Question

Which of the following is an inert gas.
A. \[{{\rm{H}}_2}\]
B. \[{{\rm{O}}_2}\]
C. \[{{\rm{N}}_2}\]
D. Argon

Answer 1

Hint: The elements present in the periodic table which have no ability to gain or lose electrons from their valence shell are said to be chemically Inert. They have a complete valence shell. These elements are in gaseous forms therefore called as inert gases.

Complete Step by Step Answer:
In the periodic table there are a total of 18 groups and 7 periods in which various elements are arranged according to their increasing atomic numbers. The elements with the same valence shell electronic configuration are present in the same group and exhibit similar properties.

In group 18 of periodic table, the general valence shell electronic configuration of element is \[{\rm{n}}{{\rm{s}}^2}{\rm{n}}{{\rm{p}}^6}\]. The outer valence shell of group 18 elements is complete. Due to their complete valence shell these elements have no ability to gain or lose electrons. These elements are chemically unreactive. They have no ability to form many compounds. Group 18 elements are gases and chemically inert in nature. Therefore, they are called inert gases.

Various elements present in Group 18 are as follows: 1) Helium (He), 2) Neon (Ne), 3) Argon (Ar), 4) Krypton (Kr), 5) Xenon (Xe) and 6) Radon (Rn). All of these have complete valence shells and are inert gases.

Inert gases have high ionisation enthalpy due to the energy required to remove electrons from the valence shell is very high. Also, the group 18 elements have zero affinity to gain new electrons in its valence shell. Due to their complete valence shell, Group 18 is also called Zero group elements or noble gases.
So, option D is correct

Additional Information: The group 18 elements have small atomic radii which increases down the group due to the addition of new shells. Due to increase in size along the group, the ionisation enthalpy increases down the group.

Note: \[{{\rm{H}}_2}\], \[{{\rm{N}}_2}\] and \[{{\rm{O}}_2}\] are also gases but belongs to group 1, 15 and 16. Their outer electronic configuration is incomplete and not inert in nature. These have the ability to interact with other elements.