Question

Which of the following does not obey the octet rule?

• A. \( SF_6 \)
• B. \( H_2O \)
• C. \( CO_2 \)
• D. \( CH_4 \)

Hint:

Elements in Period 3 or higher can exceed the octet rule by utilizing their d-orbitals.

Answer 1

The Correct Option is A

The octet rule states that atoms tend to gain, lose, or share electrons to have a full valence shell (8 electrons). 

In \( SF_6 \), sulfur forms six bonds, expanding its valence shell to 12 electrons: \[ \text{Valence electrons of S} = 6 + 6(1) = 12. \] 

Explanation: \( H_2O \), \( CO_2 \), and \( CH_4 \) all obey the octet rule. \( SF_6 \) does not obey the octet rule due to its expanded valence shell.