Noble gases are unreactive because, except for helium, they have a stable arrangement of:

• A. seven electrons in their outermost shell
• B. ten electrons in their outermost shell
• C. eight electrons in their outermost shell
• D. two electrons in their outermost shell

Answer: (C)

Verified step by step guidance

1. Understand that noble gases are elements in Group 18 of the periodic table, known for their chemical inertness or lack of reactivity.
2. Recall the concept of the octet rule, which states that atoms tend to be most stable when they have eight electrons in their outermost (valence) shell, except for the first shell which is stable with two electrons.
3. Recognize that helium is an exception because it has only one electron shell, which is stable with two electrons, not eight.
4. For all other noble gases (like neon, argon, krypton, xenon, and radon), their outermost shell contains eight electrons, making them chemically stable and unreactive.
5. Therefore, the correct stable electron arrangement for noble gases (except helium) is eight electrons in their outermost shell.