Cesium
Caesium (or cesium) is the chemical element with the atomic number 55 on the periodic table. Its symbol is Cs.
Caesium is an alkali metal. Its melting point is low (28 °C). It is extremely reactive. Because of its high reactivity, it is a dangerous chemical. It may set itself on fire (ignite) in air. It explodes on contact with water. It reacts more violently than the other alkali metals with water. Because of this, caesium is stored in mineral oil.
Caesium is a rare element. Since there is little caesium on the Earth, it is rather expensive. The human body does not need caesium. In large amounts, its chemical compounds are mildly poisonous because it is close to potassium, which the body does need.
History
Caesium was first described in 1860, by Gustav Robert Kirchhoff and Robert Wilhelm Bunsen. They were testing mineral water, from Bad Dürkheim in Rhineland-Palatinate. After they separated calcium, strontium, magnesium and lithium, they saw two lines in the “blue” range of the spectrum. Because of these lines, they concluded that in addition to the elements already found, there must be another unknown substance in the mineral water. They named this substance caesium, after the color blue.
Isotopes and compounds
Caesium has at least 39 known isotopes ranging in atomic mass from 112 to 151. Only one of these, 133Cs, is stable. Therefore, the naturally-occurring isotope of caesium is 133Cs, which is not radioactive. 133Cs is used in atomic clocks, its vibration frequency used to define the length of the second. Another isotope, 137Cs is not made naturally but is made after nuclear fission has been done. It is very radioactive and used as an industrial gamma ray source.
Caesium forms compounds with many other chemical elements. Caesium formate is used in oil drilling because of its high density.
Reactivity
Caesium is extremely reactive in air and water. Caesium rapidly oxidizes in air and can spontaneously combust (randomly catch on fire) at any moment. For this reason, it must be stored in kerosene or a mineral oil, like other group one elements (lithium, sodium, rubidium, and francium.) In water, caesium violently reacts to make caesium hydroxide (2CsOH). The Caesium sinks for about one second, then explodes. The explosion is over 50 times the size of the element dropped in the water, and the explosion is enough to break a common Pyrex beaker, flask, or test tube.
Written for younger readers
Cesium, in simpler words
This version comes from Wikijunior, a set of books written for children aged 8 to 11. It is shorter and uses plainer language than the article above.
From Wikijunior: The Elements
NOTOC
Cesium is a silvery-gold color. It is a soft alkali metal, with a very low melting point — 28C, which is below human body temperature (37C).
It was discovered in 1860 by two German chemists, Robert Bunsen and Gustav Kirchhoff. They discovered it in mineral water from a spa in Germany, using a spectroscope — which they had discovered the previous year.
Did You Know?
- It is liquid at or near room temperature.
- It has been widely used in highly accurate atomic clocks.
- The largest application of cesium has been as cesium formate for drilling fluids Bunsen and Kirchhoff named this element after the color of the light they observed from it with their spectroscope. The Latin word caesius means bluish-gray.
Cesium plays a role in getting oil to run your car and power your home. It can be used in some forms of oil drilling, acting as a lubricant and maintaining pressure.
Cesium binds well with oxygen and other gases, so it is also helpful in making vacuum tubes in order to remove the remaining oxygen from the tubes.
When used as a coating on cathode tubes, it can increase the electric current.
Cesium burns when it comes in contact with the air and vigorously explodes when exposed to water.
Where this page comes from
The article above is adapted from “Cesium” on Simple English Wikipedia, by its contributors. We removed reference markers, navigation boxes and tables, expanded measurement templates into readable numbers, and kept the prose otherwise intact. The simpler version is adapted from Wikijunior on Wikibooks.
Both sources are published under CC BY-SA 4.0, so this page is published under the same licence. You may share and adapt it, including commercially, as long as you credit the original and keep the same licence.
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