Cerium
For lighter flints.
Atomic Number: 58
Atomic Symbol: Ce
Atomic Weight: 140.12
Electron Configuration:[Xe]6s^2 4f^1 5d^1History
Cerium was named for the asteroid Ceres, which was discovered in 1801. The element was discovered
two years later in 1803 by Klaproth and by Berzelius and Hisinger. In 1875 Hillebrand and Norton
prepared the metal.
Sources
Cerium is the most abundant so-called rare-earths metal. It is found in a number of minerals including
allanite (also known as orthite), monazite, bastnasite, certie, and samarskite. Monazite and bastnasite are
presently the two more important sources of cerium.
Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil),
allanite (in the western United States), and bastnasite (in Southern California) will supply cerium,
thorium, and the other rare-earth metals for many years to come.
Metallic cerium is prepared by metallothermic reduction techniques, such as reducing cerous fluoride
with calcium, or using electrolysis of molten cerous chloride or others processes. The metallothermic
technique produces high-purity cerium.
Properties
Cerium is especially interesting because of its variable electronic structure. The energy of the inner 4f
level is nearly the same as that of the outer or valence electrons, and only small amounts of energy are
required to change the relative occupancy of these electronic levels. This gives rise to dual valency states.
For example, a volume change of about 10 percent occurs when cerium is subjected to high pressures or
low temperatures. Cesium's valence appears to change from about 3 to 4 when it is cooled or
compressed. The low temperature behavior of cerium is complex.
Cerium