Sulfur dioxide, SO₂, is an atmospheric pollutant produced by the combustion of sulfur-containing fuels. Two nonequivalent Lewis diagrams that satisfy the overall stoichiometry are described below.
• Structure A: One oxygen atom (labeled O₁) is double-bonded to the sulfur atom, and the second oxygen atom (O₂) is single-bonded to sulfur. All lone pairs needed to complete octets are added.
• Structure B: Both oxygen atoms are double-bonded to sulfur with all lone pairs needed to complete octets.
Answer the following questions about these candidate representations of SO₂.
(a) For each atom in Structure A, calculate the formal charge. Organize your work in a clearly labeled table.
(b) Repeat the formal-charge calculations for all atoms in Structure B.
(c) Evaluate the extent to which each atom in Structures A and B satisfies the octet rule. Explicitly identify any atoms that exceed or fall short of an octet.
(d) Which structure makes the greater contribution to the actual electronic structure of SO₂? Justify your answer by comparing the results of parts (a)–(c) and commenting on electronegativity considerations.
(e) Experimental measurements show that the two S–O bond lengths in gaseous SO₂ are identical and intermediate between typical S–O single- and double-bond lengths. Explain how your answer to part (d) accounts for this observation.