What is Cesium? - Uses, Facts & Properties

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

In this lesson, we will learn about cesium and its properties as an element. We will learn how it was discovered, how it is used today, and about radioactive-cesium, then you can test your knowledge with a quiz.

What is Cesium?

Think back to a typical science fiction movie that depicts a radioactive substance. It is typically shown as a silvery liquid that is shiny and kind of runny. This is how cesium appears. Cesium is one of only five elemental metals that are liquid at room temperature (or close to room temperature). Since cesium can be radioactive, the substances depicted in such science fiction movies might just be cesium!

Cesium is a chemical element. It is classified as an alkali metal and has the atomic number 55. Even when in solid form, it is still a fairly soft solid. It will react with common compounds such as oxygen and water to form compounds that can be useful in industry. Cesium is not found widely on the planet - in just three parts per million in the earth's crust.

Cesium has a silvery-gold color
An image of cesium

Cesium: A Brief History

Cesium was discovered in 1860 by two German scientists, Gustav Kirchhoff and Robert Bunsen. It was the first element to be discovered via spectroscopic analysis, which allows one to view each element in a specific color. Cesium displays a bright blue color, hence the name - it comes from the Latin word caesius, which means 'sky blue.'

This element was first seen when the two scientists analyzed mineral water spectroscopically. Its first use was in vacuum tubes - when it is combined with oxygen, the resulting compound removes trace gases from vacuum tubes so that the vacuum can properly operate.

Uses of Cesium Today

Today, cesium is still not widely used. Its most common application is in the oil industry. Cesium can be utilized during oil drilling to help maintain pressure. In the form used, it is not toxic to the environment and so clean-up is easy and safe. It also has applications in several electronics, such as the gamma ray detector, and it is still commonly used in creating vacuum tubes.

Radioactive Cesium

Cesium can form radioactive isotopes. An isotope is a secondary structure of an element. It is still cesium, but it is missing an electron or proton. The most common radioactive isotope of this element is cesium-137, which is not found naturally but is formed in nuclear reactors and nuclear weapons via beta-decay. This occurs by the cesium gaining a proton and losing a neutron.

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