Can someone please double check if I have oxidised the number of sulfur correctly for the following ions? The question is in the description box below.

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My answers are #S_20^2-(_4) and s=4+
and the other one s=3

1 Answer
Jan 24, 2018

Your sulfur-based polyatomic anions are:

"S"_2"O"_4^(2-)

"S"_2"O"_3^(2-)

Dithionite has four oxygens, each of the typical oxidation state of -2 (as this is not a peroxide), so by conservation of charge...

overbrace(2xxO_S)^(S_2) + overbrace(4 xx -2)^(O_4) = overbrace(-2)^"charge"

and each sulfur has on average, color(blue)(O_S = +3).

Thiosulfate has three oxygens, each of the typical oxidation state of -2 (as this is not a peroxide), so by conservation of charge...

overbrace(2xxO_S)^(S_2) + overbrace(3 xx -2)^(O_3) = overbrace(-2)^"charge"

and each sulfur has on average, color(blue)(O_S = +2).


In reality this is not true; the second one is a sulfate analog, so we distinguish between the central sulfur and the outer sulfur...

  • "S"_2"O"_3^(2-) then has a central sulfur oxidation state of +4 and outer sulfur oxidation state of -2 (just like each oxygen atom).