Caesium is a soft, golden alkali metal whose atomic transition defines the SI second.
Atomic number
55
Category
Alkali metal
Period
6
Group
1
State
Solid
Fun facts about Caesium
It melts near room temperature.
Caesium reacts explosively with water and is sealed from air.
Caesium atomic clocks provide exceptionally stable frequency references.
Common uses of Caesium
Atomic clocks
Oil-well drilling fluids
Photoelectric and scientific instruments
Where Caesium sits in the periodic table
Caesium is classified as a alkali metal in period 6 and group 1 of the periodic table. Under the conditions represented in this reference, its state is solid.
Quick chemistry revision
For quick revision, pair the symbol Cs with atomic number 55 and the listed atomic mass 132.91. The summary, facts, and uses above keep those element properties together in one reference.