- Niobium (Nb) is a transition metal with atomic number 41, located in Group 5 of the periodic table between titanium and tantalum.
- It is a soft, ductile, lustrous, gray metal with excellent corrosion resistance and superconducting properties.
- Niobium has five valence electrons—two in the 5s subshell and three in the 4d subshell—and it most commonly exhibits the +5 oxidation state, though +3 and +4 states are also known. Its atomic structure consists of forty-one protons, typically fifty-two neutrons, and forty-one electrons arranged in five shells.
- Naturally occurring niobium consists almost entirely of one stable isotope, niobium-93 (⁹³Nb), though a number of short-lived radioactive isotopes exist.
- Niobium is relatively rare in the Earth’s crust, with an abundance of about 20 parts per million. It is not found in native metallic form, but occurs primarily in the minerals columbite ((Fe,Mn)(Nb,Ta)₂O₆) and pyrochlore ((Na,Ca)₂Nb₂O₆(OH,F)), the latter being the main commercial source. Significant deposits exist in Brazil (the largest producer), Canada, Australia, and parts of Africa. Extraction generally involves concentration of pyrochlore ore, conversion to niobium pentachloride (NbCl₅), and reduction with sodium or magnesium.
- Niobium was first discovered in 1801 by English chemist Charles Hatchett, who identified it in a mineral from Connecticut and named it columbium after the New World (Columbia). In 1844, German chemist Heinrich Rose re-examined the mineral and found it to be a distinct element closely related to tantalum, naming it niobium after Niobe, a figure from Greek mythology and the daughter of Tantalus. The name “niobium” was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1950, though “columbium” persisted in the United States for decades.
- Niobium has important uses in metallurgy, electronics, and superconductivity. It is a critical component of high-strength, low-alloy (HSLA) steels, where small amounts improve strength, toughness, and corrosion resistance, making them essential for pipelines, automotive components, and structural applications. Niobium is also used in nickel-based superalloys for jet engines, rocket components, and gas turbines due to its ability to maintain strength at high temperatures.
- One of niobium’s most notable properties is its ability to become superconducting at low temperatures (critical temperature ≈ 9.25 K). Niobium-titanium (NbTi) and niobium-tin (Nb₃Sn) alloys are the primary materials used for superconducting magnets in particle accelerators, MRI machines, and fusion research devices. Niobium oxide and niobium-doped materials are used in capacitors, optics, and electrochromic devices.
- Chemically, niobium is highly resistant to corrosion by acids and alkalis at room temperature due to its protective oxide layer, Nb₂O₅. It reacts at elevated temperatures with halogens, oxygen, nitrogen, and carbon to form a variety of stable compounds.
- Biologically, niobium has no known essential role in life and is generally considered to have low toxicity, though inhalation of dust should be avoided.
- From an environmental perspective, niobium mining and processing can lead to habitat disruption and waste generation, but the element itself is not a significant pollutant. Recycling from scrap metal is possible and helps reduce environmental impact.
