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How many resonance structures are there for S2O2 and S2O3?

1 Answer
Feb 5, 2017

Answer:

Do you mean #"SO"_4^(2-)#, #"sulfate ion"#, and #"S"_2"O"_3^(2-)#, #"thiosulfate ions"#?

Explanation:

Sulfate dianion is a very common counterion. Here we have sulfur in a #VI+# oxidation state. For #"thiosulfate ion"#, ONE of the oxygens has been replaced by a sulfur. And in the replacement, sulfur has assumed PRECISELY the same oxidation state (#-II#) of the oxygen it replaces (and such a formalism is reasonable, because sulfur and oxygen are in the same group!). The average oxidation of both sulfurs is still #+II#, but we can individually assign separate oxidation states to the central and terminal sulfurs.

Both sulfate and thiosulfate ions have resonance structures, typically #""^(-)O-S(=O)_2-O^-#, and #""^(-)O-S(=O)_2-S^-#. Of course, the negative charges are delocalized around the chalcogen atoms.