Some elements exist in several different structural forms, called allotropes. Each allotrope has different physical properties.

For more information on the Visual Elements image see the Uses and properties section below.



A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.

Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f).

Atomic number
The number of protons in an atom.

Electron configuration
The arrangements of electrons above the last (closed shell) noble gas.

Melting point
The temperature at which the solid–liquid phase change occurs.

Boiling point
The temperature at which the liquid–gas phase change occurs.

The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.

Density (g cm−3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.

Relative atomic mass
The mass of an atom relative to that of carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists, the value given is the abundance weighted average.

Atoms of the same element with different numbers of neutrons.

CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.

Fact box

Group Melting point 2477°C, 4491°F, 2750 K 
Period Boiling point 4741°C, 8566°F, 5014 K 
Block Density (g cm−3) 8.57 
Atomic number 41  Relative atomic mass 92.906  
State at 20°C Solid  Key isotopes 93Nb 
Electron configuration [Kr] 4d45s1  CAS number 7440-03-1 
ChemSpider ID 22378 ChemSpider is a free chemical structure database


Image explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


The description of the element in its natural form.

Biological role

The role of the element in humans, animals and plants.

Natural abundance

Where the element is most commonly found in nature, and how it is sourced commercially.

Uses and properties

Image explanation
The propeller blades in the icon reflect the use of niobium and its alloys in the aviation industry.
A silvery metal that is very resistant to corrosion due to a layer of oxide on its surface.
Niobium is used in alloys including stainless steel. It improves the strength of the alloys, particularly at low temperatures. Alloys containing niobium are used in jet engines and rockets, beams and girders for buildings and oil rigs, and oil and gas pipelines.

This element also has superconducting properties. It is used in superconducting magnets for particle accelerators, MRI scanners and NMR equipment.

Niobium oxide compounds are added to glass to increase the refractive index, which allows corrective glasses to be made with thinner lenses.
Biological role
Niobium has no known biological role.
Natural abundance
The main source of this element is the mineral columbite. This mineral also contains tantalum and the two elements are mined together. Columbite is found in Canada, Brazil, Australia, Nigeria and elsewhere. Some niobium is also produced as a by-product of tin extraction.
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When examining minerals in the British Museum in 1801, Charles Hatchett was intrigued by a specimen labelled columbite. He suspected it contained a new metal, and he was right. He heated a sample with potassium carbonate, dissolved the product in water, added acid and got a precipitate. However, further treatment did not produce the element itself, although he named it columbium, and so it was known for many years.

Others doubted columbium, especially after the discovery of tantalum which happened the following year. These metals occur together in nature, and are difficult to separate. In 1844 the German chemist Heinrich Rose proved that columbite contained both elements and he renamed columbium niobium.

A sample of the pure metal was produced in 1864 by Christian Blomstrand who reduced niobium chloride by heating it with hydrogen gas.

Atomic radius, non-bonded
Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.

Covalent radius
Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination.

Electron affinity
The energy released when an electron is added to the neutral atom and a negative ion is formed.

Electronegativity (Pauling scale)
The tendency of an atom to attract electrons towards itself, expressed on a relative scale.

First ionisation energy
The minimum energy required to remove an electron from a neutral atom in its ground state.

Atomic data

Atomic radius, non-bonded (Å) 2.18 Covalent radius (Å) 1.56
Electron affinity (kJ mol−1) 88.381 Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)


Common oxidation states

The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.


Atoms of the same element with different numbers of neutrons.

Key for isotopes

Half life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Oxidation states and isotopes

Common oxidation states 5, 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  93Nb 92.906 100


Data for this section been provided by the British Geological Survey.

Relative supply risk

An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.

Crustal abundance (ppm)

The number of atoms of the element per 1 million atoms of the Earth’s crust.

Recycling rate

The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.


The availability of suitable substitutes for a given commodity.
High = substitution not possible or very difficult.
Medium = substitution is possible but there may be an economic and/or performance impact
Low = substitution is possible with little or no economic and/or performance impact

Production concentration

The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.

Reserve distribution

The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.

Political stability of top producer

A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.

Political stability of top reserve holder

A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.

Supply risk

Relative supply risk 7.6
Crustal abundance (ppm) 8
Recycling rate (%) >30
Substitutability Medium
Production concentration (%) 98
Reserve distribution (%) 97
Top 3 producers
  • 1) Brazil
  • 2) Canada
Top 3 reserve holders
  • 1) Brazil
  • 2) Canada
Political stability of top producer 48.1
Political stability of top reserve holder 48.1


Specific heat capacity (J kg−1 K−1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

Young's modulus

A measure of the stiffness of a substance. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.

Shear modulus

A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

Bulk modulus

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour pressure

A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

Specific heat capacity
(J kg−1 K−1)
265 Young's modulus (GPa) 104.9
Shear modulus (GPa) 37.5 Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - 2.32
x 10-11
x 10-9
x 10-6
x 10-5
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Listen to Niobium Podcast
Transcript :

Chemistry in its element: niobium


You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

(End promo)

Meera Senthilingam

This week, an element with some contradiction, as its namesake weeps, yet its chemistry is impassive. Here's Jon Steed:

Jon Steed

Niobium. What an evocative name! The element was christened after Niobe, the daughter of Tantalus in Greek mythology. Tantalus has an element named after him as well; tantalum which falls directly below niobium in the periodic table. Niobe had a fairly hard time of it. She was foolish enough to suggest that rather than worshipping invisible gods, it might be a nice idea to appreciate real people for a change. The Greek gods weren't very forgiving of this kind of hubris and as punishment killed all, or at least most, of her twelve children; the niobids. As a result Niobe fled to Mount Sipylus and was turned into stone. There is to this day a rock formation in the Aegean region of Turkey termed the 'weeping rock' that resembles a woman's face, purportedly Niobe's. Water seeps through the porous limestone of the weeping rock and is said to resemble Niobe's unceasing tears at the fate of the niobids. Niobe's apparent petrification and the subsequent seeping of mineral-laden water through the rock calls to mind the real chemical phenomenon of petrifying wells such as the one at Mother Shipton's Cave in Knaresborough in North Yorkshire. The evaporation of the salt-saturated water and subsequent mineral deposition means that these wells really can apparently turn common objects to stone.

Placing Niobe and her father Tantalus next to one another in the periodic table is no accident. Both niobium and tantalum are found together in the mineral columbite, a mixed oxide that also contains iron and manganese, and they have similar chemical and physical properties. In fact Niobium was originally named columbium after Columbia, because of its discovery in a mineral sent from America in 1801. The following half-century saw a great deal of confusion about exactly which possible new tantalum-like elements were present in these kinds of minerals and initially a number of Tantalus's children became immortalised as elements, with names such as pelopium, ilmenium and dianium. In the end only niobium survived. In the US niobium was called columbium, symbol Cb, all the way up until its official christening by the International Union of Pure and Applied Chemistry in 1950. The last paper published by the American Chemical Society that mentions columbium dates from 1953, with the rather unexciting title "Photometric Determination of Columbium, Tungsten, and Tantalum in Stainless Steels". This paper does hint at one of niobium's major uses though, as we will see. The 2010 Aldrich Catalogue of Fine Chemicals still has Columbium as an explanatory subheading for any confused Americans out there.

In fact, in contrast to the plucky Niobe, niobium is a pretty impassive element. It doesn't even react with the very oxidising acid aqua regia and, like tantalum, is inert to bodily fluids. This impassivity, coupled with its tendency to be coloured by anodisation means that it is sometimes used in jewellery and coinage. The anodising process results in a thin oxide layer that creates a range of permanent colours by diffraction of light. Since 2003, Austria has produced a series of silver-niobium euro coins with a niobium centre coloured blue, green, brown, purple, violet or yellow. Like the better known tungsten, niobium also forms a range of colourful oxide 'bronzes' ranging from deep blue to red depending on the degree of reduction.

Perhaps the most exciting modern day role of niobium, however, is in superconducting niobium-titanium alloy fibres. Niobium-titanium is a superconducting at temperatures below ten Kelvin and is used in a number of large superconducting magnets such as the Tevatron accelerator at Fermilab and most recently the Large Hadron Collider, where the niobium-containing magnets are cooled to 1.9 Kelvin and operate at magnetic fields of up to 8.3 Tesla. You can also find it in the superconducting magnets in hospital MRI scanners.

Niobium is a useful metal in a range of specialist alloys. In amounts as low as 0.1 per cent it has a significant strengthening effect on steel, making it suitable for use in gas pipelines for example. It is also involved in some highly temperature-stable superalloys used for engine parts in the aerospace industry.

Niobium very nearly became quite literally a household element because of its early role as the filament in incandescent light bulbs. Its impassivity and high melting point of 2468 centigrade lent themselves to this application but it was swiftly replaced by the even higher melting tungsten. Niobium is also a fairly dense element and it is this density that might account for its apparent rarity. Occurring at only twenty parts per million, it is 33rd in the hall of fame of most common elements in the Earth's crust. This surprisingly low value might arise from the 'missing' niobium sinking to the Earth's core during the planet's formation.

You don't tend to see a great many publications in the inorganic chemistry literature on niobium chemistry, although the metal is not particularly expensive so perhaps all that will change in this credit-crunched era. A classic paper is Dick Schrock's 1979 review of the chemistry of niobium and tantalum alkylidene complexes - compounds with a double bond between the metal and carbon. This paper contains a picture of one of my favourite organometallic compounds - actually a tantalum compound - in which the metal is sandwiched between two organic rings and bound to two delightfully simple carbon fragments; CH2 and CH3. This structure presages a wide range sandwich-type, metal based catalysts.

In terms of niobium molecular pin-ups, one of the most elegant is the very symmetrical cluster formed from an octahedron of six niobium ions and eighteen chlorides. An ion that highlight's niobium's tendency to form large, exotic multi-metallic clusters with halides and oxides.

When you look at the great sprawling mass of the periodic table, it's easy for your eye to get lost in the swathe of exotically and confusingly named transition metals somewhere around the dip in the middle. I hope that you will let the example of niobium remind you that there's nothing to weep about. The subtleties of these elements aren't too petrifying, and with a little creativity you may give birth to some chemistry that even the vengeful, ancient gods can be proud of.

Meera Senthilingham

Providing colour, superconducting abilities and molecular pin-ups - certainly something for the gods to be proud of. That was Durham University's Jon Steed with the tantalising chemistry of the element niobium.

Now next week, an element whose founder clearly didn't believe in risk assessments.

Lars Öhrström

Frequently after more spectacular chemistry demonstrations, the scientist on stage will warn the audience 'not to try this at home'. One person who certainly did not listen to such warnings was Swedish chemist Jöns Jacob Berzelius. Instead, he and his co-workers performed many groundbreaking experiments in the kitchen of his flat in the corner of Nybrogatan and Riddargatan in Stockholm. In 1815, for example, Berzelius isolated a new element from a mineral sent to him from the Swedish mining town of Falun and named it thorium after the Scandinavian god of thunder, Thor. Only to realise a few years later that he was wrong and what he though was a new element was in fact yttrium phosphate.

However, in 1828, by then long since world famous and credited with discovering three other elements, he received a strange mineral sample from the reverend Hans Esmark in Norway. In his new laboratory at the Swedish Royal Academy of Sciences, Berzelius isolated yet another element, this element is what we now call thorium.

Meera Senthilingham

And now you know its discovery, join Lars Öhrström from the Chalmers tekniska högskola in Sweden to find out the chemistry and applications of thorium in next week's Chemistry in its element. Until then, I'm Meera Senthilinghma and thankyou for listening.


Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by There's more information and other episodes of Chemistry in its element on our website at

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Visual Elements images and videos
© Murray Robertson 1998-2017.



W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.


Uses and properties

John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.


Supply risk data

Derived in part from material provided by the British Geological Survey © NERC.


History text

Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.



Produced by The Naked Scientists.


Periodic Table of Videos

Created by video journalist Brady Haran working with chemists at The University of Nottingham.