What is the molecular geometry of SO_3?

• A. Bent
• B. Tetrahedral
• C. Trigonal pyramidal
• D. Trigonal planar

Answer: (D)

Verified step by step guidance

1. Step 1: Determine the Lewis structure of SO_3 by counting the total valence electrons. Sulfur (S) has 6 valence electrons, and each oxygen (O) has 6 valence electrons, so total valence electrons = 6 + 3 \times 6 = 24.
2. Step 2: Draw the skeletal structure with sulfur as the central atom bonded to three oxygen atoms. Distribute the electrons to satisfy the octet rule for each atom, considering resonance structures if necessary.
3. Step 3: Count the regions of electron density (bonding and lone pairs) around the central sulfur atom. In SO_3, sulfur forms three double bonds with oxygen atoms and has no lone pairs on the central atom.
4. Step 4: Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. Three regions of electron density with no lone pairs around the central atom correspond to a trigonal planar geometry.
5. Step 5: Confirm that the bond angles are approximately 120° in a trigonal planar structure, consistent with the arrangement of the three oxygen atoms around sulfur in SO_3.