Which of the following is the correct Lewis dot structure for sulfur trioxide (SO_3), a neutral compound?

• A. Sulfur atom in the center with three single bonds to three oxygen atoms; each oxygen has three lone pairs.
• B. Sulfur atom in the center with one double bond and two single bonds to oxygen atoms; each oxygen has two lone pairs.
• C. Sulfur atom in the center with three triple bonds to three oxygen atoms; each oxygen has one lone pair.
• D. Sulfur atom in the center with three double bonds to three oxygen atoms; each oxygen has two lone pairs.

Answer: (D)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons available for the molecule. Sulfur (S) has 6 valence electrons, and each oxygen (O) atom has 6 valence electrons. Since there are three oxygen atoms, total valence electrons = 6 (S) + 3 × 6 (O) = 24 electrons.
2. Step 2: Arrange the atoms with sulfur in the center and three oxygen atoms surrounding it. Connect each oxygen atom to sulfur with a single bond initially. Each single bond represents 2 electrons, so 3 single bonds use 6 electrons.
3. Step 3: Distribute the remaining electrons to satisfy the octet rule for the oxygen atoms first. Each oxygen needs 8 electrons total (including bonding electrons). After placing lone pairs on oxygens, check if sulfur has a complete octet. If sulfur lacks an octet, consider forming double bonds by sharing lone pairs from oxygen atoms with sulfur.
4. Step 4: Evaluate resonance structures and formal charges. The most stable Lewis structure minimizes formal charges and satisfies the octet rule for all atoms. For SO_3, the best structure has sulfur forming three double bonds with oxygen atoms, each oxygen having two lone pairs, and sulfur having an expanded octet.
5. Step 5: Confirm that the final Lewis structure is neutral overall, with no formal charges or minimized formal charges, and that it matches the description: sulfur in the center with three double bonds to oxygen atoms, each oxygen having two lone pairs.