Name cesium
Symbol Cs
Atomic Weight 132.90545
Atomic Number 55
CAS ID 7440-46-2
Group Number 1
Group Name Alkali Metal
Period Number 6
Origin of Name Latin, caesius = "sky blue."
Year Discovered 1860
Discovery Credits Discovered by R. Bunsen and G. R. Kirchoff at Heidelberg, Germany.
Class Metallic
Color Silvery gold
Standard State Solid at 77 F & 298 K (Melts slightly above this temperature)
Description Soft, shiny, gold colored metal; reacts rapidly with oxygen and explosively with water. Used as catalyst promoter, in special glasses, and in radiation monitoring equipment. The first element to be discovered spectroscopically and forms the basis for "atomic clocks" because of the ease in which the element is ionized.

Diagnostic tests: 
In solution, a cesium will give a flame test color of a beautiful sky-blue. This flame test will be contaminated with the colors of the other alkaline elements which are present in the sample. You will probably need a diffraction spectroscope to view the two blue emission lines from cesium.

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