Niobium (Nb)

Almost every large-bore MRI magnet and every dipole in the Large Hadron Collider is wound with niobium-titanium wire — it is the workhorse superconductor of the industrial world, and there is no cheap substitute. Around 90% of world supply comes from a single mine in Araxá, Brazil, one of the more extreme supply concentrations for any industrial metal. Niobium was named after Niobe, daughter of Tantalus, because it is chemically so like tantalum that the two were confused for forty years; American metallurgists called it columbium until 1949 and some still do.

Properties

Atomic number

41

Symbol

Nb

Standard atomic weight

92.906 u

Category

Transition metal

Group

5

Period

5

Block

d-block

Electron configuration

[Kr] 5s¹ 4d⁴

Electrons per shell

2, 8, 18, 12, 1

Melting point

2,750 K — 2476.8 °C — 4490.3 °F

Boiling point

5,017 K — 4743.9 °C — 8570.9 °F

Density

8.57 g/cm³

Electronegativity

1.6 (Pauling)

Oxidation states

+5, +3

Discovered

1801 by Charles Hatchett

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁴

Noble gas shorthand

[Kr] 5s¹ 4d⁴

Shells

K: 2 · L: 8 · M: 18 · N: 12 · O: 1

What it is used for

• Micro-alloying pipeline and structural steel, at a few hundred parts per million
• Niobium-titanium superconducting wire in MRI magnets and the LHC
• Superconducting radio-frequency cavities in particle accelerators
• Hypoallergenic jewellery and body piercings
• Jet engine and rocket nozzle superalloys

Anomalous electron configuration: [Kr] 5s¹ 4d⁴ rather than the predicted 5s² 4d³.

Neighbours in the table

Group 5

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Niobium sits in group 5 with vanadium, tantalum, dubnium.