[jsmith613]

http://en.wikipedia.org/wiki/File:Sulfate-ion-2D-dimensions.png

Why are two of the oxygens negativley charged and the other two not?

[sjb]

http://en.wikipedia.org/wiki/File:Sulfate-ion-2D-dimensions.png

Why are two of the oxygens negativley charged and the other two not?

Have you seen the parent article at http://en.wikipedia.org/w/index.php?title=Sulfate&oldid=391173215 - does that help?

[jsmith613]

http://en.wikipedia.org/w/index.php?title=Sulfate&oldid=391173215[/url] - does that help?

If i justify with oxidation states, oxygen has 2- and if we add an electron it should go down to 3-, so I can't work out why it happens

please help

[vmelkon]

Sulfur makes a covalent bond with oxygen and sulfur can make up to 6 bonds. That is the case for SO3 (sulfur trioxide).
In SO4, which has a -2 charge, the -2 charge can't exist on a single oxygen. If it did, then SO4(-2) would break down to SO3 and O(-2).
The charge is spread over 2 oxygen atoms.

I'm sure an even deeper explanation is possible by looking at the orbitals.

[jsmith613]

Sulfur makes a covalent bond with oxygen and sulfur can make up to 6 bonds. That is the case for SO3 (sulfur trioxide).
In SO4, which has a -2 charge, the -2 charge can't exist on a single oxygen. If it did, then SO4(-2) would break down to SO3 and O(-2).
The charge is spread over 2 oxygen atoms.

I'm sure an even deeper explanation is possible by looking at the orbitals.

Perhaps my question was not clear enough. If SO4 can have up to six bonds, surley it should not matter the molecule it should always have six bonds. Therefore why has oxygen 'decided to be negative'

[sjb]

If i justify with oxidation states, oxygen has 2- and if we add an electron it should go down to 3-, so I can't work out why it happens

please help

What do you make the oxidation states of the sulfur and the other two oxygens, then?

[jsmith613]

If i justify with oxidation states, oxygen has 2- and if we add an electron it should go down to 3-, so I can't work out why it happens

please help

What do you make the oxidation states of the sulfur and the other two oxygens, then?

Oxygen is 2- and sulphur is 6+.
Oh I see were this is going. I was apparently wrong !

sorry!

thanks for the help