Characteristics Of Group 18 Elements

The group 18 elements include helium, argon, krypton, neon, xenon, and radon. In the outermost orbit, the members of the group possess eight electrons. However, helium has only two electrons. 

Group 18 elements are chemically unreactive and are gases that do not form compounds. They are located in the extreme right of the periodic table and are commonly known as inert gases or noble gases due to their unreactive nature. 

Characteristics of Group 18 Elements

Let us now learn about the characteristics of group 18 elements: 

• They show a stable octet configuration and consist of eight valence electrons in the outermost orbit, except for helium which has a duplet configuration. 
• The atomic radii of the noble gases are very small. As the noble gases increase down the group, the atomic radii increases as well, with an increase in atomic number. 
• The members of group 18 elements display large positive values of electron gain enthalpy.
• All the members of the group, except helium, have eight electrons in their outermost shell and exhibit duplet configuration. Thus, noble gases possess a high ionisation enthalpy.
• As we move down the group, the ionisation enthalpy of noble gases decreases, and there is an increase in the atomic size of group 18 elements.

Physical Properties

The physical properties exhibited by the group 18 elements are mentioned below: 

• These elements exist in a free state due to their stable nature.
• Noble gases are colourless, tasteless, and odourless.
• They are sparsely dissolvable in water.
• Due to the weak Van der Waals force, these gases can be condensed at very low temperatures.
• Helium has the least boiling point among all the members of group 18.

Electronic Configuration of Noble Gases 

The universal configuration of valence shells is given as ns2np6. However, helium is the exception and has the configuration of 1s2.

Chemical Properties

The chemical properties of the noble gases are presented below: 

• Due to the electronic configuration of noble gases, they are chemically latent.
• The elements consist of high ionisation enthalpy and high positive electron gain enthalpy.
• All the group 18 elements are insoluble in water. 
• All the noble gases conduct electricity and fluorescence which is useful to maintain a safe environment.
• Krypton forms krypton difluoride only due to its ionisation enthalpy being higher than xenon.

Uses of Helium

• Since helium is flammable and has a low density, it is used in filling weather balloons and aircraft. It is also useful in cooling down superconducting magnets.
• It is used as a cryogenic agent to conduct low-temperature tests due to its minimal boiling point.
• Helium is used to get the low temperatures for superconductivity liquids.
• It can also be used as stream and cooling gas in gas-fluid chromatography and gas-cooled atomic reactors.
• It is also used in oxygen cylinders, particularly those which are used in sea diving.

Uses of Radon, Argon, Krypton, Xenon, and Neon

• Neon finds its utility in release tubes, where it is used in minute amounts, and bright lighting bulbs, which are used as neon signs.
• Argon is widely used for various metallurgical activities like welding magnesium, aluminium, and stainless steel. It is also used to maintain a stable atmosphere in mechanically assembled research centres.
• Radon is used in radiotherapy for the treatment of cancer.
• Xenon is widely used as a part of release tubes which serves the rapid flash necessary for photography. 
• Krypton is used for fibre lights and release tubes.

Conclusion

Group 18 elements consist of gases that are chemically unreactive and do not form compounds. These gases are helium, argon, krypton, neon, xenon, and radon. These elements have eight electrons in their outermost orbit. However, helium is the exception with two electrons. Located in the extreme right of the periodic table, they are commonly known as inert gases or noble gases due to their unreactive nature. 

All of the elements are present in a free state in the atmosphere, except radon. Some gases like helium, neon, and argon can be found as disintegrated gases in some water springs. Due to their weak Van der Waals force, these gases can be condensed at very low temperatures and are chemically latent. The noble gases have high ionisation enthalpy and high positive electron gain enthalpy.