Cerium

Jai Ganesh · 2025-08-15 17:26:11

Cerium

Gist

Cerium is defined as the most abundant rare-earth metal, constituting about 0.0046 weight % of the Earth's crust, and is industrially relevant primarily for its compounds like cerium dioxide (ceria), which possesses notable redox properties and excellent oxygen mobility.

Beyond automotive uses, cerium is vital in glass polishing, ceramics, steel manufacturing, and solid oxide fuel cells, enhancing performance and durability. It also finds applications in industrial catalytic processes, including the cracking of hydrocarbons and emission reduction in power generation and manufacturing.

It oxidizes readily at room temperature. It can decompose slowly in cold water, and very rapidly in hot water. The metal can be attacked by alkaline solutions, dilute and concentrate acids. When scratched with a knife, the pure metal of cerium may ignite.

Summary

Cerium is a chemical element; it has symbol Ce and atomic number 58. It is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is considered one of the rare-earth elements. Cerium has no known biological role in humans but is not particularly toxic, except with intense or continued exposure.

Despite always occurring in combination with the other rare-earth elements in minerals such as those of the monazite and bastnäsite groups, cerium is easy to extract from its ores, as it can be distinguished among the lanthanides by its unique ability to be oxidized to the +4 state in aqueous solution. It is the most common of the lanthanides, followed by neodymium, lanthanum, and praseodymium. Its estimated abundance in the Earth's crust is 68 ppm.

Cerium was the first of the lanthanides to be discovered, in Bastnäs, Sweden. It was discovered by Jöns Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year. In 1839 Carl Gustaf Mosander separated cerium(III) oxide from other rare earths, and in 1875 William Francis Hillebrand became the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, cerium(IV) oxide is used to polish glass and is an important part of catalytic converters. Cerium metal is used in ferrocerium lighters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources.

Details

Cerium (Ce) is a chemical element, the most abundant of the rare-earth metals.

Commercial-grade cerium is iron-gray in colour, silvery when in a pure form, and about as soft and ductile as tin. It oxidizes in air at room temperature to form CeO2. The metal slowly reacts with water, and it quickly dissolves in diluted acids, except hydrofluoric acid (HF) that leads to the formation of the protective fluoride (CeF3) layer on the surface of the metal. Cerium turnings (from when the metal is filed, ground, or machined) easily self-ignite in air, burning white-hot. Its pyrophoric nature accounts for one of its important metallurgical applications in lighter flints. The metal should be stored either in vacuum or in an inert atmosphere. The metal is a moderately strong paramagnet both below and above room temperature and becomes antiferromagnetic below 13 K (−260 °C, or −436 °F). It becomes superconducting in the millikelvin range at pressures exceeding 20 kbar.

Cerium as the oxide (ceria) was discovered in 1803 by Swedish chemists Jöns Jacob Berzelius and Wilhelm Hisinger, working together, and independently by German chemist Martin Klaproth. It was named after the asteroid Ceres, which was discovered in 1801. Cerium occurs in bastnasite, monazite, and many other minerals. It also is found among the fission products of uranium, plutonium, and thorium. Cerium is about as abundant as copper and nearly three times as abundant as lead in the igneous rocks of Earth’s crust.

Four isotopes occur in nature: stable cerium-140 (88.45 percent) and radioactive cerium-142 (11.11 percent), cerium-138 (0.25 percent), and cerium-136 (0.19 percent). Excluding nuclear isomers, a total of 38 radioactive isotopes of cerium have been characterized. They range in mass from 119 to 157 with half-lives as short as 1.02 seconds for cerium-151 and as long as 5 × {10}^{16}years for cerium-142.

The metal is prepared by electrolysis of the anhydrous fused halides or by metallothermic reduction of the halides with alkali or alkaline-earth metals. It exists in four allotropic (structural) forms. The α-phase is face-centred cubic with a = 4.85 Å at 77 K (−196 °C, or −321 °F). The β-phase forms just below room-temperature and is double close-packed hexagonal with a = 3.6810 Å and c = 11.857 Å. The γ-phase is the room temperature form and is face-centred cubic with a = 5.1610 Å at 24 °C (75 °F). The δ-phase is body-centred cubic with a = 4.12 Å at 757 °C (1,395 °F).

Cerium compounds have a number of practical applications. The dioxide is employed in the optics industry for fine polishing of glass, as a decolourizer in glass manufacturing, in petroleum cracking catalysts, and as a three-way automotive emission catalyst that makes use of its dual valence (3+/4+) characteristics. Together with the other rare-earth metals, cerium is a constituent of numerous ferrous alloys to scavenge sulfur and oxygen and to nodulize cast iron. It is also used in nonferrous alloys, most commonly to improve high-temperature oxidation resistance of superalloys. Misch metal (typically 50 percent cerium, 25 percent lanthanum, 18 percent neodymium, 5 percent praseodymium, and 2 percent other rare earths) is primarily used for lighter flints and alloying additions.

Along with praseodymium and terbium, cerium is different from the other rare earths in that it forms compounds in which its oxidation state is +4; it is the only rare earth that exhibits a +4 oxidation state in solution. Salts of the Ce4+ ion (ceric salts), which are powerful but stable oxidizing agents, are used in analytical chemistry to determine oxidizable substances such as ferrous iron (iron in the +2 oxidation state). Cerium in its +3 oxidation state behaves as a typical rare earth.

Element Properties

atomic number : 58
atomic weight : 140.116
melting point : 798 °C (1,468 °F)
boiling point : 3,443 °C (6,229 °F)
specific gravity : 6.7704 (24 °C, or 75 °F)
oxidation states : 3, +4.

Additional Information:

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.

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#1 2025-08-15 17:26:11

Cerium

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