Questions: Noble Gases: Why Some Elements Don't React

Question 1

Why are noble gases so unreactive?

• A. They have no electrons
• B. They are too heavy to react
• C. Their outer electron levels are completely filled
• D. They exist only at very low temperatures

Answer: (C)

Noble gases have completely filled outer electron energy levels. Since they have no tendency to gain, lose, or share electrons, they have no chemical driving force to form bonds. This full arrangement is the most stable electron configuration possible.

Question 2

Helium is a noble gas even though it has only 2 outer electrons instead of 8.

• T. True
• F. False

Answer: True

Helium's first (and only) energy level can hold a maximum of 2 electrons. Since its outer level is completely filled with 2 electrons, helium has the same stability as other noble gases that have 8 outer electrons in their higher energy levels. A full outer level — regardless of whether that means 2 or 8 — is what defines noble gas stability.

Question 3

Name two practical uses of noble gases that take advantage of their unreactivity.

Model answer: Argon is used to fill incandescent light bulbs to prevent the filament from reacting with air, and helium is used to fill balloons and blimps because it is lighter than air and does not catch fire.

Noble gases are ideal for applications requiring a non-reactive environment. Argon in light bulbs prevents the hot tungsten filament from oxidizing. Helium fills balloons and airships safely because, unlike hydrogen (which is also light), helium will never ignite. Neon is used in illuminated signs. Krypton and xenon are used in certain high-performance light sources.