Noble Gases: Definition, List & Properties
Elements are grouped on the periodic table based on their chemical properties. In this lesson you will learn about a group of elements known as the noble gases and their unique properties.
Definition of Noble Gases
The periodic table is divided into 18 vertical columns referred to as groups or families. On the far right side of the periodic table in group 18 is a unique group of elements known as the noble gases. The noble gases are a group of extremely nonreactive elements that all exist in the gas state.
They are often considered to be inert. Inertness refers to an element's tendency to resist change and reactions. For this reason, the noble gases were discovered later than many other elements. Scientists did not notice them because they were never found reacting with other elements in nature or in the lab.
List of Noble Gases
The noble gases include helium, neon, argon, krypton, xenon, and radon.
- Helium - This gas has the atomic number two and is the second most abundant element in the universe. It is a main part of most stars.
- Neon - Neon has the atomic number ten and is commonly used in lamps for the red-orange glow it gives off when exposed to electricity.
- Argon - Argon has the atomic number 18. It is most commonly used in welding as an inert gas to reduce the risk of fire and in lighting.
- Krypton - This gas has atomic number 36 on the periodic table and is most commonly used in photography and lighting.
- Xenon - Xenon has atomic number 54. It is most commonly used in lamps and has been used as an anesthetic.
- Radon - Radon is atomic number 86. It is formed by the radioactive decay of other elements and leeches up to the surface of Earth as it is formed. It is known to cause lung cancer when breathed in by those who encounter the gas on a regular basis.
Properties of Noble Gases
Noble gases share many unique properties when compared to other elements. They are all odorless, colorless nonmetals. All of the noble gases have full shells of valence electrons. Electrons are the subatomic particles that are responsible for many of the reactions of elements. Elements gain, lose, or share these electrons to form compounds. Since the noble gases have the exact full amount of these electrons, they are not interested in forming compounds or reacting with other elements - this leads to their inertness. Noble gases are monatomic. This means they occur in nature as single atoms rather than in pairs as many other elements are found.
Because they are odorless and colorless, many of the tests commonly used by chemists to identify elements do not work. However, the noble gases do respond to electric currents by emitting specific colors of light. This enables scientists to identify the gas by shooting electricity through it and observing the color given off by the gas. This property is also the reason that many noble gases are commonly used in lighted signs. Many signs are called neon signs, but they do not necessarily contain neon. Depending on the color needed, they can contain any of the noble gases.
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