Which of the following best explains why noble gases are chemically stable according to the octet rule?

• A. They have a complete valence shell with eight electrons.
• B. They easily gain or lose electrons to form ions.
• C. They have unpaired electrons in their outer shell.
• D. They have partially filled d orbitals.

Answer: (A)

Verified step by step guidance

1. Understand the octet rule: atoms tend to be most stable when they have eight electrons in their valence (outermost) shell, resembling the electron configuration of noble gases.
2. Recall that noble gases naturally have a full valence shell, meaning their outermost energy level is completely filled with electrons, typically eight (except helium, which has two but is still stable).
3. Recognize that because their valence shells are full, noble gases have little tendency to gain, lose, or share electrons, making them chemically inert or stable.
4. Evaluate the given options: the correct explanation must relate to the full valence shell and the resulting stability, not to gaining/losing electrons, unpaired electrons, or partially filled d orbitals.
5. Conclude that the best explanation is that noble gases are chemically stable because they have a complete valence shell with eight electrons, satisfying the octet rule.