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What are Inert Gases?

Members of group 18 in the modern periodic table are known as noble gases. They are colourless, odourless gases at room temperature, isolated by William Ramsay in 1898 from the air.

Inert Gases are:

  1. Helium (He)
  2. Neon (Ne)
  3. Argon (Ar)
  4. Krypton (Kr)
  5. Xenon (Xe)
  6. Radon (Rn)

Group-18: Inert Gases | Chemistry Class 12 - NEET

The members of the group have eight electrons in their outermost orbit (except helium which has two electrons). Thus, they have a stable configuration. Group 18 elements are gases and chemically unreactive, which means they don’t form many compounds. Thus, the elements are known as inert gases. Like the other group elements, noble gas elements also exhibit trends in their physical and chemical properties. The general characteristics of noble gases are discussed below.


General/Physical Characteristics of Group 18 Elements:

  1. Electronic configuration: 

    Their valence shell electronic configuration is nsnpexcept He.
    Group-18: Inert Gases | Chemistry Class 12 - NEET
  2. Physical state: 

    They are all gases under ordinary conditions of temperature and pressure.
  3. Abundance: 

    In 1.0% air, the abundance follows the order: Ar > Ne > He > Kr > Xe
  4. Atomicity: 

    The Cp/Cv = 1.67 shows their monoatomic nature.
    However, under high energy conditions, several molecular ions such as He+, HeH+, HeH2+and Ar2+ are formed in discharge tubes. They only survive momentarily and are detected spectroscopically.
  5. Melting and boiling points: 

    Due to the increase in the magnitude of Van der Waals’ forces, the melting point and boiling point increase from He to Rn.
  6. Atomic radii: 

    The atomic radii increase from He to Rn. It corresponds to the Van der Waals’ radii. So it has the greatest atomic size in the respective period.
  7. Density: 

    The density of noble gases increases down the group.
  8. Heat of vaporisation: 

    They have very low values of heat of vaporisation due to weak Van der Waals’ forces of attraction. The value increases down the group.
  9. Solubility in water: 

    They are slightly soluble in water and solubility increases from He to Rn.
  10. Liquefication: 

    It is extremely difficult to liquefy inert gases due to weak Van der Waals’ forces of attraction among their molecules. Hence, they possess a low value of critical temperature also.
  11. Ionisation energy: 

    All noble gases possess a very stable (ns2 and ns2 np6) electronic configuration. Therefore, the ionisation energy of noble gases is very high and decreases down the group.
  12. Electron affinity: 

    Due to the presence of stable electronic configuration, they have no tendency to accept an additional electron. Therefore, electron affinity is almost zero.

Chemical Properties of Group 18 Elements:

The noble gases are inert in nature because of their completely filled subshells. In 1962, the first compound of noble gases was prepared. It is hexafluoroplatinate (prepared by Bartlett).

Xe + PtF6 → Xe[PtF6]

Now, many compounds of Xe and Kr are known with fluorine and oxygen.


Preparation of Compounds of Xenon:

Group-18: Inert Gases | Chemistry Class 12 - NEET

Chemical Reactions of Xenon Compounds:

Group-18: Inert Gases | Chemistry Class 12 - NEET

Group-18: Inert Gases | Chemistry Class 12 - NEET

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FAQs on Group-18: Inert Gases - Chemistry Class 12 - NEET

1. What are inert gases?
Ans. Inert gases, also known as noble gases, are a group of chemical elements found in Group 18 of the periodic table. These elements include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). They are called inert gases because they are highly stable and do not easily react with other elements.
2. What are the general/physical characteristics of Group 18 elements?
Ans. Group 18 elements, or inert gases, have several general/physical characteristics. They are all colorless, odorless, and tasteless gases. They have low boiling and melting points, which means they exist as gases at room temperature. They are also nonflammable and have low densities. Additionally, they have a stable electron configuration with a full outer shell of electrons.
3. What are the chemical properties of Group 18 elements?
Ans. The chemical properties of Group 18 elements mainly revolve around their high level of stability due to their full outer electron shell. They have very low reactivity and are considered to be chemically inert. In fact, they are the least reactive elements in the periodic table. They do not readily form compounds with other elements and are often used in applications where their inertness is beneficial, such as in light bulbs and lasers.
4. How are Group 18 elements used in everyday life?
Ans. Group 18 elements have several everyday life applications. Helium, for example, is commonly used to fill balloons and airships due to its low density. It is also used in cryogenic applications and as a coolant in nuclear reactors. Neon is used in neon signs and fluorescent lights, while argon is used in welding and as a protective gas in the production of metals. Krypton and xenon are used in various lighting applications, including high-intensity discharge lamps and flash photography.
5. What are some important properties of radon, an inert gas?
Ans. Radon, the heaviest element in Group 18, is a radioactive gas. It is colorless, odorless, and tasteless, making it difficult to detect without proper instruments. Radon is formed through the decay of uranium and thorium in rocks and soil, and it can seep into homes and buildings through cracks and gaps in the foundation. Radon is considered a health hazard as prolonged exposure to high levels of radon gas can increase the risk of lung cancer.
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