Cerium Information
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Cerium Element
Cerium is a chemical element
with the symbol Ce and atomic number 58. Cerium is a soft, ductile and
silvery-white metal that tarnishes when exposed to air, and it is soft enough
to be cut with a knife. Cerium is the second element in the lanthanide series,
and while it often shows the +3 oxidation state characteristic of the series,
it also exceptionally has a stable +4 state that does not oxidize water. It is
also considered one of the rare-earth elements. Cerium has no biological role
in humans and is not very toxic.
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. It is the most common of the lanthanides, followed by
neodymium, lanthanum, and praseodymium. It is the 26th-most abundant element,
making up 66 ppm of the Earth's crust, half as much as chlorine and five times
as much as lead.
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.
Cerium was the first of the
lanthanides to be discovered, in Bastnäs, Sweden, 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 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..
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