Niobium
[Kr] 4d⁴ 5s¹ · 2 · 8 · 18 · 12 · 1
A refractory metal with the highest superconducting transition temperature of any pure element, 9.25 K. Niobium alloys wind the magnets of every MRI scanner and of the Large Hadron Collider.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 41
- Atomic mass
- 92.906 а.е.м.
- Electron configuration
- [Kr] 4d⁴ 5s¹
- Electrons per shell
- 2 · 8 · 18 · 12 · 1
- Block
- d-block
- Group
- Vanadium group
- Period
- 5
- Electronegativity (Pauling)
- 1.6
- Electronegativity (Allen)
- 1.41
- Atomic radius
- 198 pm
- Covalent radius
- 164 pm
- Van der Waals radius
- 208 pm
- Ionisation energy 1
- 652.1 kJ/mol
- Ionisation energy 2
- 1 380 kJ/mol
- Ionisation energy 3
- 2 416 kJ/mol
- Ionisation energy 4
- 3 700 kJ/mol
- Ionisation energy 5
- 4 877 kJ/mol
- Electron affinity
- 86.1 kJ/mol
- Common oxidation states
- +5
- Oxidation states
- -3, -1, +1, +2, +3, +4, +5
Physical properties
- State at 25 °C
- solid
- Density
- 8.57 g/cm³
- Melting point
- 2 750 K · 2 476.9 °C
- Boiling point
- 5 017 K · 4 743.9 °C
- Speed of sound
- 3 480 m/s
Thermal properties
- Heat of fusion
- 30 kJ/mol
- Heat of vaporisation
- 689.9 kJ/mol
- Specific heat capacity
- 0.265 J/(g·K)
- Thermal conductivity
- 53.7 W/(m·K)
Mechanical properties
- Young's modulus
- 105 GPa
- Shear modulus
- 38 GPa
- Bulk modulus
- 170 GPa
- Poisson ratio
- 0.4
- Mohs hardness
- 6
- Brinell hardness
- 736 MPa
Electrical and magnetic properties
- Electrical resistivity
- 152 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- 9.25 K
Crystal structure
- Crystal structure
- body-centred cubic (bcc)
- Lattice constants
- a = 330.04 pm
Abundance
- In the crust
- 20 mg/kg
- In the ocean
- 1·10⁻⁶ mg/L
- In the universe
- 2 mg/kg
- In the human body
- 0 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 93Nb | 100 % | stable | — |
Niobium-93 is the only stable isotope. Niobium-94, half-life 20 000 years, forms in reactor structures and matters when decommissioning them.
Discovery
- Year of discovery
- 1801
- Discovered by
- Charles Hatchett
- Where
- England
- Origin of the name
- after Niobe, daughter of Tantalus: it always occurs with tantalum
History
Charles Hatchett found the element in 1801 in an ore sample sent to the British Museum from Connecticut. For half a century niobium was confused with tantalum, until Heinrich Rose separated them in 1846 and named it after Niobe, daughter of Tantalus.
Where it occurs
20 mg/kg of the crust. The main mineral is columbite-tantalite; over 90 % of world output comes from a single Brazilian deposit.
How it is produced
Aluminothermic reduction of pyrochlore concentrate gives ferroniobium for steel; the pure metal comes from vacuum reduction of the pentoxide.
Role in living things
No biological role. Niobium is biocompatible and non-allergenic, so it is used in piercings and implants.
Safety
The metal is harmless. Pentoxide dust irritates the airways.
Uses
- Microalloying steel: hundredths of a per cent sharply strengthen pipeline steels
- Superconducting magnets: Nb-Ti and Nb₃Sn in MRI and accelerators
- Superconducting cavities in linear accelerators
- Heat-resistant alloys for rocket nozzles
- Jewellery: anodised niobium takes durable colour without dye
Curiosities
- Every magnet in the Large Hadron Collider is wound with niobium–titanium wire.
- Niobium and tantalum are named for Niobe and her father Tantalus — the only such family pair in the table.
- In the United States niobium was officially columbium until the 1950s, and metallurgists still use that name in places.
- Anodising niobium produces the full colour spectrum by interference in the oxide film.