55 132.910

Caesium , Cs

Caesium or cesium (North American) is a chemical element with the symbol Cs and atomic number 55. This element belongs to the alkali metal group and possesses unique characteristics that set it apart. It is a soft silvery-gold alkali metal with a melting point of 28 °C (83 °F), which makes it one of only five elemental metals that are liquid at or near room temperature (others including rubidium, mercury and gallium). This characteristic renders caesium particularly intriguing for various applications. Caesium is also considered the least electronegative element. 

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CsCl Powder -4 Mesh 99.999% PureCesium Chloride
CsCl Powder -4 Mesh 99.9% PureCesium Chloride
CsF Powder -4 Mesh 99.9% PureCesium Fluoride
Cs2S Powder -100 Mesh 99.99% PureCesium Sulphide
Boron Nitride Crucible
Boron Nitride Composite Crucible

Known for its lustrous silvery-gold appearance, caesium possesses intriguing physical and chemical properties that have captivated scientists since its discovery. German chemist Robert Bunsen and physicist Gustav Kirchhoff first identified caesium in 1860 through the innovative technique of flame spectroscopy, marking a significant milestone in the understanding of elemental chemistry.

Since the 1990s, caesium's usage has expanded, with its largest application being in the form of caesium formate for drilling fluids. Beyond this, caesium finds its way into the production of electricity, electronics, and various chemical processes. The radioactive isotope caesium-137, with a half-life of about 30 years, is extensively employed in medical applications, industrial gauges, and hydrology, albeit with careful consideration due to its potential health and environmental risks.

Despite its utility, caesium demands cautious handling due to its reactive nature, especially its tendency to react explosively with water. Both nonradioactive caesium compounds and its radioactive isotopes pose significant health and environmental hazards if mishandled, warranting adherence to strict safety protocols.

Caesium stands as a testament to scientific ingenuity, offering a unique blend of properties used for industrial applications.

Symbol Cs
Atomic number 55
No. of naturally occurring isotopes 1
Atomic weight 132.9054
Electronic configuration [Xe] 6s1
Ionization energy/kJmol-1 375.6
Metal radius/pm 265
Ionic radius (6-coordinate)/pm 167
Density (25°C)/gcm-3 1.9
Melting point / °C 28.5
Boiling point / °C 705
ΔHfus/kJmol-1 2.09
ΔHvap/kJmol-1 67
ΔHf(monoatomic gas)/kJmol-1 79
Eo(M+(aq)+e- →M(S))/V -2.92
Temperature (oC) @Vap. Pressure
10-8 Torr -16
10-6 Torr +22
10-4 Torr +30
Electron Beam -
Crucible Quartz
Coil -
Boat Stainless Steel