Chemical element · reference page

41Nb

Niobium

Niobium is element 41 (Nb), located in period 5, group 5 and the d block. At room temperature its reference phase is solid. Its electron configuration is [Kr] 4d4 5s1.

Atomic number41

Standard atomic weight92.90637(1)

Group5

Period5

Blockd

Electron configuration[Kr] 4d4 5s1

Electronic structure

What controls its chemistry

The d subshell participates in the chemistry of niobium. Transition metals can use electrons of similar energies in bonding, which is why variable oxidation states, coordination compounds and catalytic behaviour are common across the d block.

Its electron configuration, [Kr] 4d4 5s1, should be read together with the oxidation state of the compound: removing electrons changes which d orbitals are occupied and can alter colour, magnetism, bonding and reactivity.

Chemical forms

Compounds, ions and materials

For niobium, important chemical forms include metals and alloys, oxides, halides and coordination compounds. Variable oxidation states are common because s and d electrons have similar energies, and ligands around the metal ion can strongly alter colour, magnetism and reactivity.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 8.57 g/cm³. The melting point is 2 745 K (2 472 °C). The boiling point is 5 017 K (4 744 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where niobium is found and used

In practice, niobium is encountered in superconducting magnets, metallurgy, steel and jewellery.

In practice

Examples of real uses

Superconducting magnets

Niobium-based superconductors carry very large currents with negligible electrical resistance at cryogenic temperatures.

Metallurgy

Niobium is used in extraction, refining, alloying or heat-treatment processes that control the properties of metals.

Steel

Niobium changes the properties of steels or appears in steelmaking chemistry and alloy design.

Jewellery

Niobium is used for colour, corrosion resistance, rarity, polish or mechanical properties in jewellery alloys.

Periodic position

What its neighbours tell us

Niobium is in period 5 and group 5. In the neighbourhood shown here, it lies between zirconium and molybdenum in the same period; vanadium is above it and tantalum below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationtransition metal

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 12 · 1

Density8.57 g/cm³

Melting point2 745 K (2 472 °C)

Boiling point5 017 K (4 744 °C)

Pauling electronegativity1.6

First ionisation energy652.1 kJ/mol

Electron affinity88.52 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of niobium is associated with Charles Hatchett. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 92.90637(1). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Niobium has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with niobium depend on chemical form, dose and route of exposure. Pure niobium, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.