Cerium

Cerium is a <a href="/facts/Chemical_element/0jducgWD">chemical element</a>; it has <a href="/facts/Chemical_symbol/2Fe1VAL0">symbol</a> Ce and <a href="/facts/Atomic_number/bgAr581S">atomic number</a> 58. It is a <a href="/facts/Hardness/PtGn6E20">soft</a>, <a href="/facts/Ductile/SBJsahEk">ductile</a>, and silvery-white <a href="/facts/Metal/pqQVs8QU">metal</a> that tarnishes when exposed to air. Cerium is the second element in the <a href="/facts/Lanthanide/rt3XIRCl">lanthanide</a> series, and while it often shows the <a href="/facts/Oxidation_state/W53W6s6V">oxidation state</a> of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is considered one of the <a href="/facts/Rare-earth_element/PQSUQumk">rare-earth elements</a>. 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 <a href="/facts/Monazite/an71GkIH">monazite</a> and <a href="/facts/Bastn%25C3%25A4site/wSaG43h8">bastnäsite</a> 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 <a href="/facts/Neodymium/GzDkTIoI">neodymium</a>, <a href="/facts/Lanthanum/Uhmmy1sB">lanthanum</a>, and <a href="/facts/Praseodymium/2lnRJ9dH">praseodymium</a>. Its estimated <a href="/facts/Abundance_of_elements_in_Earth%2527s_crust/UDSVHH56">abundance in the Earth's crust</a> is 68 <a href="/facts/Parts_per_million/PozRuoLM">ppm</a>.
Cerium was the first of the lanthanides to be discovered, in <a href="/facts/Bastn%25C3%25A4s/oVVqSJPW">Bastnäs</a>, Sweden. It was discovered by <a href="/facts/J%25C3%25B6ns_Jakob_Berzelius/HakSv3sP">Jöns Jakob Berzelius</a> and <a href="/facts/Wilhelm_Hisinger/09AEPVFQ">Wilhelm Hisinger</a> in 1803, and independently by <a href="/facts/Martin_Heinrich_Klaproth/5DAt7l6Q">Martin Heinrich Klaproth</a> in Germany in the same year. In 1839 <a href="/facts/Carl_Gustaf_Mosander/nlB4bhRp">Carl Gustaf Mosander</a> separated cerium(III) oxide from other rare earths, and in 1875 <a href="/facts/William_Francis_Hillebrand/JqKDg9q6">William Francis Hillebrand</a> became the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, <a href="/facts/Cerium(IV)_oxide/pqmIvGGc">cerium(IV) oxide</a> is used to polish glass and is an important part of <a href="/facts/Catalytic_converter/KsP1ecPY">catalytic converters</a>. Cerium metal is used in <a href="/facts/Ferrocerium/1Hp6Hmqw">ferrocerium</a> lighters for its <a href="/facts/Pyrophoric/1b8Sl2AJ">pyrophoric</a> properties. Cerium-doped <a href="/facts/Yttrium_aluminium_garnet/U6m3FjcR">YAG</a> phosphor is used in conjunction with blue <a href="/facts/Light-emitting_diode/gE8x4MDb">light-emitting diodes</a> to produce white light in most commercial white LED light sources.

Cerium open-in-new

Cerium