Why is Sulphate 2-?

Valmont

I really hope somebody can explain this to me because I just cannot seem to grasp the oxidation states of compounds.

I know that SO4 has a charge of 2- but I can't see how.

Each oxygen atom has a charge of 2- and if I multiply that by 4 I have 8-. Now to balance that with Sulphur to reach an overall charge of 2- I need to have the sulphur atom 6+ only my chemistry book tells me an atom cannot gain or lose more than 3 electrons.

So how does SO4 have a charge of 2-? I'm starting to fall behind on my chemistry mooc spending so much time on this problem.

sammyjo90

god I havnt done Leaving cert chemistry for 6 years but Sulphur can have oxidation states from -2(rare) all the way up to +6 so your answer is correct.

Don't get bogged down on electron loss etc oxidation state is really the charge the atom WOULD have if all bonds were ionic. its not the actual charge

Valmont

sammyjo90 wrote: »

oxidation state is really the charge the atom WOULD have if all bonds were ionic. its not the actual charge

SO is covalent, right? And you're telling me that the charge only relates to an ionic compound? Either way I've moved on and it hasn't tripped me up just yet. Thanks.

sammyjo90

Its what the charge WOULD be if the compound WERE ionic. Its not for ionic compounds only

SOL

What chemistry book says an atom can only lose 3 electrons? - I suspect this may refer to a specific case

Also, Sammyjo is right in that the oxidation numbers only represent a way of counting the electrons and where they are rather than actual charges...