Xenon Barium

Cesium (Cs)

From Wikipedia, the free encyclopediaCaesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium.

Cesium in the periodic table

Symbol

Atomic number

Group

Period

Block

Element category

Alkali Metal

Physical properties

Phase at STP

Solid

Density

1.93 g/cm³

Atomic weight

132.905 u

Melting point

301.7 K
28.55 °C
83.39 °F

Boiling point

944 K
670.85 °C
1239.53 °F

Atomic properties

Electronegativity (Pauling Scale)

0.79

Electron affinity

45.505 kJ/mol

Oxidation states

−1, +1
(a strongly basic oxide)

Ionization energies

1	375.7 kJ/mol
2	2234.3 kJ/mol
3	3400 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)

[Xe] 6s¹

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹

Electrons per shell

2, 8, 18, 18, 8, 1

History

Discovered

1860

Discovered by

Robert Bunsen
Gustav Kirchhoff