Cesium

Atomic number

55

Atomic mass (u)

132.9054520

Category

Alkali metal

Standard state

Solid

Melting point

28.44 °C (301.59 K)

Boiling point

670.85 °C (944 K)

Density (g/cm³)

1.93

Electronegativity (Pauling)

0.79

Electron configuration

[Xe]6s1

Oxidation states

+1

Atomic radius (pm)

343

First ionization energy (eV)

3.894

Discovery & recognition

Discovery year / period (PubChem)

1860

Discovery credited to (RSC)

Gustav Kirchhoff and Robert Bunsen

Date or period recorded by RSC

1860

Discovery place

Heidelberg, Germany

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Caesium is found in the minerals pollucite and lepidolite.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.