Atomic number 73

Tantalum

Ta
+ phase
− phase

Shells Orbitals 4f 5d 6s

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73 electrons in 6 shells: 2, 8, 18, 32, 11, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Transition metal
Period: 6
Group: 5
Block: d
Standard atomic weight: 180.95(1) Da
Electron configuration: [Xe] 4f¹⁴ 5d³ 6s²
Phase at 25 °C: solid
Melting point: 3017 °C
Boiling point: 5458 °C
Density: 16.4 g/cm³
Electronegativity (Pauling): 1.5
Discovered: 1802, Ekeberg

Neighbours in the table

Hf W

For 64 years after its discovery, chemists could not agree that tantalum was an element of its own. The Swedish chemist Ekeberg reported it in 1802, in minerals from Ytterby, Jefferson Lab’s text on PubChem’s record says. Many took the new metal for niobium, which Jefferson Lab calls chemically similar to it. Heinrich Rose took the first step, in Jefferson Lab’s account of niobium. Marignac ended the doubt in 1866: he proved, Los Alamos says, that niobic and tantalic acids were different compounds. In Los Alamos’s telling of the myth, Tantalos was Niobe’s father.

Beyond the xenon core and a full 4f subshell, tantalum has three 5d electrons and a 6s pair, written [Xe] 4f¹⁴ 5d³ 6s². Those five valence electrons place it in group 5. Niobium, directly above, breaks the expected pattern with 5s¹ 4d⁴, and OpenStax says no simple method predicts such exceptions. Jefferson Lab gives only +5 as tantalum’s oxidation state, the charge each atom would carry if its bonds were fully ionic. Los Alamos lists states from 5 down to −3.

The metal is grey, dense and very hard, Los Alamos says, yet pure samples are ductile enough to draw into fine wire. Los Alamos dates the first fairly pure, ductile tantalum to von Bolton in 1903, while Jefferson Lab gives 1907.

Where it is found

Jefferson Lab’s estimates on PubChem’s record put tantalum at 2.0 milligrams per kilogram of crust and 2 × 10⁻⁶ milligrams per litre of seawater. Jefferson Lab names its chief sources as columbite, written (Fe,Mn,Mg)(Nb,Ta)₂O₆, and tantalite, (Fe,Mn)(Ta,Nb)₂O₆, formulas that bracket the two metals together, plus a third mineral, euxenite. Los Alamos calls the separation of tantalum from niobium a matter of several complicated steps.

The US Geological Survey estimates 2024 world mine output at about 2,100 metric tons of tantalum. Congo (Kinshasa) supplied 880 tons, Nigeria 390 and Rwanda 350, with Brazil, China, Mozambique and Australia behind them. The United States has mined none since 1959. Its identified deposits hold about 55,000 tons, but they are low grade and mostly not recoverable at a profit.

Recycled tantalum comes mostly from electronic-component manufacturing scrap and from cemented-carbide and superalloy scrap, the US Geological Survey says. It adds that recycling may meet up to 30 per cent of what US primary processors consume. Los Alamos names three routes to the metal itself: electrolysis of molten potassium fluorotantalate, reduction of the same salt with sodium, and reaction of tantalum carbide with tantalum oxide.

Why it matters

Electrolytic capacitors and vacuum furnace parts together take about 60 per cent of tantalum, by Los Alamos’s estimate. In a capacitor the working layer is tantalum pentoxide, Ta₂O₅, a dielectric, an insulator that separates the charged plates. Los Alamos describes tantalum oxide films as stable, with good dielectric properties.

US apparent consumption, essentially imports minus exports since nothing is mined there, reached an estimated 770 metric tons in 2024. That was 75 per cent above 2023, which the survey says 2022 stockpiling held down. It credits the 12 per cent rise in 2024 imports mainly to recovering demand from consumer electronics and data centres. It expects a growing US chip industry to need more tantalum for capacitors and chip-making metal films. Aluminium, ceramics and niobium can replace it in capacitors, though performance may suffer or costs rise, the survey says.

Surgeons use tantalum because body fluids leave it untouched and it does not irritate tissue, in Los Alamos’s account. Jefferson Lab lists sutures, artificial joints and cranial plates. A short-lived isotope serves medicine as well: IUPAC’s table on PubChem’s record names tantalum-178 for blood-pool imaging. The Atomic Mass Data Center’s figures there list a 9.31-minute isomer, an excited nuclear state, and a ground state lasting 2.36 hours.

Properties

Properties of tantalum Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	73
Standard atomic weight	180.95(1) Da	Da	IUPAC/CIAAW 2024
Melting point	3017 °C	°C	Los Alamos: 3017 °C
Boiling point	5458 °C	°C	Los Alamos: 5458 °C
Density	16.4 g/cm³	g/cm³
Electronegativity (Pauling)	1.5
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d³
Phase at 25 °C	solid

Safety

Solid tantalum, whether a cranial plate, a capacitor or a wire, is essentially harmless: Los Alamos calls the metal nonirritating and unaffected by body fluids. The cautions in PubChem’s safety summary centre on fine powder and dust, which can ignite by itself in air and irritates the eyes, skin and airways. Some company reports to the European Chemicals Agency also class the substance as self-heating in large quantities. That summary and the tantalum dust card from NIOSH, the US National Institute for Occupational Safety and Health, are the references for workplaces handling the powder.

Questions

Why is tantalum named after Tantalus?

The name refers to acids, according to CIAAW, IUPAC's atomic-weights commission, in PubChem's record. Set among them, the metal takes none of them up, like Tantalus in Greek myth, chin-deep in water that drew back whenever he tried to drink. The immunity has limits: Los Alamos lists hydrofluoric acid, acid solutions holding fluoride ions and free sulfur trioxide as attackers, and says the hot metal grows far more reactive.

Is natural tantalum radioactive?

Almost all of it is tantalum-181, stable in the Atomic Mass Data Center (AMDC) table on PubChem's record, and about 99.988 per cent of the atoms by CIAAW's figures. Mass 180 makes up the other 0.012 per cent. The same table gives the ground state of tantalum-180 a half-life of 8.154 hours, and an isomer, an excited state of that nucleus, a half-life beyond 4.5 × 10¹⁶ years. Jefferson Lab counts one stable isotope, Los Alamos two natural ones.

Is tantalum toxic?

Of 455 company reports to the European Chemicals Agency, 44 per cent find no hazard under the UN's Globally Harmonized System. Most others class it as a flammable solid, some as self-heating in large quantities. Japan's 2006 classification in the same file lists harm if swallowed, eye irritation and respiratory irritation; its 2015 revision keeps only respiratory irritation. NIOSH, the US National Institute for Occupational Safety and Health, notes that the powder can ignite by itself in air.

Why is tantalum used instead of platinum?

Cost, on Jefferson Lab's account in PubChem's record: tantalum has a high melting point and often stands in for platinum, the dearer metal. Below 150 °C almost nothing attacks it, Los Alamos says, and chemical process equipment is among its uses. OpenStax adds a trait the two share: with iron and tungsten, they are the main metals that form no amalgam, an alloy with mercury.