Which property distinguishes all Group 18 elements from other elements in the periodic table?

• A. They have the highest metallic character in their periods.
• B. They are highly reactive with water.
• C. They are chemically inert and rarely form compounds.
• D. They have incomplete valence electron shells.

Answer: (C)

Verified step by step guidance

1. Identify the Group 18 elements, also known as the noble gases, which include helium, neon, argon, krypton, xenon, and radon.
2. Recall that the key characteristic of noble gases is their electron configuration: they have completely filled valence electron shells, making them very stable.
3. Understand that because their valence shells are full, noble gases have little tendency to gain, lose, or share electrons, which makes them chemically inert or unreactive under normal conditions.
4. Compare this property to other groups in the periodic table, which typically have incomplete valence shells and thus tend to be more reactive to achieve stable electron configurations.
5. Conclude that the distinguishing property of Group 18 elements is their chemical inertness and rarity in forming compounds, due to their full valence electron shells.