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 1663°C, 3025°F, 1936 K 
Period Boiling point 3402°C, 6156°F, 3675 K 
Block Density (g cm−3) 9.84 
Atomic number 71  Relative atomic mass 174.967  
State at 20°C Solid  Key isotopes 175Lu 
Electron configuration [Xe] 4f145d16s2  CAS number 7439-94-3 
ChemSpider ID 22371 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 is based on the civic coat of arms for the city of Paris (Latin name ‘Lutetia’), which gives the element its name.
A silvery-white, hard, dense metal.
Lutetium is little used outside research. One of its few commercial uses is as a catalyst for cracking hydrocarbons in oil refineries.
Biological role
Lutetium has no known biological role. It has low toxicity.
Natural abundance
In common with many other lanthanides, the main source of lutetium is the mineral monazite. It is extracted, with difficulty, by reducing the anhydrous fluoride with calcium metal.
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The honour of discovering lutetium went to Georges Urbain at the Sorbonne in Paris, because he was the first to report it. The story began with the discovery of yttrium in 1794 from which several other elements – the rare earths (aka lanthanoids) – were to be separated, starting with erbium in 1843 and ending with lutetium in 1907.

Other chemists, namely Karl Auer in Germany and Charles James in the USA, were about to make the same discovery. Indeed James, who was at the University of New Hampshire, was ahead of Urbain and had extracted quite a lot of the new metal, but he delayed publishing his research. A sample of pure lutetium metal itself was not made until 1953.

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) 2.24 Covalent radius (Å) 1.74
Electron affinity (kJ mol−1) 32.81 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
  175Lu 174.941 97.40
  176Lu 175.943 2.60 3.73 x 1010 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)
154 Young's modulus (GPa) 68.6
Shear modulus (GPa) 27.2 Bulk modulus (GPa) 47.6
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - 3.28
x 10-11
x 10-7
x 10-5
0.00628 0.211 3.18 26.7 -
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Listen to Lutetium Podcast
Transcript :

Chemistry in its element: lutetium


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: an element that was worth the wait. Here's Simon Cotton:

Simon Cotton

All chemists have their favourite elements, often for some personal reasons. In my case, that would be iron, as I spent three years of a PhD working on iron compounds. But it could also be cobalt, because cobalt is used to make the blue colour in many of my favourite stained glass windows in churches and cathedrals. Or it could be the last of the lanthanides - lutetium.

After completing my PhD, I carried out postdoctoral research trying to make new organometallic compounds of the metallic elements with electrons in their 4f subshells, known as the lanthanides. Until then, all the structures of these compounds that had been isolated contained organic rings bound side-on, or as organometallic chemists say, polyhapto-.

This research was, well, challenging. The compounds did not just catch fire in air, sometimes they caught fire in the inert atmospheres of glove boxes. It took me two years but eventually I managed to make compounds of lutetium, and also ytterbium. My colleague, Alan Welch, did an X-ray diffraction study using crystals of the lutetium compound, and found that the rings were bound in a way that had not been seen in lanthanides before, end-on or monohapto-.

This discovery was particularly pleasing because it was also the first four coordinate compound of any lanthanide. Mind you, what put it into perspective was that on the other side of the bench from me, an extremely talented and productive Indian chemist named Joginder Singh Ghotra made the first three coordinate compounds for yttrium and all the 14 stable lanthanides, not just lutetium.

So I've got good memories of lutetium, but what does lutetium matter to other chemists?

All the lanthanides took a long while to be discovered. Partly because neighbouring lanthanides tend to be very, very similar chemically, making them hard to separate. Another problem was that no one knew how many there were meant to be, as there were no theories of electronic structure or atomic number at the time.

Lutetium was actually the last lanthanide to be isolated in 1907; and was simultaneously discovered by three chemists working in different parts of the world.

They were the Austrian Carl Auer von Welsbach, the American Charles James, and Georges Urbain from France. Urbain was first to successfully separate lutetium from its neighbour, ytterbium, so he was given the privilege of naming the element. And being a good Frenchman, he selected the Latin name for Paris, lutetia.

So why was lutetium the last lanthanide to be discovered? Two reasons. As the atomic number of an element increases, its abundance decreases. Secondly elements with even atomic numbers, like ytterbium, are more abundant than elements with odd atomic numbers, such as lutetium. This is summarised in what is called the Oddo-Harkins rule, which sounds like something out of a Tolkien novel.

Additionally because lutetium has a filled 4f (NB, Simon Cotton says 4d here) subshell, it is spectroscopically rather transparent and it does not form coloured compounds, and so it is quite easy to overlook.

There is more than a hundred times more cerium, the most abundant lanthanide, in the earth than there is lutetium, the least abundant. This makes lutetium and its compounds rather expensive. Having said that, it is more abundant in the earth than elements like silver or gold, or the platinum metals.

Lutetium is the last of its family and the smallest. In size it is much nearer to yttrium and scandium, so some versions of the Periodic Table have lutetium directly under Sc and Y, preceded by the lanthanides from lanthanum to ytterbium.

The pure element is a silvery metal, and is similar to calcium and magnesium in its reactivity.

Lutetium and its compounds have found some applications, the most important of these is the use of the oxide in making catalysts for cracking hydrocarbons in the petrochemical industry. But there are other more specialist uses, such as using the radioactive Lutetium-177 isotope in cancer therapy. Lutetium ions were also used to dope gadolinium gallium garnet to make magnetic bubble computer memory that was eventually replaced by modern-day hard drives.

Lutetium triflate has also been found to be a very effective recyclable catalyst for organic synthesis in aqueous systems - it avoids the use of organic solvents, giving it green credentials - but because of its cost, it will never be as popular as the triflates of some other lanthanides.

It's fair to say that lutetium is still an element looking for its niche in the world, but I predict that more specialist uses will be forthcoming as the twenty-first century unfolds.

Meera Senthilingham

So keep your eyes peeled for lutetium popping up in medicine and our industries in the future. That was Simon Cotton with the long-awatied chemistry of the lanthanide lutetium. Now, next week, we're making new elements.

Andrea Sella

This is not work for the lone experimenter working in a shed somewhere. These are experiments of extraordinary subtlety and complexity. And the problem is not just making the new element but also figuring out what you've got at the end. The problem is that you only make a few atoms at a time and these products tend to be spectacularly unstable so you sometimes have only a few milliseconds in which to work out what you've got. It's complex. It's expensive. And very very clever. And each new atom really is a whole new chemical world to explore. Can it be any wonder that it attracts fortune seekers?

Meera Senthilingham

And join University College London's Andrea Sella to find out how elements 116 and 118 were discovered, as well as which fortune seekers found them, in next week's Chemistry in its element. Until then, I'm Meera Senthilingham and thank you 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

(End promo)
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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.