Discovery date : 1860
Discovered by: Gustav Kirchhoff and Robert Bunsen
Origin of the name: The name comes from the Latin 'caesius',
meaning sky blue, and derived from its flame colour.
Allotropes :
~>CESIUM is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28.5C, which makes it one of only five elemental metals that are liquid at or near room temperature.
| FACT BOX | |||
| Group | 1 | Melting point | 28.5°C, 83.3°F, 301.7 K |
| Period | 6 | Boiling point | 671°C, 1240°F, 944 K |
| Block | s | Density (g cm−3) | 1.873 |
| Atomic number | 55 | Relative atomic mass | 132.905 |
| State at 20°C | Solid | Key isotopes | 133Cs |
| Electron configuration | [Xe] 6s1 | CAS number | 7440-46-2 |
| ChemSpider ID | 4510778 | ChemSpider is a free chemical structure database | |
Caesium was almost discovered by Carl Plattner in 1846 when he investigated the mineral pollucite (caesium aluminium silicate). He could only account for 93% of the elements it contained, but then ran out of material to analyse. (It was later realised that he mistook the caesium for sodium and potassium.)
Caesium was eventually discovered by Gustav Kirchhoff and Robert Bunsen in 1860 at Heidelberg, Germany. They examined mineral water from Durkheim and observed lines in the spectrum which they did not recognise, and that meant a new element was present. They produced around 7 grams of caesium chloride from this source, but were unable to produce a sample of the new metal itself. The credit for that goes to Carl Theodor Setterberg at the University of Bonn who obtained it by the electrolysis of molten caesium cyanide, CsCN.