Iodine oxidises Sulphur from +2 in [S2O4]-2 to?? In [S4O6]-2

I work this out to be 2.5 but how can this be? Oxidation numbers surely have to be integers!

Fankyouverymuch! :D

The Sulfur is actually in 2 different Oxidation states in the same molecule. Look at the structure and this becomes more obvious. http://upload.wikimedia.org/wikipedia/commons/c/c8/Tetrathionate-ion-2D.png

2.5 is correct

This thread is 2 years old. Thank you for looking at the post date before answering. Thanks.