Tantalum – facts and properties
- Symbol
- Ta
- Atomic number
- 73
- Atomic mass
- 180.948 u
- Period
- 6
- Group
- 5
- Category
- transition metal
- Electron configuration
- [Xe] 4f¹⁴ 5d³ 6s²
- Electronegativity
- 1.5
- Atomic radius
- 209 pm
- Valence electrons
- 5
- State at standard conditions
- solid
- Melting point
- 3017 °C
- Boiling point
- 5458 °C
- Density
- 16.4 g/cm³
- Discovered
- 1802
Tantalum is a blue-grey, dense and tough transition metal with atomic number 73. It resists almost every acid, and its oxide is the basis of tiny capacitors found in smartphones and laptops. The name recalls Tantalus, a figure from Greek myth, because its oxide took up nothing from acids, just as Tantalus could not drink the water around him. The ore coltan became widely known through mining in conflict regions.
Position in the periodic table
Occurrence and extraction
Tantalum is not found in nature as a pure metal. Its main ore is tantalite, an iron-manganese mineral holding tantalum, which merges gradually into the niobium-rich columbite. The mixture is known in trade as coltan. Important producing countries include the Democratic Republic of the Congo, Rwanda, Brazil and Australia.
Mining coltan has a troubled reputation. In the east of Congo some of it happens in small, poorly secured pits, and the trade has helped to fund armed groups. Tantalum is therefore counted among the so-called conflict minerals, as are tin, tungsten and gold. A law in the United States and a regulation of the European Union require certain companies to carry out due diligence on their supply chains so that raw materials do not pay for violence.
The element was discovered in 1802 by the Swedish chemist Anders Gustaf Ekeberg in minerals from Sweden and Finland. He chose the name because the oxide would not dissolve in acids even when surrounded by them, which reminded him of Tantalus, who stood in water and could not drink. Soon afterwards tantalum and niobium were taken for the same element, since the two are chemically almost impossible to tell apart. Only around the middle of the nineteenth century did Heinrich Rose show that there were two.
Properties and reactions
Tantalum is in period 6 and group 5, below niobium, which belongs to period 5. Its electron configuration is [Xe] 4f¹⁴ 5d³ 6s² and its electronegativity is 1.5. The metal has a density of 16.4 g/cm³, melts at 3017 °C and boils at 5458 °C, so it is more than twice as heavy as steel. Niobium and tantalum have atoms of almost the same size, which explains why they behave so alike. The cause is the lanthanide contraction: along the lanthanides the atoms shrink, and this cancels out the growth that an extra electron shell would bring.
Tantalum is very ductile and can be drawn into fine wire. In compounds it mostly has oxidation number plus five. In air the metal becomes covered with a dense, colourless film of tantalum pentoxide, Ta₂O₅. It protects so well that at room temperature even hydrochloric acid, nitric acid and aqua regia do nothing. Tantalum is attacked by hydrofluoric acid and by hot, strong alkalis. At high temperature it absorbs oxygen, nitrogen and hydrogen and becomes brittle.
The oxide film can be built up electrically. The oxide is an excellent insulator with a high dielectric constant. It is exactly this combination that makes tantalum so valuable for capacitors.
Uses in everyday life and technology
Most tantalum goes into electronics. A tantalum capacitor is made from porous tantalum powder that is sintered into a pellet and coated with tantalum oxide. The vast surface and the wafer-thin insulating layer store a lot of charge in very little space. Such parts are reliable and long-lived, which is why they sit in smartphones, laptops, cameras, car electronics and hearing aids, as well as in pacemakers.
Tantalum is also valued in chemical engineering. Vessels, heat exchangers and linings made of tantalum withstand hot, aggressive acids where even stainless steel would fail.
Tantalum is also important in medicine. The body tolerates the metal very well, and it shows up clearly on X-ray images. It is made into skull plates, staples, markers and porous parts of joint implants into which bone can grow. Further uses are superalloys for jet engines, hard metals containing tantalum carbide and coating material for semiconductor manufacturing.
Quick question
What is the atomic number of tantalum (Ta)?
FAQ
Why is tantalum called tantalum?
The name comes from Tantalus, a king of Greek myth who, as a punishment, stood chin-deep in water and could never drink. Ekeberg saw this as a picture of the oxide, which would not dissolve in acids.
What is coltan?
Coltan is a trade name for a mixed ore of columbite and tantalite, from which niobium and above all tantalum are obtained. Because part of it comes from conflict regions, manufacturers increasingly rely on checked supply chains and recycling.
What is the difference between tantalum and niobium?
Both sit in the same group, have atoms of almost equal size and occur in the same ore. Tantalum is nearly twice as dense and melts higher. It dominates in capacitors, whereas niobium is needed mainly in steel and superconductors.