Problem 25 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is an inert gas? (a) \(\mathrm{O}_{2}\) (b) argon (c) \(\mathrm{N}_{2}\) (d) \(\mathrm{H}_{2}\)

Step-by-Step Solution

Answer

Argon is an inert gas.

Step 1: Identify the Definition

Inert gases, also known as noble gases, are elements that are highly unreactive due to their filled valence electron shells. Include helium, neon, argon, krypton, xenon, and radon.

Step 2: Analyze the Options

Review each given choice to see if it matches the definition of an inert gas.- \(\mathrm{O}_{2}\) is oxygen, a reactive gas essential for combustion and respiration.- Argon is a noble gas known for its lack of reactivity.- \(\mathrm{N}_{2}\) is nitrogen, which is relatively inert but not classified as a noble gas.- \(\mathrm{H}_{2}\) is hydrogen, a reactive diatomic gas.

Step 3: Select the Inert Gas

Based on the analysis, argon is the only option that matches the criteria of an inert or noble gas.

Step 4: Conclusion

Therefore, the inert gas from the given choices is Argon.

Key Concepts

Noble Gases

Noble gases are a group of elements situated in group 18 of the periodic table. These elements are characterized by their full valence electron shells, leading to a general lack of reactivity. These gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Noble gases are often used in environments where reactions are unwanted, as they typically remain inert under standard conditions.

Noble gases have a range of applications due to their unique properties:

• Helium: Used in balloons and as a coolant in medical MRI machines.
• Neon: Known for its vivid lighting in advertising signs.
• Argon: Commonly used in welding and preserving historical documents.

Their complete valence electron shells make them stable and unlikely to form compounds easily. This stability is why they are often referred to as "inert" gases.

Valence Electron Shells

Valence electron shells are the outermost layers of electrons in an atom. These electrons play a vital role in determining the chemical properties of an element. For most elements, reactions occur in order to achieve a complete valence shell, typically comprising eight electrons, in what is known as the "octet rule".

Noble gases naturally have full valence electron shells:

• He: 2 electrons in its shell
• Other noble gases: 8 electrons in their shell

This complete shell configuration makes noble gases highly stable and largely unreactive. Other elements will often gain, lose, or share electrons to emulate this stable configuration, resulting in chemical reactions. This drive towards stability is fundamental to understanding chemical bonding and reactivity.

Argon

Argon is a well-known noble gas represented by the symbol Ar and has an atomic number of 18. It is colorless, odorless, and tasteless, distinguishing it in both its detection and applications. Argon comprises about 0.93% of Earth's atmosphere, making it the third most abundant gas after nitrogen and oxygen.

From a chemical standpoint, argon is considered inert. It doesn't form bonds readily with other elements because of its complete valence electron shell, which has 8 electrons. This full valence shell minimizes its reactivity.

• Uses of Argon: Its inertness makes it invaluable in processes requiring a non-reactive atmosphere. For example, it is used in gas chromatography to shield the samples from reacting.
• In Industry: Argon is widely used in welding to protect weld areas from oxidation.

In the scientific community, argon is handled under certain conditions to confirm its non-reactive nature and serves as an example of a true noble gas.