What is Cesium?

What is implied by the term Cesium? Cesium (Cs) is a compound element with atomic number 55 in the periodic table found by Gustov Kirchhoff and Robert Bunsen in the year 1860. This name has been derived from a Latin word Caesius which means sky blue, as it ignites with blue fire. 

This silvery metal with a golden cast is the most reactive and out of all the metals, one of the softest. The melting point of Cesium is at 28.4 °C (83.1 °F), directly above room temperature. It is about half as abundant as lead and multiple times (70) as abundant as silver. Cesium prevails in minute amounts (7 parts for every million) in Earth's crust in the minerals pollucite, rhodizite, and lepidolite. 



Atomic Number


Atomic Mass

132.9054 g.mol-1

Discovered by

Gustav Kirchchoff and Robert Bunsen in 1860

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Cesium Uses

The following points highlight the applications or uses of the Cesium:

  • Cesium formate-based drilling liquids are widely utilized in the extractive oil industry.

  • It is utilized in thermionic generators, which convert heat energy into electrical energy.

  • As the thickness of Cesium is high, cesium chloride, cesium sulfate are generally utilized in molecular biology.

  • Cesium is utilized in producing optical glasses and other optical instruments. It is used to expel oxygen from lights and vacuum tubes.   

  • Cesium's extraordinary use is that it is utilized in the production of the most exact atomic clock. It is also known as a cesium clock.

Properties of Cesium

The properties of Cesium are explained by dividing them into two main categories. These are:

  1. Physical Properties.

  2. Chemical Properties.

These will be explained one by one as follows:

Physical Properties of Cesium

The physical properties of Cesium are as follows:

  • It is a delicate, silvery- gold alkali element. These are immediately attacked via air and respond violently with water.

  • It is an incredibly unique element and assessed that only three parts for every million are accessible in the Earth's Crust.

  • It is found in minerals like pollucite and lepidolite. Erosion and shrinking of rocks are the common reasons for which they prevail in the environment.

Other Properties can be Made More Transparent with the Help of the Following Chart:





1.89 g/cm3

0.0683 lb/in3

Boiling Point



Melting Point



Chemical Properties of Cesium

As backed up by physical properties, Cesium also depicts various chemical properties. These properties marked their presence in the environment. The following points highlight the chemical features of Cesium:

  • The total number of electrons i.e., Atomic Number in the Cesium is 55

  • As per the periodic table, Atomic Symbol of the Cesium is Cs

  • An average mass or the Atomic weight of the Cesium is 132.90

  • At room temperature, Cesium is robust in nature. 

  • The melting point of the Cesium is 83.3 degrees Fahrenheit.

  • The boiling point of the Cesium is 1240 degrees Fahrenheit.

Chemical Properties can be Glimpsed with the Help of the Following Chart:







Atomic Number


State at 200C


Key Isotopes


Electron configuration


CAS number


ChemSpider ID


ChemSpider is a free chemical structure database.

Interesting Facts about Cesium

There are specific interesting facts about the Cesium. These are:

  • They are not harmful to life and also don’t have any biological importance.

  • There are rarest chances to occur Cesium after getting into contact with radioactive. A person might experience the damage of cells due to the harmful effects of radiation.

  • Cesium is a salt metal, alongside lithium, sodium, potassium, rubidium, and francium. Alkali metals are profoundly reactive, have one electron in their outer shell, and don't happen openly in nature. 

  • Cesium is unimaginably precise at timekeeping and is utilized in atomic clocks. The exact meaning for a second is the time it takes for the cesium atom to vibrate 9,192,631,770 times between energy levels. 

  • Cesium-based atomic clocks lose one second for every 100 million years. 

  • Cesium is one of four metals that are fluid at or close to room temperature; the others are mercury with the melting point of minus 37.9 F, or minus 38.8 C, gallium, and francium. 

  • As per Chemicool, the abundance of Cesium in Earth's outside layer is around 3 parts for every million by weight, and in the nearby solar system 8 parts for each billion by weight.

  • As per the Periodic Table, Cesium is the 50th most common element in Earth's crust. 

  • As Cesium is highly reactive, it combines different elements very quickly, particularly oxygen and various gasses and nonmetals, as indicated by Encyclopedia Britannica.

  • There are two ways of producing radioactive isotopes of the Cesium. The first one is the fission of uranium in fuel rods in nuclear power plants and second by the explosion of nuclear weapons.

FAQ (Frequently Asked Questions)

1. What is the History Behind the Cesium?

Cesium was the first element to be found with a spectroscope. In 1860, German scientific experts found Robert Bunsen and Gustav Kirchhoff when examining the spectrum of mineral water, as per WebElements. 

The first practical applications of Cesium were acknowledged during the 1920s, as per the USGS. Cesium was utilized in vacuum tubes to evacuate traces of residual oxygen because of its prepared nature to bond with it, and as a coating on heated cathodes to build the electric flow.

2. What are the Harmful Effects of Cesium?

Cesium is exposed to humans by breathing, drinking, or eating. In the air, the degrees of Cesium are commonly low. However, radioactive Cesium has been distinguished at some level in surface water and numerous kinds of nourishments.  

The measure of Cesium in nourishments and beverages relies on the emissions of radioactive Cesium through nuclear power plants, mainly through accidents. These accidents have not happened since the Chernobyl disaster in 1986. Individuals that work in the nuclear power industry might be presented to more significant levels of Cesium, however numerous precautionary measurements can be taken to prevent this. 

It isn't likely that individuals experience health impacts that can be identified with Cesium itself.