โ–ธโ–ธ
  • ๐Ÿ‡ฌ๐Ÿ‡ง Caesium
  • ๐Ÿ‡จ๐Ÿ‡ณ ้Šซ
  • ๐Ÿ‡ณ๐Ÿ‡ฑ Cesium
  • ๐Ÿ‡ซ๐Ÿ‡ท Césium
  • ๐Ÿ‡ฉ๐Ÿ‡ช CŠsium
  • ๐Ÿ‡ฎ๐Ÿ‡ฑ ืฆื–ื™ื•ื
  • ๐Ÿ‡ฎ๐Ÿ‡น Cesio
  • ๐Ÿ‡ฏ๐Ÿ‡ต ใ‚ปใ‚ทใ‚ฆใƒ 
  • ๐Ÿ‡ต๐Ÿ‡น Césio
  • ๐Ÿ‡ท๐Ÿ‡บ ะฆะตะทะธะน
  • ๐Ÿ‡ช๐Ÿ‡ธ Cesio
  • ๐Ÿ‡ธ๐Ÿ‡ช Cesium

Caesium: the essentials

Caesium atoms have 55 electrons and the shell structure is 2.8.18.18.8.1. The ground state electronic configuration of neutral caesium is [Xe].6s1 and the term symbol of caesium is 2S1/2.

Caesium: description  

Caesium is known as cesium in the USA.

The metal is characterised by a spectrum containing two bright lines in the blue (accounting for its name). It is silvery gold, soft, and ductile. It is the most electropositive and most alkaline element. Caesium, gallium, and mercury are the only three metals that are liquid at or around room temperature. Caesium reacts explosively with cold water, and reacts with ice at temperatures above -116°C. Caesium hydroxide is a strong base and attacks glass.

Science and Ink cartoon for caesium
Cartoon by Nick D Kim ([Science and Ink], used by permission).

caesium
Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.

Caesium: physical properties

More physical properties...

Caesium: heat properties

More thermochemical properties...

Caesium: electronegativities

More electronegativity properties...

Caesium: orbital properties

More orbital properties...

Caesium: abundances

More geological data...

Caesium: crystal structure

Cs crystal structure
The solid state structure of caesium is: bcc (body-centred cubic).

More crystallographic data...

Caesium: biological data

Caesium (cesium in USA) has no biological role. However it is capable of replacing potassium in the body to some extent because of its chemical similarity. Ingestion of any caesium compounds is therefore to be avoided. Because of this similarity, the isotopes 134Cs and 137Cs (present in the biosphere in small amounts as a result of radiation leaks) are very toxic. Rats fed caesium in place of potassium in their diet die.

More biological data...

Caesium: uses

Uses...

Caesium: reactions

Reactions of caesium as the element with air, water, halogens, acids, and bases where known.

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Caesium: binary compounds

Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of caesium where known.

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Caesium: compound properties

Bond strengths; lattice energies of caesium halides, hydrides, oxides (where known); and reduction potentials where known.

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Caesium: history

Caesium was discovered by Gustav Kirchhoff, Robert Bunsen in 1860 at Germany. Origin of name: from the Latin word "caesius" meaning "sky blue" or "heavenly blue".

More history...

Caesium: isotopes

Isotope abundances of caesium
Isotope abundances of caesium with the most intense signal set to 100%.

More isotope and NMR data...

Caesium: isolation

Isolation: caesium (cesium in USA) would not normally be made in the laboratory as it is available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative caesium ion Cs+.

Caesium is not made by the same method as sodium as might have been expected. This is because the caesium metal, once formed by electrolysis of liquid caesium chloride (CsCl), is too soluble in the molten salt.

cathode: Cs+(l) + e- → Cs (l)

anode: Cl-(l) → 1/2Cl2 (g) + e-

Instead, it is made by the reaction of metallic sodium with hot molten caesium chloride.

Na + CsCl ⇌ Cs + NaCl

This is an equilbrium reaction and under these conditions the caesium is highly volatile and removed from the system in a form relatively free from sodium impurities, allowing the reaction to proceed. It can be purified by distillation.