Atomic number 41

Niobium

Nb
+ phase
− phase

Shells Orbitals 4d 5s

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41 electrons in 5 shells: 2, 8, 18, 12, 1.

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

Category: Transition metal
Period: 5
Group: 5
Block: d
Standard atomic weight: 92.906(1) Da
Electron configuration: [Kr] 4d⁴ 5s¹
Phase at 25 °C: solid
Melting point: 2477 °C
Boiling point: 4744 °C
Density: 8.57 g/cm³
Electronegativity (Pauling): 1.6
Discovered: 1801, Charles Hatchett

Neighbours in the table

Zr Mo

A mineral sample from colonial Connecticut carried niobium to London. John Winthrop the Younger, the colony’s first governor, found the mineral around 1734 and sent it to the British Museum, Jefferson Lab’s account says. Charles Hatchett analysed this columbite in 1801, saw an unknown element and called it columbium, though he could not isolate the metal. Heinrich Rose renamed it in 1844 by Jefferson Lab’s date, or 1846 by CIAAW’s, after Niobe, daughter of Tantalus. CIAAW says he picked the name because the element was so hard to tell apart from tantalum.

Niobium carries 41 electrons, 2, 8, 18, 12 and 1 across its shells, written [Kr] 4d⁴ 5s¹. An element’s valence, its combining power, depends largely on its outer-shell electrons, Chem1 notes. Its d electrons allow several valences, Chem1 adds. Los Alamos lists its oxidation states, bookkeeping charges as if all bonds were ionic, as +5, +4, +3, +2, +1, −1 and −3; Jefferson Lab gives +5 and +3.

Los Alamos describes the metal as shiny, white and ductile. Its Pauling electronegativity, its pull on electrons shared in a bond, is 1.6, below the rough 2.2 mark that Chem1 links with metallic character. Metal ions bathed in a mobile electron fluid bond equally in every direction, which Chem1 gives as the reason metals draw and bend so well.

Where it is found

Jefferson Lab estimates 20 milligrams of niobium per kilogram of crust and 1 × 10⁻⁵ milligrams in a litre of seawater. Its main ores are pyrochlore, (Ca,Na)₂Nb₂O₆(O,OH,F), and the mineral Hatchett studied, columbite, (Fe,Mn,Mg)(Nb,Ta)₂O₆. Most identified resources are pyrochlore in carbonatite, which the US Geological Survey defines as igneous rock more than 50 per cent carbonate minerals by volume.

Brazil produced about 92 per cent of world niobium in 2024 and Canada about 7 per cent, by the survey’s estimates. Brazil mined 100,000 of the world’s roughly 110,000 metric tons, and it holds 16 million of the more than 17 million tons in world reserves. No significant US mine output has been reported since 1959; a Nebraska project would become the country’s only niobium mine and primary processing plant.

Christian Wilhelm Blomstrand first obtained the metal, in 1864 according to Los Alamos and Jefferson Lab, or 1846 according to CIAAW. Los Alamos says he heated the chloride under hydrogen to reduce it. Niobium always occurs with tantalum, and Jefferson Lab blames confusion between them on how alike the two metals are and how hard they are to isolate.

Why it matters

Steel takes most of the niobium the United States uses: about 77 per cent in 2024, with superalloys, metals made for high-temperature service, at about 21 per cent. The steel industry buys it mostly as ferroniobium, and net import reliance stood at 100 per cent, by the survey’s figures. Los Alamos says niobium raises the strength of steel and that niobium alloy steels often go into pipelines. It also goes into arc-welding rods for stabilised grades of stainless steel.

Beyond steel, thousands of pounds of niobium went into airframe systems like those of the Gemini space programme, according to Los Alamos. The survey notes that aerospace specialty steels and alloys need high-purity niobium. In 2024 the US Department of Defense funded a plant in Boyertown, Pennsylvania, to make high-purity niobium oxide. Molybdenum, tantalum, titanium or vanadium can replace niobium in steels, the survey adds, at some cost in performance or money.

Cooled below 9.25 kelvin, about −264 °C, pure niobium becomes a superconductor, Jefferson Lab reports. The laboratory’s electron accelerator puts the metal to work. Its 338 niobium cavities sit in liquid helium and push electrons to nearly the speed of light. Physicists use the beam to probe the quark structure of matter.

Properties

Properties of niobium 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	41
Standard atomic weight	92.906(1) Da	Da	IUPAC/CIAAW 2024
Melting point	2477 °C	°C	Los Alamos: 2477 °C
Boiling point	4744 °C	°C	Los Alamos: 4744 °C
Density	8.57 g/cm³	g/cm³
Electronegativity (Pauling)	1.6
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁴
Phase at 25 °C	solid

Safety

Niobium meets no hazard criterion under GHS, the UN’s Globally Harmonized System, in 307 of 529 company reports (58%). In 34% of reports it is classed as a flammable solid, with the signal word Danger. Haz-Map calls the element a severe skin irritant of low toxicity when swallowed. PubChem’s Laboratory Chemical Safety Summary for niobium sets out these classifications for workplaces that handle the metal.

Questions

Why is niobium also called columbium?

Charles Hatchett found the element in 1801 in columbite, a black mineral from America, and called it columbium. Heinrich Rose later gave it the name niobium, and the two names lived side by side: columbium in America, niobium in Europe. IUPAC settled on niobium in 1949 by CIAAW's date and in 1950 by Los Alamos's. Most metallurgists and all but one of the leading US commercial producers still call the metal columbium, Los Alamos says.

Which niobium alloys are superconductors?

Alloys of niobium with titanium, tin and aluminium are superconductors, and niobium-titanium wire is made into superconducting magnets, according to Jefferson Lab. Los Alamos describes magnets of niobium-zirconium wire that stay superconducting in strong magnetic fields. Tin-niobium wire magnets of just a few pounds, started with a small battery, give fields comparable to those of a 100 ton electromagnet, Los Alamos says.

Is niobium radioactive?

Natural niobium is a single stable isotope, niobium-93, which makes up all of the element by CIAAW's figures. Los Alamos puts the known isotopes at eighteen; the Atomic Mass Data Center (AMDC) lists 37, from niobium-79 to niobium-115. Niobium-95 has a half-life of 34.991 days in the AMDC list. IUPAC's periodic table notes its use in tumour research and imaging studies, with its isomer niobium-95m, an excited (metastable) state of the same nucleus, half-life 3.61 days in the AMDC list.

Does niobium tarnish in air?

Slowly. Los Alamos says the shiny white metal takes on a bluish cast after a long time in air at room temperature. From 200 °C it starts to oxidise, and niobium worked at even moderate temperatures has to be kept under a protective atmosphere. Los Alamos describes the oxide as mildly acidic.