(also Caesium)



Name Cesium
Symbol Cs
Atomic Number 55
Atomic Mass 132.9054519 atomic mass units
Number of Protons 55
Number of Neutrons 78
Number of Electrons 55
Melting Point 28.5 C
Boiling Point 678.4 C
Density 1.837 grams per cubic centimeter
Normal Phase Solid
Family Alkali Metals
Period 6
Cost $30 per gram



Origin of Name From the Latin caesius, meaning sky blue for the blue lines in its spectrum
Date and Place of Discovery In 1860 in mineral water in Germany
Discovered by Robert Bunsen and Gustav Kirchhoff
Common Compounds
Interesting facts
  • It is soft and ductile.
  • It is the least abundant of the five non-radioactive alkali metals.
  • It is one of the heavier alkali metals.
  • It is very reactive.
  • It is highly explosive when exposed to water.
  • It is found at Bernic Lake in Manitoba, Canada.
Common Uses
  • Drilling fluids for the oil industry.
  • Atomic clocks
  • Nuclear power industry
  • Photoelectric cells
  • Catalyst in the hydrogenation of organic compounds
  • Cancer treatments
  • Magnetometers
  • Infrared flares
  • Ion propulsion systems
  • Spectrophotometry


Photo Courtesy of About.com
Chemical Elements
Jefferson Labs
Mrs. Purdy's Web Page

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