Cerium (Ce)

Cerium (symbol Ce) is the chemical element with atomic number 58: a lanthanide (rare earth), solid at 0 °C, with an atomic mass of 140.12 u. Discovered in 1803 (Jöns Jacob Berzelius and Wilhelm Hisinger).

Cerium is the most common of the lanthanides, roughly as abundant as copper in Earth's crust. It switches easily from one oxidation state to another, which makes it an excellent “oxygen sponge” in catalytic converters. Scrape it and it bursts into flame: that's the secret of lighter flints.

Key facts

Atomic number: 58
Symbol: Ce
French name: Cérium
Atomic mass: 140.12 u
Molar mass: 140.12 g/mol
Family: Lanthanides
Position: period 6, f-block
State at 0 °C: Solid
Melting point: 794.9 °C
Boiling point: 3,442.9 °C
Density: 6.77 g/cm³
Electronegativity (Pauling): 1.12
First ionization energy: 534 kJ/mol
Atomic radius: 185 pm
Electron configuration: [Xe] 4f¹ 5d¹ 6s²
Abundance in Earth's crust: 66.5 ppm (25th most abundant element)
Indicative price: 5 $/kg (order of magnitude)
Radioactive: no
Discovery: 1803, Jöns Jacob Berzelius and Wilhelm Hisinger

Origin of the name

From the asteroid Ceres.

What does cerium look like?

A soft, ductile, silvery-gray metal that oxidizes quickly in air. A single scratch tears off shavings that ignite in showers of sparks.

Where is cerium found?

About 60 to 66 ppm of Earth's crust, making it the 25th most abundant element. It often accounts for nearly half the rare earths in bastnäsite and monazite.

Natural sources

Bastnäsite
Monazite
Allanite
Cerianite

How is cerium produced?

Unlike its neighbors, cerium can be oxidized to the +4 state, which makes it far less soluble: it's the only lanthanide that can be separated fairly simply from the rest, by oxidation and precipitation. The metal is produced by electrolysis of the molten chloride.

Top producers

China
United States
Myanmar
Australia

What is cerium used for?

Cerium oxide for polishing glass, screens and lenses.
Catalytic converters, where it stores and releases oxygen.
Ferrocerium in lighter flints and fire starters.
Decolorizing and tinting glass, UV protection.
Self-cleaning oven linings.

In everyday life

A lighter flint or camping fire starter
A car's catalytic converter
A smartphone screen polished with cerium oxide
A self-cleaning oven

Role in living things

No role in humans. Like lanthanum, it is used by certain methanol-eating bacteria. Cerium nitrate is occasionally used in a cream for severe burns.

Hazards of cerium

Low toxicity, but the metal as powder or shavings is pyrophoric: it can catch fire on its own. Cerium fires must never be put out with water.

Cosmic origin

Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).
Neutron stars: Created when two neutron stars collide — the “forge” of gold.

History of cerium

Discovered in 1803 simultaneously by Jöns Jacob Berzelius and Wilhelm Hisinger in Sweden and by Martin Heinrich Klaproth in Germany. It was named after Ceres, the first asteroid, spotted two years earlier. In 1903 the Austrian Carl Auer von Welsbach patented the iron-cerium alloy used in lighter flints.

Did you know?

Cerium was named after an asteroid, Ceres, now classified as a dwarf planet.
Auer von Welsbach's gas-lamp mantles contained about 1% cerium oxide, which gave them their brilliant white glow.
Most flat glass and screens are polished with cerium oxide powder.

Isotopes of cerium

Cerium has four stable isotopes, with cerium-140 alone making up nearly 90% of the total. Its radioactive isotopes 141 and 144 are common fission products in reactors.

cerium-136: 0.186% of natural cerium, stable
cerium-138: 0.251% of natural cerium, stable
cerium-140: 88.449% of natural cerium, stable
cerium-141: radioactive, half-life 32.5 days
cerium-142: 11.114% of natural cerium, stable
cerium-144: radioactive, half-life 285 days. An abundant fission product that rained down over Europe after Chernobyl.

Related elements

Same family (lanthanides): Lanthanum (La), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu).