Write about Cerium atom?

     

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 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 bastnasite 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 26thmost abundant element, making up 66 ppm of the Earth's crust, half as much as chlorine and five times as much as lead.  Cerium was the first of the lanthanides to be discovered, in Bastnas, Sweden, by Jons Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year.