ChemSphere
58Ce140.116

Cerium

Lanthanide · Period 6 · f-block

The most common rare earth, from lighter sparks to polished glass

Atomic mass
140.116 u
State at 25 °C
Solid
Electronegativity
1.12
Melting point
794.9 °C
Boiling point
3,442.9 °C
Configuration
[Xe] 4f1 5d1 6s2
Building atom…
58 protons 82 neutrons 58 electrons

Nucleus drawn at reduced count for clarity. Drag to rotate.

Cerium, explained

Video lesson in production

Bhavya’s explainer for this element will play here.

Overview

Cerium is a soft, ductile, iron-grey lanthanide and the most abundant of the rare earth elements, about as common in the crust as copper. Its configuration is [Xe] 4f1 5d1 6s2. Like the other lanthanides it readily forms Ce^3+, but it is unique in also having a stable +4 state: losing a fourth electron empties the 4f subshell and leaves the xenon configuration. Ce^4+ is a strong oxidizing agent, used in titrations and organic synthesis, and the ease of switching between +3 and +4 underlies most of cerium's practical uses.

Cerium dioxide is the most effective compound known for polishing glass: it reacts chemically with the glass surface while grinding it, giving optical lenses and phone screens their flawless finish. In catalytic converters, ceria acts as an oxygen buffer, releasing oxygen when exhaust is fuel-rich and absorbing it when lean. Cerium metal is pyrophoric: scraping it sheds tiny particles that ignite in air. Mixed with iron and other lanthanides as ferrocerium, it produces the sparks in lighters and fire starters. Cerium oxide also absorbs ultraviolet light and decolourises glass.

Discovery

In 1803 Jöns Jacob Berzelius and Wilhelm Hisinger in Sweden, and independently Martin Heinrich Klaproth in Germany, found a new earth in a heavy mineral from Bastnäs, Sweden, now called cerite. Berzelius and Hisinger named the element after the dwarf planet Ceres, discovered two years earlier, which itself was named after the Roman goddess of agriculture. The metal was first isolated in 1875 by William Hillebrand and Thomas Norton.

Where it’s found
Cerium makes up about 60 parts per million of the crust and is extracted from bastnäsite and monazite, mainly in China.
What it’s used for
  • Glass polishing powder
  • Catalytic converters
  • Lighter flints (ferrocerium)
  • UV-absorbing glass
  • Self-cleaning ovens
  • Steel and aluminium alloys
In living things
Cerium has no role in humans and has low toxicity. Like lanthanum, it can serve as a cofactor in methanol dehydrogenase enzymes of some bacteria.
Safety
Cerium metal shavings and powder can ignite spontaneously in air, so it is stored under oil or argon; cerium compounds have low toxicity.

How it compares

Where Cerium sits among all 118 elements on the trends that shape the table.

  • Electronegativity1.12Pauling

    #86 of 100 elements with data

  • Ionization energy534kJ/mol

    #91 of 104 elements with data

  • Atomic radius185pm

    #11 of 95 elements with data

  • Electron affinity55kJ/mol

    #45 of 109 elements with data

  • Density6.77g/cm³

    #67 of 114 elements with data

  • Melting point1,070K

    #63 of 110 elements with data

Density
6.77 g/cm³
Atomic radius
185 pm
Covalent radius
163 pm
Molar heat
26.94 J/(mol·K)
Appearance
silvery white
Discovered by
Martin Heinrich Klaproth

Inside the atom

58 electrons arranged in 6 shells: 2 · 8 · 18 · 19 · 9 · 2.

Orbital diagram

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 4f1 · shorthand [Xe] 4f1 5d1 6s2

  1. 1s2
  2. 2s2
  3. 2p6
  4. 3s2
  5. 3p6
  6. 4s2
  7. 3d10
  8. 4p6
  9. 5s2
  10. 4d10
  11. 5p6
  12. 6s2
  13. 5d1
  14. 4f1

Each box is an orbital holding up to two electrons of opposite spin. Highlighted subshells hold the valence electrons that decide how Cerium bonds.

Ionization energies

Energy to remove each electron in turn, on a log scale. Each electron is harder to remove than the last, because the remaining ones feel more of the nucleus.

Signature reactions

The chemistry Cerium is known for.

  1. Redox · Combustion

    Sparking in air

    Particles scraped from cerium or ferrocerium are hot enough to ignite, burning brilliantly to form cerium dioxide. The glowing fragments are what light a lighter's fuel.

    Ce(s)+O2(g)CeO2(s)

    Conditions: fine particles in air, initiated by friction

  2. Redox · Reversible

    Oxygen storage in catalytic converters

    When exhaust is short of oxygen, ceria gives up some of its lattice oxygen; when oxygen is in excess, Ce2O3 takes it back. This buffering keeps the precious metal catalyst working efficiently.

    4CeO2(s)2Ce2O3(s)+O2(g)

    Conditions: hot exhaust, 300–900 °C

  3. Redox · Analysis

    Cerimetric titration

    Yellow-orange cerium(IV) oxidizes iron(II) and becomes colourless cerium(III). Analysts use this one-electron transfer to measure iron and other reducing agents precisely.

    Ce4+(aq)+Fe2+(aq)Ce3+(aq)+Fe3+(aq)

    Conditions: acidic aqueous solution

Where you’ll meet it

Research

No research on Cerium yet

When Bhavya publishes a project that studies Cerium, it will be linked here.

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