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 Lanthanides  Melting point 1016°C, 1861°F, 1289 K 
Period Boiling point 3074°C, 5565°F, 3347 K 
Block Density (g cm−3) 7.01 
Atomic number 60  Relative atomic mass 144.242  
State at 20°C Solid  Key isotopes 142Nd 
Electron configuration [Xe] 4f46s2  CAS number 7440-00-8 
ChemSpider ID 22376 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 imagery and symbols used here reflect the use of neodymium in the manufacture of purple glass.
A silvery-white metal. It rapidly tarnishes in air.
The most important use for neodymium is in an alloy with iron and boron to make very strong permanent magnets. This discovery, in 1983, made it possible to miniaturise many electronic devices, including mobile phones, microphones, loudspeakers and electronic musical instruments. These magnets are also used in car windscreen wipers and wind turbines.

Neodymium is a component, along with praseodymium, of didymium glass. This is a special glass for goggles used during glass blowing and welding. The element colours glass delicate shades of violet, wine-red and grey. Neodymium is also used in the glass for tanning booths, since it transmits the tanning UV rays but not the heating infrared rays.

Neodymium glass is used to make lasers. These are used as laser pointers, as well as in eye surgery, cosmetic surgery and for the treatment of skin cancers.

Neodymium oxide and nitrate are used as catalysts in polymerisation reactions.
Biological role
Neodymium has no known biological role. It is moderately toxic and irritating to eyes.
Natural abundance
The main sources of most lanthanide elements are the minerals monazite and bastnaesite. Neodymium can be extracted from these minerals by ion exchange and solvent extraction. The element can also be obtained by reducing anhydrous neodymium chloride or fluoride with calcium.
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Neodymium was discovered in Vienna in 1885 by Karl Auer. Its story began with the discovery of cerium, from which Carl Gustav Mosander extracted didymium in 1839. This turned out to be a mixture of lanthanoid elements, and in 1879, samarium was extracted from didymium, followed a year later by gadolinium. In 1885, Auer obtained neodymium and praseodymium from didymium, their existence revealed by atomic spectroscopy. Didymium had been studied by Bohuslav Brauner at Prague in 1882 and was shown to vary according to the mineral from which it came. At the time he made his discovery, Auer was a research student of the great German chemist, Robert Bunsen who was the world expert on didymium, but he accepted Auer's discovery immediately, whereas other chemists were to remain sceptical for several years.

A sample of the pure metal was first produced in 1925.

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) 2.39 Covalent radius (Å) 1.88
Electron affinity (kJ mol−1) Unknown 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 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  142Nd 141.908 27.2
  143Nd 142.910 12.2
  144Nd 143.910 23.8 2.1 x 1015
  145Nd 144.913 8.3
  146Nd 145.913 17.2
  148Nd 147.917 5.8
  150Nd 149.921 5.6 1.33 x 1020 β-β- 


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 9.5
Crustal abundance (ppm) 0.3
Recycling rate (%) <10
Substitutability High
Production concentration (%) 97
Reserve distribution (%) 50
Top 3 producers
  • 1) China
  • 2) Russia
  • 3) Malaysia
Top 3 reserve holders
  • 1) China
  • 2) CIS Countries (inc. Russia)
  • 3) USA
Political stability of top producer 24.1
Political stability of top reserve holder 24.1


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)
190 Young's modulus (GPa) 41.4
Shear modulus (GPa) 16.3 Bulk modulus (GPa) 31.8
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - 4.55
x 10-11
x 10-7
0.000483 0.0412 1.07 13.4 101 - -
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Listen to Neodymium Podcast
Transcript :

Chemistry in its element: neodymium


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

(End promo)

Chris Smith

Hello, two for the price of one this week. Here's Andrea Sella.

Andrea Sella

As a graduate student I used to seal off NMR samples under vacuum. As the glass was heated by the torch, the flame would blaze with the fierce orange glow of the sodium lurking in the pyrex. It was all the glassblowing I could do. Anything more serious required a trip down to the ground floor to see our wizard glassblower, Geoffrey Wilkinson, a lovable rogue from the Black Country with an infectious laugh, and wit was as sharp as a razor.

One day, as he stood at his lathe with an orange inferno raging before him I asked him about the glasses he was wearing. "Didymium" he answered cryptically, and then noticing my blank look, he added "Cuts out the light. Try them." He passed me his specs, the lenses of a curious greeny-grey colour. I slipped them on and suddenly the flame was gone. All I could see was a red-hot piece of spinning glass unobscured by the glare. I gawped in wonder until Geoff pulled the specs off my face saying "Give 'em back ya fool" and went back to his work.

Didymium is not a name you will often find in textbooks these days. It is the name of a pair of elements which lie next to each other in the lanthanide or rare earth series - what used to be the Wild West of the periodic table. The fourteen elements that constitute the series are remarkable for their similarity. Nowhere else does one find a group of elements that so resemble each other in their chemical properties. Hence these elements proved incredibly difficult to separate from each other and purify. And to make matters worse, unlike other metals, the colours of rare earth metal compounds were pale changed little from one compound to the next, making it even harder to work out whether your material was pure. Amongst the many claims for the discovery of new elements was a report in 1839 by the Swedish chemist Carl Gustav Mosander of a supposed element he called "Didymium" - after the Greek word for twin.

The invention of spectroscopy by Gustov Kirchoff and Robert Bunsen (yup, he of the Bunsen burner) now came into its own. It was soon realized that the spectre of the rare earths were very characteristic, with sharp gas-phase-like lines both in the solid and solution. At last there was a means of establishing purity.

Bunsen, who, by the 1870s, was the world's leading authority on the spectroscopy of the rare earths set this element as a problem for one of his students Carl Auer, who began to carry out the hundreds of fractional crystallizations necessary to get it pure. By 1885 it was clear that Auer had not one but two elements on his hands - a bluish lilac one he called "Neodymium", the new twin - and a green one he named "Praseodymium" - the green twin, each with their own spectra which summed together were the same as those of Mosander's material. Bunsen was delighted and immediately gave his approval to his student's work.

But it would not be until the 1940s before fast and effective methods for the separation of the lanthanides would be developed. Rather than the series of excruciatingly tedious crystallizations, the American chemists led by Frank Spedding described ion exchange methods and then within a few years solvent extraction became prevalent and produced kilogram quantities of these elements. Suddenly, commercial applications became a real prospect.

Because the ions themselves have unpaired electrons, their magnetic properties have proved fascinating to scientists and lucrative to entrepreneurs. An alloy of neodymium, iron and boron discovered in the 1980s is ferromagnetic, yielding permanent magnets over 1000 times stronger than anything ever seen before. Neodymium ion borade magnets have not only found their way into almost billions of electric motors and electronic devices around the world but also into wonderful toys for children.

On the other hand, the sharp spectral lines that so fascinated Bunsen and generations of spectroscopists since, imply very precise electronic states. Embedding neodymium into synthetic gemstones such as garnet resulted in the Neodymium:YAG laser, the workhorse of industrial laser cutting tools with its brilliant infrared lines. Your personalised iPod was probably engraved with a YAG. Coupled with a frequency doubling crystal a YAG gives us the bright green laser pointer than some lecturers like to show off with.

But some lateral thinking in the 1940s by chemists at Corning Glassworks in the US gave the invention that changed glassblowing forever. Someone spotted that both praseodymium and neodymium had absorption lines corresponding almost exactly with that annoyingly brilliant orange sodium line. Corning began producing "Didymium glass" which acts as an optical notch filter to cut out the glare and effect remains as astonishing to me today as it was the first time I saw it. When, a few years ago, one of our glassblowers here at UCL retired, he phoned me up on his last day. "I have something for you," he said mysteriously. I went down to the basement and shook his hand to wish him well. And then, to my delight, he handed me his specs. "Didymium," he said, "You'll need these."

Chris Smith

Andrea Sella with the story of didymium, two elements rolled into one. And Andrea is back next week with a taste of a metal that melts in your mouth and possibly also in your hands.

Andrea Sella

But I'm sure you really want to know is, if this really is the M & M element, what does it taste like? I knew you would ask. So I had a quick lick a couple of days back and the answer is it doesn't actually taste of very much to be honest. There's a faintly astringent and metallic taste which lingers on your tongue for few hours. And when it is molten, sorry I'll leave that experiment for someone more intrepid than I.

Chris Smith

And you can catch the story of gallium, which is what he was eating, with Andrea Sella on next week's Chemistry in its element, that's of course assuming that his element eating antics haven't poisoned him in the meantime. I'm Chris Smith, thank you for listening and goodbye.


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.