Counting σ Bonds in Molecular Structures

Steps:

• Examine the diagram to identify all atoms and their bonding types (single, double, triple).
• Count each single bond as 1 σ bond; each double bond as 1 σ bond (plus 1 π); each triple bond as 1 σ bond (plus 2 π).
• Include σ bonds from C-H, O-H, or other terminal bonds.
• Total the σ bonds across the entire molecule.

Why C is correct:

• The structure features 18 σ bonds, matching the rule that every bonded atom pair has exactly one σ bond from end-to-end orbital overlap.

Why the others are wrong:

• A: Undercounts by ignoring σ components in multiple bonds.
• B: Misses a few single or multiple bond σ contributions.
• D: Overcounts by treating π bonds as additional σ bonds.

Final answer: C