Which statement correctly describes the chemical behaviour of inert gases (noble gases)?

Introduction / Context:
This question tests your understanding of the basic properties of inert gases, also known as noble gases, such as helium, neon, argon, krypton, xenon and radon. These gases occupy group 18 of the periodic table and are known for their very low chemical reactivity. Recognising this property is fundamental in both general chemistry and periodic table questions.

Given Data / Assumptions:

• We are asked about the chemical behaviour of inert gases.
• Options include statements about miscibility with water, stability, reactivity and reducing ability.
• We assume standard school level understanding that noble gases have complete valence shells.

Concept / Approach:
Inert gases have a completely filled valence shell of electrons. This stable electronic configuration makes them extremely reluctant to gain, lose or share electrons, so they do not normally form chemical compounds. As a result, they are described as chemically unreactive or inert. While some heavier noble gases can form a few compounds under extreme conditions, at school level they are treated as unreactive. Therefore, the statement that they are chemically unreactive is the best description.

Step-by-Step Solution:
Step 1: Recall the group of inert gases: helium, neon, argon, krypton, xenon and radon. Step 2: Each noble gas has a full valence shell, such as 2 for helium and 8 for neon and argon. Step 3: Because their valence shell is full, there is no strong tendency to gain or lose electrons. Step 4: This electronic stability makes them very unreactive under normal conditions. Step 5: Therefore, the phrase chemically unreactive is the correct description of their behaviour.

Verification / Alternative check:
You can verify this by recalling that noble gases were long thought to be completely inert and were called inert gases in older textbooks. They do not normally form compounds with other elements and are used in applications where a non reactive atmosphere is required, such as in lighting, welding and preserving reactive materials. Only advanced courses discuss rare compounds of xenon and krypton, but these do not change the general statement that noble gases are chemically unreactive compared to other elements.

Why Other Options Are Wrong:
The phrase miscible with water refers to physical mixing, not chemical reactivity, and noble gases are only slightly soluble in water. Saying they are not stable is incorrect because their filled valence shells make them very stable. Chemically very active is the opposite of their actual behaviour. Strong reducing agents are substances that readily donate electrons, while noble gases do not easily donate or accept electrons, so this description is also wrong.

Common Pitfalls:
Students sometimes equate inert with physically inactive in every sense, forgetting that noble gases can dissolve slightly in fluids or move freely as gases. However, the term inert in this context relates specifically to chemical reactivity. Another pitfall is to overemphasise exceptional xenon compounds and think that inert gases are generally reactive, which is not true within the scope of school level chemistry.

Final Answer:
Inert gases are best described as chemically unreactive under normal conditions.