 Discovery Information
|
| Who: Gustov Kirchoff, Robert Bunsen |
| When: 1860 |
| Where: Germany |
|
| Name Origin
|
| Latin: caesius (sky blue); its salts turn flames blue. |
| "Caesium" in different languages. |
|
| Sources
|
| Found in pollucite and as trace in lepidolite (KLi2Al(Al,Si)3O10(F,OH)2). World production is around 20 tons per year.
|
|
| Abundance
|
| Universe: 0.0008 ppm (by weight) |
| Sun: 0.008 ppm (by weight) |
| Carbonaceous meteorite: 0.14 ppm |
| Earth's Crust: 3 ppm |
| Seawater: 3 x 104 ppm
|
| Human: |
| 20 ppb by weight |
| 1 ppb by atoms |
|
| Uses
|
| Used as a 'getter' to remove air traces in vacuum tubes. Since it ionizes readily, it is used as an ion rocket motor propellant. Also used in photoelectric
cells, atomic clocks, infrared lamps.
|
| Radioactive isotopes of caesium are used in the medical field to treat certain types of cancer.
|
| This metal is also used in photoelectric cells due to its ready emission of electrons.
|
|
| History
|
| Caesium (Latin caesius meaning "sky blue" or "light blue") was spectroscopically discovered by Robert Bunsen and Gustav Kirchhoff in 1860 in mineral water from Durkheim, Germany. Its identification was based upon the bright blue lines in its spectrum
and it was the first element discovered by spectrum analysis. The first caesium metal was produced in 1882 by Carl Setterberg.
Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical
applications.
|
|
| Notes
|
| Also know as cesium in the United States. |
| Along with gallium, francium and mercury, caesium is among the only metals that are liquid at or near room temperature.
|
| Caesium has at least 39 known isotopes which is more than any other element, except francium. Although only one of these is naturally occurring and stable, Cs-133.
|
| Caesium is most notably used in atomic clocks, which are accurate to seconds in many thousands of years. SI defines the second
as (exactly) 9,192,631,770 cycles of the radiation which corresponds to the transition between two energy levels of the ground state of the 133Cs atom.
|
|
| Hazards
|
| Caesium is considered highly toxic. Caesium reacts explosively in cold water and also reacts with ice at temperatures above
-116°C.
|
| Caesium is highly flammable in powder form. |
