Caesium or cesium

Symbol: Cs
Atomic number: 55
Category: alkali metals
Group: 1
Period: 6
Block: s
Atomic weight: 132.9054519 g/mol
Electrons per shell: 2, 8, 18, 18, 8, 1
CAS number: 7440-46-2
Phase: solid
Density: 1.93 kg/l (near room temperature)
Melting point: 301.59 K (28.44C, 83.19F)
Boiling point: 944 K (671C, 1240F)
Crystal structure: body centered cubic
Oxidation states: 1
Electronegativity: 0.79 (Pauling scale)
Name's origin: caesius
Name's meaning: blueish grey, as its identification based upon the bright blue lines in its spectrum
Facts:
- it was the first element discovered by spectrum analysis
- is most notably used in atomic clocks
- the most widespread use of caesium today is in caesium formate-based drilling fluids for the oil industry
- radioactive isotopes of caesium are used in the medical field to treat certain types of cancer