WebElements

Periodic Table

niobium

Atomic number: 41
Atomic weight: 92.90638
Symbol: Nb
Group number: 5
Electronic configuration: [Kr].4d4.5s1

Description

The name niobium was adopted by IUPAC in 1950, but a few commercial producers still refer to it as Columbium.

Niobium is a shiny, white, soft, and ductile metal, and takes on a bluish cast when exposed to air at room temperatures for a long time. The metal starts to oxidise in air at elevated temperatures, and when processed at even moderate temperatures must be placed in a protective atmosphere.

General information

Discoveror: Charles Hatchett
Date discovered: 1801
Discovered at: England
Meaning of name: From the Greek word "Niobe" meaning "daughter of Tantalus" (tantalum is closely related to niobium in the periodic table)

Physical data

Standard state: solid at 298 K
Colour: grey metallic
Density of solid at ambient temperature/kg m-3: 8570
Molar volume/cm3: 10.83

Radii /pm

Atomic: 198
Covalent (single bond):
Pauling radius for the ion [Nb]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius181.9no data78.9no data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 1.6
Allred Rochow: 1.23

Crystal Structure

structure: bcc (body-centred cubic)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

ball-and-stick.gif

Temperatures (/K)

melting point: 2750
boiling point: 5017

Enthalpies /kJ mol-1

fusion: 26.9
vaporization: 690

single bond enthalpies:
Nb-F Nb-Cl Nb-Br Nb-I Nb-Nb
no data no data no data no data 511

Ionization enthalpies /kJ mol-1

Number Enthalpy
1st664
2nd1382
3rd2416
4th3695
5th4877
6th9900
7th12100

Isotopes

This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
93Nb92.9063772 (27)100

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Nb.html