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QuestionChemistry

Which of the following is an exception to the octet rule? Ignore that hydrogen has a duet. A. CO^2 B. NH^4 + C. H^2O D. SF^6
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Step 1:
I'll solve this step by step, focusing on the electronic structure and valence electrons for each molecule.

Step 2:
: Understanding the Octet Rule

The octet rule states that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration of 8 valence electrons (like noble gases).

Step 3:
: Analyze Carbon Dioxide (CO2)

- Total valence electrons: $$4 + (2 \times 6) = 16
- Carbon has 4 valence electrons - Each oxygen has 6 valence electrons - In CO^2, carbon forms double bonds with oxygens - Carbon and both oxygens achieve 8 electrons - Follows the octet rule

Step 4:
: Analyze Ammonium Ion (NH^4 +)

- Nitrogen has 5 valence electrons - Hydrogens each have 1 valence electron - In NH^4 +, nitrogen forms single bonds with 4 hydrogens - Loses one electron to become a positive ion - All atoms achieve 8 electrons - Follows the octet rule

Step 5:
: Analyze Water (H^2O)

- Oxygen has 6 valence electrons - Hydrogens each have 1 valence electron - Oxygen forms single bonds with hydrogens - All atoms achieve their electron configuration - Follows the octet rule

Step 6:
: Analyze Sulfur Hexafluoride (SF6)

- Total valence electrons: $$6 + (6 \times 7) = 48
- Sulfur has 6 valence electrons - Fluorine has 7 valence electrons - In SF^6, sulfur forms single bonds with 6 fluorines - Sulfur expands its octet to 12 electrons - EXCEPTION to the octet rule

Final Answer

SF^6 is the exception to the octet rule because sulfur expands its valence shell beyond 8 electrons.