Why is cesium explosive


Author: H. Lohninger

Atomic number55
CAS no.7440-46-2
Atomic weight132.9054519 amu
Electron configuration[Xe] 6s1
Melting point28.5 ° C
boiling point671 ° C
density1,880 g / cm3
Sources: Enghag 2004 , Wieser 2011

Cesium was discovered in 1860 by R.W. Bunsen and G.R. Kirchhoff discovered in Dürkheimer mineral water. Bunsen enriched it with cesium and rubidium by using the spectral analysis developed by Kirchhoff. In doing so, he was guided by the intensity of certain spectral lines when fractionating. Elemental cesium was produced by C. Setterberg in 1882 by melting electrolysis of cesium cyanide.

Occurrence and extraction

Cesium, an alkali metal, occurs in nature mostly only as a companion to other alkali salts, or as an impurity in lepidolite. As a mineral, cesium occurs as pollucite (CsAl [SiO3]21/2 H2O) on. One of the richest deposits of cesium can be found in Manitoba, USA.

The metal is produced by reducing cesium hydroxide, CsOH, with magnesium in a hydrogen stream, or with calcium in a vacuum. Furthermore, Cs can be produced by thermal decomposition of cesium azide, or by heating the dichromate with zirconium in a high vacuum. The metallic cesium formed is distilled off:

Cs2Cr2O7 + 2 Zr 2 Cs + 2 ZrO2 + Cr2O3

The historical melt electrolysis of cesium cyanide is only of secondary importance, since cesium is soluble in the electrolyte.
Ref .: Wikimedia Commons, user Dnn87

Cesium has two characteristic, bright, blue lines in the spectrum (hence its name - Latin "caesius" = sky blue). The metal is yellowish-silvery, soft and ductile, and melts at 28.6 ° C. It is much more reactive than potassium and forms cesium hyperoxide (CsO2). Cesium is the least noble of all stable elements and, together with lithium, is on the far left in the electrochemical series.

Cesium, gallium and mercury are the only three metals that are liquid at room temperature. Cesium reacts explosively with cold water, and also reacts with ice above -116 ° C. The resulting cesium hydroxide is the strongest known base and even attacks glass at elevated temperatures (> 300 ° C).


The great affinity of cesium for oxygen enables cesium to be used as a getter material in electron tubes. Cesium is used as a frequency standard in atomic clocks (nuclear resonance of 133Cs isotope at 9192.631770 MHz); by taking appropriate measures, a stability of 10-15 reached, which corresponds to the difference of one second in 30 million years.

Cesium is also used in Cs vapor lamps for night vision devices and as a fuel for ion beam engines. The radioactive one 137Cs (half-life 30.17 years) serves as a radiation source for medical applications in cancer therapy (unfortunately it was also released in large quantities in nuclear power accidents such as in Chernobyl or Fukushima, see also Nuclear reactor in Chernobyl and nuclear reactor in Fukushima).