CERIUM (CAS: 7440-45-1)

Cerium is a chemical element with symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet Ceres (itself named for the Roman goddess of agriculture). Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth’s crust by weight. It is found in a number of minerals, the most important being monazite and bastnäsite. Commercial applications of cerium are numerous. They include catalysts, additives to fuel to reduce emissions and to glass and enamels to change their color. Cerium oxide is an important component of glass polishing powders and phosphors used in screens and fluorescent lamps. It is also used in the “flint” (actually ferrocerium) of lighters.

Chemical properties

Cerium metal tarnishes slowly in air and burns readily at 150 °C to form cerium(IV) oxide:

Ce + O2 → CeO2

Cerium metal is highly pyrophoric, meaning that when it is ground or scratched, the resulting shavings catch fire.

Cerium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form cerium hydroxide:

2 Ce (s) + 6 H2O (l) → 2 Ce(OH)3 (aq) + 3 H2 (g)

Cerium metal reacts with all the halogens:

2 Ce (s) + 3 F2 (g) → 2 CeF3 (s) [white]2 Ce (s) + 3 Cl2 (g) → 2 CeCl3 (s) [white]2 Ce (s) + 3 Br2 (g) → 2 CeBr3 (s) [white]2 Ce (s) + 3 I2 (g) → 2 CeI3 (s) [yellow]

Cerium dissolves readily in dilute sulfuric acid to form solutions containing the colorless Ce(III) ions, which exist as a [Ce(OH2)9]3+ complexes:[9]

2 Ce (s) + 3 H2SO4 (aq) → 2 Ce3+ (aq) + 3 SO42−(aq) + 3 H₂ (g)

The solubility of cerium is much higher in methanesulfonic acid.