Which group contains the noble gases?

• A. Group 18
• B. Group 2
• C. Group 7
• D. Group 3

Answer: (A)

The key idea is where the noble gases sit on the periodic table and what that means for their behavior. Noble gases occupy the far-right column of the main sections of the table. That placement reflects their full valence electron shells, which makes them unusually stable and largely unreactive. Helium has a full shell with 2 electrons, while the others have 8 in their outer shell, leading to their characteristic inertness. That combination of being in the far-right column and having complete outer shells is why this group is associated with the noble gases. The other groups listed differ in how many valence electrons they have and how reactive they are (alkaline earth metals with two valence electrons, halogens with seven and very reactive, transition metals with variable valence), so they don’t contain the noble gases.