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 1313°C, 2395°F, 1586 K 
Period Boiling point 3273°C, 5923°F, 3546 K 
Block Density (g cm−3) 7.90 
Atomic number 64  Relative atomic mass 157.25  
State at 20°C Solid  Key isotopes 158Gd 
Electron configuration [Xe] 4f75d16s2  CAS number 7440-54-2 
ChemSpider ID 22418 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 image reflects the past use of the element in television screens.
A soft, silvery metal that reacts with oxygen and water.
Gadolinium has useful properties in alloys. As little as 1% gadolinium can improve the workability of iron and chromium alloys, and their resistance to high temperatures and oxidation. It is also used in alloys for making magnets, electronic components and data storage disks.

Its compounds are useful in magnetic resonance imaging (MRI), particularly in diagnosing cancerous tumours.

Gadolinium is excellent at absorbing neutrons, and so is used in the core of nuclear reactors.
Biological role
Gadolinium has no known biological role, and has low toxicity.
Natural abundance
In common with other lanthanides, gadolinium is mainly found in the minerals monazite and bastnaesite. It can be commercially prepared from these minerals by ion exchange and solvent extraction. It is also prepared by reducing anhydrous gadolinium fluoride with calcium metal.
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Gadolinium was discovered in 1880 by Charles Galissard de Marignac at Geneva. He had long suspected that the didymium reported by Carl Mosander was not a new element but a mixture. His suspicions were confirmed when Marc Delafontaine and Paul-Emile Lecoq de Boisbaudran at Paris reported that its spectral lines varied according to the source from which it came. Indeed, in 1879 they had already separated samarium from some didymium which had been extracted from the mineral samarskite, found in the Urals. In 1880, Marignac extracted yet another new rare earth from didymium, as did Paul-Émile Lecoq de Boisbaudran in 1886, and it was the latter who called it gadolinium.

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) 2.34 Covalent radius (Å) 1.82
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
  152Gd 151.920 0.2
  154Gd 153.921 2.18
  155Gd 154.923 14.8
  156Gd 155.922 20.47
  157Gd 156.924 15.65
  158Gd 157.924 24.84
  160Gd 159.927 21.86 > 1.9 x 1019 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)
235 Young's modulus (GPa) 54.8
Shear modulus (GPa) 21.8 Bulk modulus (GPa) 37.9
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - 5.70
x 10-10
x 10-6
0.000429 0.0279 0.618 7.39 56.2 -
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Listen to Gadolinium Podcast
Transcript :

Chemistry in its element: gadolinium


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 Senthilingham

This week: the art of naming an element. Here's Simon Cotton:

Simon Cotton

It's always interesting to know where an element takes its name. The family of elements that we call the lanthanides, or lanthanoids, have a somewhat random selection of names. That's because identifying the 15 lanthanide elements took over one hundred and fifty years, from the isolation of the first compounds to the synthesis of the last lanthanide, radioactive promethium, in 1947.

Some are named after gods, such as cerium; some like europium are named after places; and others including gadolinium, the star of this podcast, derive their names from scientists.

Gadolinium is named after Johan Gadolin, a Finnish scientist who was both a chemist and geologist. In 1792 he isolated the first rare earth compound, what we now know as yttrium oxide, from a black mineral that had been discovered at Ytterby in Sweden. A few years later this ore, which contained a number of lanthanides, was named gadolinite. Because of the difficulty in separating the very similar lanthanides, it was not until 1880 that a Swiss chemist named de Marignac identified spectroscopic lines due to the element we now know as gadolinium. Six years later, in 1886, the French chemist de Boisbaudran isolated the pure oxide, and called the element gadolinium, as it was obtained from gadolinite. Metallic gadolinium was not isolated until 1935, and like all the other lanthanides, it is a reactive metal.

Nearly all the known chemistry of gadolinium is that of the gadolinium three plus (3+) ion. This ion is colourless and does not at first glance seem very interesting. But like most other lanthanides and indeed transition metals, it has several unpaired electrons, giving it interesting magnetic properties. In fact this ion has 7 unpaired electrons in its 4f orbitals giving it a very large magnetic moment, and scientists are currently interested in making use of this.

As everyone knows, chlorofluorocarbons, CFCs for short, have been widely used in the past in fridges and freezers as the refrigerant gas. CFCs contribute to both depleting the Ozone layer and they are also Greenhouse gases, and due to this their use in the developed world has largely ceased. Meaning a good, more environmentally friendly, replacement is needed. Gadolinium may prove useful the fridges of the future due to a process known as magnetic refrigeration or adiabatic demagnetisation.

It works like this: -

When a substance containing unpaired electrons is put into a magnetic field, the magnetic dipoles tend to align with the field, in the lowest energy state; this process releases heat, which can be taken away using an external cooling liquid. Now if you remove the coolant from the magnetic material, and switch off the magnetic field. The magnetic dipoles in the material randomises, and it cools down.

A magnetic fridge has actually been constructed making use of gadolinium's ability to do this. The fridge contains a wheel with segments of powdered gadolinium, and as the wheel turns it passes through a gap between the poles of a very powerful magnet. When gadolinium is in the magnetic field it heats up, so it has to be cooled down by passing water through it.

Then as the wheel turns and the gadolinium leaves the magnetic field, the gadolinium starts to cools even more. A second lot of water is then flowed over the metal, which in turn is cooled down. This cool water is then circulated through the cooling coils of the fridge.

It's makers based at Iowa State University, say that this 'magnetic' refrigeration is 20 to 30 percent more energy efficient than conventional refrigeration - adding to its 'green' credentials.

That use may lie in the future, but the use of gadolinium in Magnetic Resonance Imaging is very much in the present.

MRI is a routine non-invasive clinical method used to produce two-dimensional images of our tissues or organs for diagnostic purposes. When searching for blood vessels or tumours, contrast agents are injected intravenously to improve the image quality of the MRI signal, and these are normally aqueous solutions of gadolinium complexes.

The free Gd3+ ion has a similar ionic radius to Ca2+ but a greater charge, so gadolinium itself can not be used as it might interfere with various calcium roles in signalling within the body and therefore be toxic. So the gadolinium ions are turned into stable complexes before being used, by reacting them with ligands like diethylenetriamine pentacetic acid, known as DPTA. This ligand has 8 atoms to attach to gadolinium, meaning it is bound very tightly indeed, ensuring free, toxic, gadolinium is not released. Once injected the compound circulates though the vascular system and then is filtered out through the kidneys and excreted unchanged. All the evidence suggests that it is quite safe, but at present its use in pregnant women is discouraged, largely because its safety for the foetus has not been proved.

So Gadolinium - colourless and initially may not sound very interesting, but may hold the key to keeping your milk or butter cool without damaging our environment and may even help save your life.

Meera Senthilingham

So offering the potential to save our lives and the environment - quite an element. That was Uppingham School's Simon Cotton with the heroic chemistry of gadolinium. Now, next week, we go back to the importance of naming an element, but also its pronunciation.

Brian Clegg

You'd think it is pretty strightforward to decide what an element is called, but element 102 has had more than its fair share of misunderstandings and arguments. To begin with, there's the matter of how to pronounce its current name: no-bell-ium, as it comes from the same root as the Nobel prize; or no-beel-ium, modelled on the way we say 'helium'. Even the Royal Society of Chemistry's representatives had a raging discussion on this when I asked them, before plumping for no-beel-ium. And that's just the pronunciation, the name itself took a fair amount of sorting out.

Meera Senthilingham

And join Brian Clegg to find out how element 102 received its name, as well as the wonders of its chemistry, in next week's Chemistry in its element. Until then, thank you for listening, I'm Meera Senthilingham.


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.