystals help mobile phones?
Lithium tantalate is a crystal that can convert electrical signals into mechanical vibrations and vice versa. This property, called piezoelectricity, makes it possible to build components that filter specific radio frequencies and help separate the signals a phone needs to receive or transmit. These filters are important for wireless communications, although current devices may also use other materials and technologies.
What makes the tantalum-180m isotope so special?
Tantalum-180m is a form of tantalum whose nucleus remains in an excited energy state for an extraordinarily long time. Unlike many excited states, it has never been observed to decay routinely, making it a striking case of nuclear stability. Scientists study it to better understand how protons and neutrons arrange themselves inside atomic nuclei.
Why is tantalum used to make medical prostheses and implants?
Tantalum is one of the most body-compatible materials that exist. It causes no allergies and does not oxidize on contact with biological fluids. When made with a spongy or porous texture that mimics natural bone, human bone cells grow and anchor directly inside its pores, giving hip and knee implants a firm, permanent hold.
Why is tantalum resistant to aqua regia while gold and platinum dissolve in it?
Aqua regia dissolves gold and platinum by combining the oxidizing action of nitric acid with the chloride complexation of hydrochloric acid. In tantalum, however, dissolved oxygen and the oxidizing acid regenerate and thicken instantaneously a nanometer-thick, impermeable and chemically inert film of tantalum pentoxide (Ta₂O₅). This passivating layer completely blocks the acid's contact with the underlying metal, resisting chemical attack below 150 °C.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.