What is the name of #S_2O_3#?

1 Answer
May 1, 2016

Answer:

#S_2O_3^(2-)# is the #"thiosulfate anion"#. Note that this has a formal, double negative charge.

Explanation:

In a thiosulfate group one sulfur atom has formally replaced one of the oxygen atoms of sulfate dianion, #SO_4^(2-)#.

In sulfate, the oxidation number of #S=+VI#. We could imagine that in thiosulfate, the central #S# also has this oxidation state, and the terminal sulfur has an oxidation state of #-II#, i.e. the same oxidation state as the oxygen atoms, which are in the same Group as sulfur. The average #(6-2)/2=+II# is the same as we would get if we assumed the sulfurs were in equivalent oxidation states.