Inert Gas: Definition, Types & Examples

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  • 0:01 What is an Inert Gas?
  • 2:09 Why Are Some Gases Inert?
  • 3:45 The Noble Gases
  • 4:09 Other Inert Gases
  • 4:56 Uses
  • 5:38 Lesson Summary
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Lesson Transcript
Cynthia Shonberg

Cynthia has taught high school science courses for many years and has a Master of Science degree and a Master of Arts in Teaching.

Expert Contributor
Maria Airth

Maria has a Doctorate of Education and over 20 years of experience teaching psychology and math related courses at the university level.

In this lesson, we will define the term 'inert gas.' You will also have the opportunity to explore different types of inert gases and the ways in which they are used.

What Is an Inert Gas?

What do a brightly colored flashing neon sign and lofty birthday balloons have in common? Both are filled with an inert gas. An inert gas is a gas that is generally non-reactive with other substances. The term 'inert' means non-reactive. We refer to gases as being chemically inert if their atoms don't combine with other atoms in chemical reactions.

If you are unfamiliar with the term 'inert,' it may make more sense with the following analogy. Let's suppose you are at a party, but you aren't feeling well. You are not up for interacting too much with other people. In this situation, we could say that you are inert because you are not mixing with others at the party. Inert gases behave in a similar way.

As you probably know, matter exists in three states: solid, liquid, and gas. One of the most important properties of gases is that they do not have a fixed volume like solids and liquids. They expand to fit their containers. There are many gases that make up our atmosphere, including inert gases.

When we refer to inert gases, we are usually referring to six primary ones, also called the noble gases. Meet the most common inert gases: helium (He), argon (Ar), neon (Ne), krypton (Kr), xenon (Xe), and radon (Rn). Another noble gas, element 118 (Uuo), does not occur naturally. 'Wait a minute', you think, 'I've heard of krypton! Isn't that the planet that Superman calls home?' It is, according to the comic books, and presumably, the planet got its name from the element.

We find krypton, and the other noble gases in the far right hand column of the periodic table. Many of the noble gases were discovered in the mid to late 1800s. Helium was discovered first, followed by argon. The name argon comes from Greek and means 'inert.' It is important to know that not all inert gases are found in the periodic table because they are molecular gases. These include nitrogen gas (N2) and carbon dioxide (CO2).

Why Are Some Gases Inert?

Atoms are considered to be unstable if they do not have a filled outer orbital. For atoms with an atomic number greater than 5, the 'magic number' for filling the outer orbital is 8. For smaller atoms (atoms with atomic numbers less than 5, like helium), the outermost orbital is filled with 2 electrons.

An electron orbital is the location where electrons reside. Most atoms do not have 8 electrons in this outer orbital so they react with other atoms to form bonds to fill their outer electron orbital. The atomic structure of the noble gases is different from the structure of most atoms because they have a filled outer orbital. Because of this, they are stable and do not 'need' to interact with other atoms. Note that one of the noble gases, helium, is a very small atom and has only 2 electrons in its outermost electron orbital (which is its only orbital). It is stable with this filled outer orbital.

We do have a glitch in our description of what inert means with some of the so-called inert gases. Up until the year 1962, scientists thought that the noble gases never reacted with other substances. In that year, a chemist, Neil Bartlett, performed experiments with xenon and found that it could form a compound with platinum and fluorine.

Bartlett shocked the scientific community with this discovery! As a result of his work, we now know that under certain conditions, some of the atoms of a few of the noble gases do form bonds with other atoms. There are several xenon compounds, a few krypton compounds, and at least one argon compound that react with other substances.

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Additional Activities

Creative Composition to Reinforce Inert Gas Knowledge

Students will create a series of educational cartoons to review the definition of inert gas, as well as reinforce acquired knowledge related to the types of inert gasses and examples of each.


  • Markers, colored pencils, or just soft lead drawing pencils
  • Art paper


  • Students should spend some time reflecting on the information learned in the lesson. In this reflection, students should review:
    • The definition of inert gas.
    • The names of the common noble gasses.
    • The uses of inert gasses.
  • Now, students should think of a series of brief educational cartoons that will give this information to a reader in a fun and entertaining way.
    • Students may want to focus each cartoon on one topic covered in the lesson or;
    • Students may create a story board of cartoons that progress logically through a main theme to give all the information.
  • Students should be as creative as possible with their cartooning design and story-line, while giving the information needed.
  • If possible, students should share their work with others to ensure that the main ideas of the lesson are expressed properly in the cartoons.


  • Imagine a castle scene in which a large audience chamber is filled with different shaped atoms personified with faces and limbs.
  • Along one wall of the audience chamber are a string of thrones.
    • Each throne holds an indeterminate shaped atom with a crown.
    • Each crown carries one of six symbols: He, Ar, Ne, Kr, Xe or Rn.
    • These crowned shapes have faces that look bored and body language that clearly isolated them from the crowd.
  • In the foreground of the image, we see two atoms talking to each other.
    • One says, 'Why are their majesties not mingling with the people?'
    • The other replies, 'They are noble gasses. Everyone knows they're inert!'

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