CAS Number7440-30-4
PubChem CID23961
Atomic Radius176
Atomic Volume18.1
Atomic Weight168.934
Boiling Point1,950
Bulk Modulus
Crystal StructureSimple Hexagonal
Covalent Radius190
Electrical Resistivity
Electron Configuration[Xe] 4f13 6s2
Electrons per shell2, 8, 18, 31, 8, 2
Heat of Fusion16.8
Heat of Vaporization250
Ionization Potential6.184
Magnetic Ordering
Magnetic Susceptibility
Mass Number69
Melting Point1,545
Atomic Number169
Oxidation States2, 3
Poisson Ratio
Shear Modulus
Specific Heat Capacity0.16
Thermal Conductivity0.168
Van der Waals radius
Young's Modulus
Abundance in Earth's crust0.000045%
Abundance in Universe1×10-8%
Tm Thulium 69 168.93421 6 f 69 1545.0 1950.0 [Xe] 4f13 6s2 2 8 18 31 8 2 9.32 0.000045% Silver Hexagonal 1.3 {"1":"596.7","2":"1160","3":"2285","4":"4120"} 597 50 +3,2 1.77 18.1 16.8 191.0 0.16 16.8 56.K 0 Solid, Paramagnetic, Conductor, Lanthanide, Stable, Natural THOO-li-em Soft, malleable, ductile, silvery metal Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment. Found with other rare earths in the minerals gadolinite, euxenite, xenotime, and monazite. Monazite is often 50% rare earth by weight and 0.007% thulium. CQFDIZfMPVQ Thulium
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. From the Latin word caesius, sky blue 69 1879 Per Theodore Cleve Sweden Named after "Thule", an ancient name for Scandinavia

Isotopes of Cesium

Standard Atomic Weight


Stable Isotopes


Unstable Isotopes

145Tm 146Tm 147Tm 148Tm 149Tm 150Tm 151Tm 152Tm 153Tm 154Tm 155Tm 156Tm 157Tm 158Tm 159Tm 160Tm 161Tm 162Tm 163Tm 164Tm 165Tm 166Tm 167Tm 168Tm 170Tm 171Tm 172Tm 173Tm 174Tm 175Tm 176Tm 177Tm 178Tm 179Tm

Cesium compounds are considered to be mildly toxic
Cesium was the first element discovered using a spectroscope
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.