Caesium (Cs)
"Father Time, the most reactive hero, whose atomic vibrations define the second itself."
A memorable persona to anchor Cs in your mind.
1.93
Grams per cm³
28.5
Celsius (°C)
343
Radius (pm)
Daily Life Link
Caesium is found in the atomic clocks that regulate GPS and the internet.
Discovery & History
Year Discovered
1860
Discovered By
Robert Bunsen & Gustav Kirchhoff
Origin of Name
"The name comes from the Latin 'caesius', meaning sky blue, and derived from its flame colour."
Technical Properties
Atomic Mass
132.905 u
Standard State
solid
Boiling Point
671°C
Electron Configuration
[Xe] 6s1
1st Ionization Energy
3.894 eV
Electron Affinity
N/A
Oxidation States
"Caesium is a soft, silvery-gold alkali metal."
Did You Know?
It is considered the most reactive of all the metals on the periodic table; it reacts explosively with water and can ignite spontaneously in air.
The official definition of a second is based on the vibrations of a caesium-133 atom. Caesium atomic clocks are so accurate they would only lose about one second in 300 million years.
Caesium has a silvery-gold appearance and is one of only five elemental metals that are liquid at or near room temperature.
It was the first element to be discovered using a spectroscope, identified by its two bright blue spectral lines. Its name comes from the Latin 'caesius', meaning 'sky-blue'.