Periodic Table > Cerium
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses and properties facts below.

 

Fact box terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
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, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


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


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


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.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 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 (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact box

 
Group Lanthanides  Melting point 799 oC, 1470.2 oF, 1072.15 K 
Period Boiling point 3443 oC, 6229.4 oF, 3716.15 K 
Block Density (kg m-3) 6711 
Atomic number 58  Relative atomic mass 140.116  
State at room temperature Solid  Key isotopes 140Ce 
Electron configuration [Xe] 4f5d6s2  CAS number 7440-45-1 
ChemSpider ID 22411 ChemSpider is a free chemical structure database
 

Uses and properties terminology


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.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses and properties

 
Image explanation
The image is based on the asteroid Ceres, after which the element is named. The background is based on an early 17th-century astronomical map.
Appearance
Cerium is a grey metal. It is little used because it tarnishes easily, reacts with water and burns when heated.
Uses
Cerium is the major component of mischmetal alloy (just under 50%). The best-known use for this alloy is in ‘flints’ for cigarette lighters. This is because cerium will make sparks when struck. The only other element that does this is iron.

Cerium(Ill) oxide has uses as a catalyst. It is used in the inside walls of self-cleaning ovens to prevent the build-up of cooking residues. It is also used in catalytic converters. Cerium(III) oxide nanoparticles are being studied as an additive for diesel fuel to help it burn more completely and reduce exhaust emissions.

Cerium sulfide is a non-toxic compound that is a rich red colour. It is used as a pigment.

Cerium is also used in flat-screen TVs, low-energy light bulbs and floodlights.
Biological role
Cerium has no known biological role.
Natural abundance
Cerium is the most abundant of the lanthanides. It is more abundant than tin or lead and almost as abundant as zinc. It is found in a various minerals, the most common being bastnaesite and monazite.

Cerium oxide is produced by heating bastnaesite ore, and treating with hydrochloric acid. Metallic cerium can be obtained by heating cerium(III) fluoride with calcium, or by the electrolysis of molten cerium oxide.
 
Atomic data terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic data

 
Atomic radius, non-bonded (Å) 2.420 Covalent radius (Å) 1.84
Electron affinity (kJ mol-1) 62.715 Electronegativity
(Pauling scale)
1.120
Ionisation energies
(kJ mol-1)
 
1st
534.403
2nd
1046.865
3rd
1948.809
4th
3546.605
5th
6324.609
6th
7487.256
7th
-
8th
-
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Scarcity factor 8.0
Country with largest reserve base China
Crustal abundance (ppm) 0.3
Leading producer China
Reserve base distribution (%) 59.30
Production concentration (%) 97.40
Total governance factor(production) 8
Top 3 countries (mined)
  • 1) China
  • 2) USA
  • 3) CIS
Top 3 countries (production)
  • 1) China
  • 2) Russia
  • 3) Brazil
 

Oxidation states and isotopes


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

Terminology


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. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

 
Common oxidation states 4, 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  136Ce 135.907 0.185 > 0.7 x 1014 EC EC 
        > 4.2 x 1015 β- β- 
  138Ce 137.906 0.251 >3.7 x 1014 EC EC 
  140Ce 139.905 88.45
  142Ce 141.909 11.114 > 1.6 x 1017 β-β- 
 

Pressure and temperature - advanced terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, 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 (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the 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

 
Molar heat capacity
(J mol-1 K-1)
26.94 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - 2.47
x 10-11
8.91
x 10-8
2.97
x 10-5
2.33
x 10-3
6.91
x 10-2
1.04 9.56 60.8
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History

Cerium was first identified by the Jöns Berzelius and Wilhelm Hisinger in the winter of 1803/4. Martin Klaproth independently discovered it around the same time.


Although cerium is one of the 14 lanthanoid (aka rare earth) elements it was discovered independently of them. There are some minerals that are almost exclusively cerium salts such as cerite, which is cerium silicate. A lump of this mineral had been found in 1751 by Axel Cronstedt at a mine in Vestmanland, Sweden. He sent some to Carl Scheele to analyse it but he failed to realise it was new element. In 1803, Berzelius and Hisinger examined it themselves and proved that it contained a new element.


It was not until 1875 that William Hillebrand and Thomas Norton obtained a pure specimen of cerium itself, by passing an electric current through the molten cerium chloride.

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Podcasts

Listen to Cerium Podcast
Transcript :

Chemistry in Its Element - Cerium


(Promo)

 

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, this week we're meeting the chemical that behaves badly and won't obey the rules when it comes to compounds involving oxygen and if that wasn't inflammatory enough, it is also the source of sparks that brings a lighter to life. But thankfully it's also got a softer side and that is a soothing remedy for burns, as Andrea Sella knows only too well.

 

Andrea Sella

A few weeks ago I had a stupid accident in the lab; I wont go into the details; I am not terribly proud about what happened. But the result is I suffered from some superficial burns on my face and neck. I was seen to by a specialist nurse who nodded at me and then handed me tub of ointment. 'Its flammacerium', she said, 'apply it twice a day'. 'Flama what', I replied, 'cerium', she said. I was delighted. 'Cerium, it can not be serious, it's my favorite element'. The nurse laughed. Fortunately she didn't ask me why, she would have never got me out of the clinic. But perhaps if she listened to this Podcast, she will find out.

 

Cerium is one of the first members of a series of about 14 elements with exotic and evocative names often referred to as the 'rare earths' or 'lanthanides'. The most striking thing about these elements is their remarkable chemical similarity. So much so for almost a hundred years, chemists almost went mad trying to separate them. William Crookes, the great Victorian inventor and spectroscopist wrote in 1887, 'these elements perplex us in our researches; they baffle us in our speculations and haunt us in our very dreams. They stretch like an unknown sea before us marking mystifying and murmuring strange revelations and possibilities'. Yet Cerium stands out from the crowd with its insoluble ceramic oxide, Ceria which has changed our world. But I'm, getting ahead of myself.

 

The discovery of Cerium was an accident. Around 1800, a young geologist Wilhelm Hisinger was rock hunting on his father's estate on the island of Västmanland, in Sweden, and found a new mineral that struck him as unusually dense. Hoping that it might be an ore of the recently discovered element Tungsten, Hisinger sent a sample to that element's discoverer Carl Wilhelm Scheele who took a look and said rather unhelpfully that there was no Tungsten in it. Undeterred Hisinger went to work with the great Swedish analytical chemist theorist Jöns Jakob Berzelius. In 1803, they isolated a new metallic element that they separated, thanks to the insolubility of its oxide. The named the element after the asteroid Ceres, itself named after the Roman goddess of agriculture. At about the same time, the German analyst Martin Klaproth isolated the same element from a different Scandinavian mineral. Both reports appeared in the same journal a few months apart causing something of an academic clash over exactly who got there first. The isolation of the metal however would have to wait another 70 years until the electrolysis of molten Cerium Chloride.

 

The metal itself is nothing special to look at; it's a standard silver grey color and it tarnishes slowly in air as an oxide layer builds up on the surface. But in powdered form it is much more exciting. It is highly reactive particularly when alloyed with iron; it forms a brittle material ferrous cerium which sparks spectacularly when struck and is the basis of the flints of cigarette lighters and those exciting fire steels for chefs.   Why does it burn so furiously? Well Cerium is fairly electro positive. So it will give up its outer electrons easily. And the oxide Ceria that I alluded to earlier is almost brick like in its stability. So it gives out huge amount of energies when it combusts. Ceria is also very hard which has made it a useful roche or polish for lens. If you happen to want to grind or polish your own telescope, then cerium dioxide is probably what you will use.   But what makes the oxide really interesting is it misbehaves. Although the formula may appear to be CeO2, one cerium 2 oxygens in reality the compound always has slightly less than 2 oxygens; the surface is peppered with defects, gaps where an oxygen atom should be and the degree of imperfection varies; it depends very much on how the oxide is prepared or treated. So one of the headline uses for this apparently flawed oxide is in the catalytic converters of cars and trucks. A honeycomb of cerium dioxide helps to combust un-burnt fuel coming down the exhaust pipe by releasing oxygen during the oxygen lean part of the engine's cycle while picking the oxygen back up in the rich stage. As a nanopowder, mixed in with diesel fuel, it can clean up the otherwise sooty fumes produced by trucks and buses. So Cerium is critical for reducing the impact of the internal combustion engines that power our vehicles.   But if you take an even closer look at Ceria it becomes more confusing. At first sight it looks like a no-brainer. Cerium looses 4 electrons handing them over to the surrounding oxygen leaving aside defects, this means it has a 4+ oxidation state. But on very close inspection with x-ray spectroscopy its clear that the Cerium hangs on to at least some of those four electrons and its true oxidation state is in a quantum mechanical limbo some where between 3 and 4. Indeed the great Japanese spectroscopist Akio Kotani once wrote that 'there is no genuine example of Cerium 4'. And as always there is mystery concealed just beneath the surface of even the most apparently simple looking chemistry. So why you might ask, is Cerium a burn cream; that too is a mystery. The most that the doctors can tell me is that it seems to work. Something to which I can great fully attest.

 

Chris Smith

That's UCL's Andrea Sella on Cerium the element that sparks up lighters, vanishes burns and also helps us to clean up our act when it comes to pollution. Now next week it's definitely a case of don't blink, or you might miss it.

 

Phillip Ball

The nuclear collisions used to make them created only about one atom per hour. Yet 7 fleeting atoms of Seaborgium to work with, the researches figured out that it's a metal comparable to molybdenum and   tungsten. In such virtuoso experiments we can see the periodic table continuing to exert its pattern even among the elements that nature never glimpsed. 

 

Chris Smith

And Phil Ball will be telling us the story of those 7 atoms of Seaborgium next time. I do hope you can join us. I'm Chris Smith, thanks for listening. 

 

(Promo)

 

Chemistry in its elementbrought to you by the Royal society of chemistry and produced by thenakedscientists dot com. There's more information and other episodes of chemistry in its element on our website at chemistryworld dot org forward slash elements. 

 

(End promo)

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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.