# Cerium

**Cerium** (symbol Ce, atomic number 58) is a silvery, ductile and malleable metal of the lanthanide series, the most abundant of the rare earth elements in the [Earth's crust](https://www.edgepedia.org/earths-crust).<sup>[1](https://periodic-table.rsc.org/element/58/)</sup><sup> • </sup><sup>[2](https://www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information)</sup> It was identified in 1803, named after the asteroid Ceres, and its oxide, ceria (CeO₂), has become one of the most industrially important rare earth compounds, central to automotive exhaust catalysis, glass polishing, and lighter flints.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup><sup> • </sup><sup>[3](https://www.sciencedirect.com/science/article/pii/S0920586118306977)</sup>

| Key fact | Detail |
|---|---|
| Atomic number / mass | 58; relative atomic mass 140.116; electron configuration [Xe] 4f¹5d¹6s²; CAS number 7440-45-1<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> |
| Physical properties | Melting point 799 °C (1470 °F, 1072 K); boiling point 3443 °C; density 6.77 g/cm³; solid at 20 °C<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> |
| Discovery | Identified in the winter of 1803/4 by Jöns Berzelius and Wilhelm Hisinger in Sweden, and independently by Martin Klaproth in Germany; named after the asteroid Ceres<sup>[1](https://periodic-table.rsc.org/element/58/)</sup><sup> • </sup><sup>[4](https://acs.digitellinc.com/p/s/multiple-discoveries-of-cerium-667444)</sup> |
| Crustal abundance | 60 parts per million, the 25th most abundant of the 78 common elements in the Earth's crust and the most abundant rare earth element<sup>[2](https://www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information)</sup> |
| Stable isotopes | Four: ¹³⁶Ce (0.185%), ¹³⁸Ce (0.251%), ¹⁴⁰Ce (88.45%), and ¹⁴²Ce (11.114%)<sup>[5](https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ce)</sup> |
| Signature chemistry | Reversible Ce³⁺/Ce⁴⁺ redox couple, the basis of the oxygen storage capacity exploited in three-way automotive catalysts<sup>[3](https://www.sciencedirect.com/science/article/pii/S0920586118306977)</sup> |
| Best-known use | Mischmetal, just under 50% cerium, used for lighter flints; cerium sparks when struck, and the only other element that does this is iron<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> |

## Discovery and naming

The mineral that led to cerium was found decades before the element. In 1751 the Swedish mineralogist Axel Cronstedt found a dense new mineral at a mine in Vestmanland, Sweden, and sent a sample to Carl Scheele, who analyzed it but failed to realize it contained a new element. In 1803 Berzelius and Hisinger examined the mineral themselves and proved that it contained a new element; the mineral, cerite, is cerium silicate.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup>

The discovery was a shared one. Most lists credit the team of Wilhelm Hisinger and Jöns Jakob Berzelius in Sweden and, independently, Martin Heinrich Klaproth in Germany, both of whom published claims in 1803.<sup>[4](https://acs.digitellinc.com/p/s/multiple-discoveries-of-cerium-667444)</sup> According to the CIAAW account, Klaproth called the new earth "ochroeite" for its yellow color, while Berzelius and the mineralogist Wilhelm von Hisinger called it ceria.<sup>[6](https://www.ciaaw.org/cerium.htm)</sup> The name cerium derives from the planetoid Ceres, discovered by Giuseppe Piazzi in 1801 and named for the Roman goddess of agriculture and harvest.<sup>[6](https://www.ciaaw.org/cerium.htm)</sup>

Obtaining the metal itself took another seven decades. It was not until 1875 that William F. Hillebrand and Thomas H. Norton obtained a pure specimen by passing an electric current through molten cerium chloride.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup><sup> • </sup><sup>[6](https://www.ciaaw.org/cerium.htm)</sup>

## Physical and chemical character

Cerium is a gray metal that tarnishes easily in air as an oxide layer builds up, reacts with water, and burns when heated; it is little used in metallic form for these reasons.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> In powdered form it is far more reactive: finely divided cerium powder is pyrophoric, reacts vigorously with water or moist air generating flammable fumes, and is classified as a flammable solid for transport.<sup>[7](https://cameochemicals.noaa.gov/chemical/2844)</sup> Alloyed with iron it forms the brittle pyrophoric material used in lighter flints and fire steels, sparking spectacularly when struck.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup>

The element's defining chemical feature is the accessibility of two oxidation states, Ce³⁺ and Ce⁴⁺, in aqueous solution and in its oxides.<sup>[8](https://pubs.usgs.gov/fs/2002/fs087-02/index.html)</sup> Common oxidation states are 4 and 3.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> This pair underlies nearly all of cerium's technological value, because CeO₂ can reversibly release and take up oxygen:

\[ \mathrm{CeO_2} \rightleftharpoons \mathrm{CeO_{2-x}} + \tfrac{x}{2}\,\mathrm{O_2} \]

Notably, CeO₂ keeps its cubic fluorite crystal structure even after losing considerable lattice oxygen and forming many oxygen vacancies, and the reduced oxide is readily reoxidized.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0920586118306977)</sup>

## Isotopes

Natural cerium consists of four isotopes. ¹⁴⁰Ce dominates at 88.45% natural abundance, with ¹⁴²Ce at 11.114%, and trace ¹³⁶Ce (0.185%) and ¹³⁸Ce (0.251%).<sup>[5](https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ce)</sup> The standard atomic weight, 140.116(1), has held since the 1995 report of the IUPAC Commission on Isotopic Abundances and Atomic Weights, based on new isotope-abundance data.<sup>[6](https://www.ciaaw.org/cerium.htm)</sup> The rare isotopes ¹³⁸Ce and ¹⁴⁰Ce are decay products of the long-lived minor isotopes ¹³⁸La and ¹⁴⁴Nd respectively.<sup>[6](https://www.ciaaw.org/cerium.htm)</sup>

## Abundance and minerals

Cerium is the most abundant of the lanthanides, more abundant than tin or lead and almost as abundant as zinc.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> USGS places it at 60 parts per million in the crust, the 25th most abundant of the 78 common elements, at the top of a rare earth range that falls to about 0.5 ppm for thulium and lutetium.<sup>[2](https://www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information)</sup> Its distribution in soils closely tracks that of lanthanum and yttrium.<sup>[9](https://pubs.usgs.gov/sir/2017/5118/elements/Cerium/Ce_txt.html)</sup>

The principal economic sources of rare earths are the minerals bastnaesite, monazite, and loparite and the lateritic ion-adsorption clays.<sup>[2](https://www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information)</sup> Bastnaesite and monazite are the most common cerium minerals.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup> Cerium oxide is produced by heating bastnaesite ore and treating it with hydrochloric acid; metallic cerium is obtained by heating cerium(III) fluoride with calcium or by electrolysis of molten cerium oxide.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup>

## Ceria in catalysis

The major commercial application of CeO₂ is the treatment of emissions from internal combustion engines, where ceria-based materials have been used for about 35 years.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0920586118306977)</sup> In the three-way catalyst, a ceria-zirconia mixed oxide serves as the oxygen storage component: under oxygen-rich (lean) conditions it stores excess oxygen by oxidizing Ce³⁺ to Ce⁴⁺, and under rich conditions it releases oxygen, buffering the exhaust stoichiometry so the precious metal catalyst can convert carbon monoxide, hydrocarbons, and nitrogen oxides simultaneously.<sup>[10](https://www.nature.com/nature-index/topics/l4/ceria-zirconia-catalysts-for-automotive-emissions-control)</sup><sup> • </sup><sup>[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC11243869/)</sup> Cerium oxide was introduced into catalysis in 1976, initially not as a catalyst itself, and solid solutions of cerium and zirconium oxides replaced pure ceria in converters because of their higher oxygen storage capacity.<sup>[12](https://www.cambridge.org/core/journals/mrs-bulletin/article/abs/nanostructured-cerium-oxide-ecocatalysts/594109B60740890F69FE5642D0553563)</sup> Ceria also appears on the inside walls of self-cleaning ovens to prevent the buildup of cooking residues, and cerium(III) oxide nanoparticles have been studied as a diesel fuel additive to help fuel burn more completely.<sup>[1](https://periodic-table.rsc.org/element/58/)</sup>

Beyond vehicles, the Ce³⁺/Ce⁴⁺ redox couple supports applications in fuel cells, water-gas shift and reforming reactions, and the catalytic removal of air pollutants such as CO, NOₓ, volatile organic compounds, soot, and SOₓ.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0920586118306977)</sup><sup> • </sup><sup>[13](https://pubs.rsc.org/en/Content/ArticleLanding/2023/TA/D3TA03310D)</sup> In clean energy, cerium is used in nickel metal hydride batteries found in most hybrid and electric vehicles and in phosphor powders for fluorescent lamps; a 2011 US Department of Energy assessment judged cerium likely to be in surplus in both the short and medium terms because it is produced by all new rare earth mines.<sup>[14](https://www.energy.gov/documents/doecms2011finalfullpdf)</sup>

## Glass polishing

Cerium oxide polishes glass and silicon better than any other substance, and it works largely by chemical reaction rather than abrasion.<sup>[15](https://pubs.usgs.gov/of/2011/1189/of2011-1189.pptx.pdf)</sup> In the "chemical tooth" model, hydroxyl groups on the ceria surface form strong Ce–O–Si bonds with silanol groups on the glass surface; these bonds are much stronger than the Si–O–Si bonds of the glass, so material is removed as lumps of Ce–O–Si bonds by combined chemical reaction and mechanical abrasion.<sup>[16](https://doi.org/10.1557/s43578-020-00060-x)</sup> Surface Ce³⁺ sites, stabilized by oxygen vacancies, are responsible for the high reactivity with silica films, and current research aims to raise the surface Ce³⁺ concentration through doping or coating.<sup>[16](https://doi.org/10.1557/s43578-020-00060-x)</sup> The scale of the use is large: in 2008 the glass industry consumed 28,400 tonnes of rare earth oxides, of which cerium oxide accounted for 65 percent.<sup>[17](https://pubs.usgs.gov/sir/2011/5094/pdf/sir2011-5094.pdf)</sup>

## Cerium in ocean geochemistry

Cerium is the only rare earth element that commonly changes valence under Earth-surface conditions, and this gives it a distinctive role as a redox tracer. In oxygenated seawater, soluble Ce³⁺ is oxidized to insoluble Ce⁴⁺ and scavenged, depleting seawater in cerium relative to its lanthanide neighbors and producing the "cerium anomaly" recorded in marine sediments.<sup>[18](https://www.nature.com/articles/345421a0)</sup><sup> • </sup><sup>[19](https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.927826/full)</sup> A 1990 Nature study found that the negative Ce anomaly in seawater results from microbial oxidation followed by preferential scavenging of Ce(IV), with no abiotic oxidation detectable.<sup>[18](https://www.nature.com/articles/345421a0)</sup> Because the anomaly responds to oceanic oxygen levels, sedimentary cerium anomalies are used as a proxy for paleo-oceanic redox conditions.<sup>[19](https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.927826/full)</sup>

## Biology and safety

Cerium has no known biological role and is considered relatively nontoxic.<sup>[9](https://pubs.usgs.gov/sir/2017/5118/elements/Cerium/Ce_txt.html)</sup> The metal itself demands care: bulk cerium burns readily at high temperature and may be difficult to extinguish, and metallic fires must not be doused with water, which generates hydrogen gas; dry sand or class D extinguishers are the recommended agents.<sup>[7](https://cameochemicals.noaa.gov/chemical/2844)</sup>

## References

1. [Cerium, element information, properties and uses, Royal Society of Chemistry](https://periodic-table.rsc.org/element/58/)
2. [Rare Earths Statistics and Information, U.S. Geological Survey, National Minerals Information Center](https://www.usgs.gov/centers/national-minerals-information-center/rare-earths-statistics-and-information)
3. [A review on oxygen storage capacity of CeO2-based materials, Catalysis Today 327 (2019) 90-115](https://www.sciencedirect.com/science/article/pii/S0920586118306977)
4. [Multiple discoveries of cerium, American Chemical Society](https://acs.digitellinc.com/p/s/multiple-discoveries-of-cerium-667444)
5. [Atomic Weights and Isotopic Compositions for Cerium, NIST](https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ce)
6. [Atomic Weight of Cerium, Commission on Isotopic Abundances and Atomic Weights (CIAAW)](https://www.ciaaw.org/cerium.htm)
7. [CERIUM, SLABS, INGOTS OR RODS, CAMEO Chemicals, NOAA](https://cameochemicals.noaa.gov/chemical/2844)
8. [Rare Earth Elements: Critical Resources for High Technology, USGS Fact Sheet 087-02](https://pubs.usgs.gov/fs/2002/fs087-02/index.html)
9. [Cerium (Ce), USGS Scientific Investigations Report 2017-5118](https://pubs.usgs.gov/sir/2017/5118/elements/Cerium/Ce_txt.html)
10. [Ceria-Zirconia Catalysts for Automotive Emissions Control, Nature Index](https://www.nature.com/nature-index/topics/l4/ceria-zirconia-catalysts-for-automotive-emissions-control)
11. [Microwave-Based State Diagnosis of Three-Way Catalysts, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11243869/)
12. [Nanostructured Cerium Oxide Ecocatalysts, MRS Bulletin](https://www.cambridge.org/core/journals/mrs-bulletin/article/abs/nanostructured-cerium-oxide-ecocatalysts/594109B60740890F69FE5642D0553563)
13. [Construction of cerium-based oxide catalysts with abundant defects/vacancies, J. Mater. Chem. A 11 (2023) 19210](https://pubs.rsc.org/en/Content/ArticleLanding/2023/TA/D3TA03310D)
14. [Critical Materials Strategy, U.S. Department of Energy (2011), cerium profile](https://www.energy.gov/documents/doecms2011finalfullpdf)
15. [USGS Open-File Report 2011-1189, rare earth elements slide set](https://pubs.usgs.gov/of/2011/1189/of2011-1189.pptx.pdf)
16. [A review on chemical and mechanical phenomena at the wafer interface during chemical mechanical planarization, Journal of Materials Research](https://doi.org/10.1557/s43578-020-00060-x)
17. [Rare Earth Elements: End Use and Recyclability, USGS SIR 2011-5094](https://pubs.usgs.gov/sir/2011/5094/pdf/sir2011-5094.pdf)
18. [Microbially mediated cerium oxidation in sea water, Nature 345 (1990) 421](https://www.nature.com/articles/345421a0)
19. [Cerium anomaly as a tracer for paleo-oceanic redox conditions, Frontiers in Earth Science (2022)](https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.927826/full)

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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Elements and inorganic substances › Element classifications and synthetic elements › Transition, platinum-group, and geochemical element sets › Rare earth elements*

*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license