Niobium
Atomic Data
| Atomic Number | 41 |
| Symbol | Nb |
| Atomic Weight | 92.906 u |
| Density (STP) | 8.57 g/cm³ |
| Melting Point | 2476.85 °C (2750 K) |
| Boiling Point | 4743.85 °C (5017 K) |
| Electronegativity | 1.6 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d4 5s1 |
| Oxidation States | +3, +5 |
| Phase at STP | Solid |
| Category | Transition Metal |
| Period / Group | 5 / 5 |
| CAS Number | 7440-03-1 |
Electron Configuration
[Kr] 4d4 5s1
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 4 | 40 |
| O | 5 | 5s | 1 | 41 |
| Total | 41 | 41 | ||
Isotopes of Niobium
Niobium is monoisotopic: ⁹³Nb is its only naturally occurring stable isotope, accounting for 100% of all natural Niobium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Niobium-93 | ⁹³Nb | 41 | 52 | 100 | Stable |
Abundance & Occurrence
Niobium is present in Earth's crust at approximately 20 ppm by mass and at approximately 2 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Dust inhalation: Niobium metal dust is a respiratory irritant; as with other refractory metals, grinding and machining generate fine particles that should not be inhaled: use dust-rated respiratory protection.
- Niobium pentoxide dust: Nb2O5 dust is an irritant to eyes and airways; limited data suggests low acute toxicity, but chronic high-level inhalation should be avoided.
- Fire hazard: fine powder: Finely divided niobium powder can be combustible; handle powder under inert gas or with appropriate Class D fire-suppression materials.
- General precautions: Niobium is considered to have low systemic toxicity; standard metal handling practices (gloves, eye protection, ventilation) are appropriate for most laboratory uses.
Niobium in the Real World
Real-World Uses
- High-strength steels: Niobium microalloying (0.03–0.1%) refines grain size and increases yield strength in HSLA steels used in oil and gas pipelines, automotive body panels, bridges, and structural beams without requiring heat treatment.
- Superconducting magnets: Niobium-titanium (NbTi) and niobium-tin (Nb₃Sn) alloys become superconducting below 10 K and carry enormous currents without resistance, forming the magnets in MRI machines, particle accelerators (LHC), and proposed fusion reactors.
- Superalloys for jet engines: Niobium additions to nickel-based superalloys (e.g. Inconel 718) stabilise the gamma-double-prime strengthening phase, enabling turbine discs and combustion liners to operate at higher temperatures.
- Niobium capacitors: Niobium oxide capacitors are a stable, lower-cost alternative to tantalum in mobile phones and consumer electronics where reliability and compact size are required.
- Optical glass: Niobium oxide is added to specialty optical glasses to increase refractive index, used in compact camera lenses, eyeglasses, and fibre-optic components.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is niobium used for?
Niobium's primary use: over 80% of world production: is in high-strength low-alloy (HSLA) steels used in oil and gas pipelines, automotive structural parts, and construction. Adding small amounts of niobium grain-refines steel, dramatically increasing strength and toughness. Niobium is also used in superconducting alloys (niobium-tin and niobium-titanium) for MRI magnets and particle accelerator magnets.
Is niobium a superconductor?
Elemental niobium is a superconductor below its critical temperature of 9.2 K (about -264 °C). This is the highest critical temperature among elemental metals. Its alloys, particularly niobium-titanium (NbTi) and niobium-tin (Nb3Sn), remain superconducting at higher magnetic fields and are the workhorse materials in superconducting magnets for MRI scanners and the Large Hadron Collider.
How was niobium discovered?
Niobium was first discovered in 1801 by British chemist Charles Hatchett in a mineral sent to the British Museum from Connecticut, which he named columbite. He called the new element columbium. However, the element was confused with tantalum for decades. In 1864, Christian Wilhelm Blomstrand definitively showed it was a distinct element. The name niobium, after Niobe the daughter of Tantalus, was officially adopted by IUPAC in 1949, though 'columbium' persisted in US industry for many years.
How does niobium strengthen steel?
Niobium strengthens steel through a mechanism called grain refinement and precipitation hardening. In molten steel, niobium forms niobium carbonitride precipitates that pin grain boundaries, preventing grains from growing large during hot rolling. Smaller grains mean more grain boundaries, which block dislocation movement and increase strength. This allows engineers to achieve high strength with much less steel, reducing weight in vehicles and infrastructure.