Cesium

55
Cs
Group
1
Period
6
Block
s
Protons
Electrons
Neutrons
55
55
78
General Properties
Atomic Number
55
Atomic Weight
132.9054519
Mass Number
133
Category
Alkali metals
Color
Silver
Radioactive
Yes
From the Latin word caesius, sky blue
Crystal Structure
Body Centered Cubic
History
Robert Bunsen and Gustav Kirchhoff were the first to suggest finding cesium in 1860 by spectrum analysis.

They discovered cesium by its two blue emission lines in a sample of Dürkheim mineral water.

The pure metal was eventually isolated by the German chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen.
Electrons per shell
2, 8, 18, 18, 8, 1
Electron Configuration
[Xe] 6s1
Cs
Cesium was the first element discovered using a spectroscope
Physical Properties
Phase
Solid
Density
1.873 g/cm3
Melting Point
301.59 K | 28.44 °C | 83.19 °F
Boiling Point
944.15 K | 671 °C | 1239.8 °F
Heat of Fusion
2.09 kJ/mol
Heat of Vaporization
65 kJ/mol
Specific Heat Capacity
0.242 J/g·K
Abundance in Earth's crust
0.00019%
Abundance in Universe
8×10-8%
Cesium
Image Credits: Wikimedia Commons (Dnn87)
Cesium metal sample from the Dennis s.k collection
CAS Number
7440-46-2
PubChem CID Number
5354618
Atomic Properties
Atomic Radius
265 pm
Covalent Radius
244 pm
Electronegativity
0.79 (Pauling scale)
Ionization Potential
3.8939 eV
Atomic Volume
71.07 cm3/mol
Thermal Conductivity
0.359 W/cm·K
Oxidation States
-1, 1
Applications
The radioactive isotope cesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology.

Cesium is also used in photoelectric cells and as a catalyst in the hydrogenation of organic compounds.

Cesium vapor thermionic generators are low-power devices that convert heat energy to electrical energy.
Cesium compounds are considered to be mildly toxic
Isotopes
Stable Isotopes
133Cs
Unstable Isotopes
112Cs, 113Cs, 114Cs, 115Cs, 116Cs, 117Cs, 118Cs, 119Cs, 120Cs, 121Cs, 122Cs, 123Cs, 124Cs, 125Cs, 126Cs, 127Cs, 128Cs, 129Cs, 130Cs, 131Cs, 132Cs, 134Cs, 135Cs, 136Cs, 137Cs, 138Cs, 139Cs, 140Cs, 141Cs, 142Cs, 143Cs, 144Cs, 145Cs, 146Cs, 147Cs, 148Cs, 149Cs, 150Cs, 151Cs