[cliverlong]

Hi,

   I am not understanding why Sulphate has a charge of 2- 

   I am thinking in terms of electrons from the sulphur and oxygen atoms and the bonds they form.

   I have read that at a simple level the six outer electrons of sulphur form six bond pairs with oxygen. There are two covalent double bonds between sulphur and two oxygens. There are two further single bonds between sulphur and the other two oxygens. I am not understanding what those single bonds are.

   On top of that I am reading that the bond electrons are delocalised - so that the bonds between sulphur and oxygen are actually identical and this leads to a tetrahedral shape for the sulphate ion  - and there are electrons "over" which make the ion charged.

I am not grasping what that means in terms of

the source of those electrons in bonds and delocalised (i.e. which electrons from sulphur, which from oxygen)
the position of the electrons on the ion i.e. which electrons are in bonds are which are delocalised
how that arrangement of electrons affects the charge on the ion i.e. leads to the 2- charge

  If anyone can explain I will much appreciate.


Thanks

Clive

[ARGOS++]

Dear Cliverlong;

Did you got your information from:   "Sulfate” ?
Sulfate is the Salt of “Sulfuric Acid”.
Compare it with the “Sulfuric Acid”, you will find also on ‘Wiki’, and get so most of your answers.
(Simply spoken: “After the Acid has given away it will be hard ‘to disdinguish’ between two sorts of Oxygens”.)

I hope it may be already of help to you.

Good Luck!
                    ARGOS⁺⁺

[merkl]

http://en.wikipedia.org/wiki/Sulfate

I wiki'd it, and it does have a section on its bonding and structure. Hopefully thats some help.

[cliverlong]

http://en.wikipedia.org/wiki/Sulfate

I wiki'd it, and it does have a section on its bonding and structure. Hopefully thats some help.

I did read that wiki entry and section but I couldn't understand it.

I guess I'm a bit stumped.

Edit: Re-reading the entry, is "Formal Charge" the key concept?



Thanks,

Clive

[ARGOS++]

Dear Cliverlong;

I hope that you at least extracted from my “Sulfate” (it’s the same Link!) and from “Sulfuric Acid”, where the Charge of -2 is coming.
Otherwise you have first to understand what an acid is!

Let’s try the other a little simplified:
How will you be able to distinguish the two Kind(s) of Oxygen if in the “next moment” two other Oxygens may hold these negative Charges?
But why should the “Sulfate Ion” do such?
It does it even more effective: It uses all the “localised thought” States together at the same time, or how Chemists talk about: -
Both negative Charges are “de-localised”, and that gives the Ion the possibility to lower quite significantly  its “Inner Energy”, what means: It’s very much more stabile!

I hope it helps to make “all” a little more clearly.

Good Luck!
                    ARGOS⁺⁺

[cliverlong]

Dear Cliverlong;

I hope that you at least extracted from my “Sulfate” (it’s the same Link!) and from “Sulfuric Acid”, where the Charge of -2 is coming.
Otherwise you have first to understand what an acid is!

Sorry, I don't get the relevance of acid to this.

Yes, H₂SO₄(aq) contains two H⁺ ions so you can deduce SO₄ charge is 2-

But it isn't the presence of the hydrogen ion making the charge on the sulphate - the sulphate is just charge 2- and it is that that attracts the hydrogen ion - not the other way round. Or am I still missing your point?

As a different example, look at the neutral salts sodium sulphate and copper (II) sulphate. In those cases sulphate still has charge 2- and no hydrogen ion present, no acids.   

Let’s try the other a little simplified:
How will you be able to distinguish the two Kind(s) of Oxygen if in the “next moment” two other Oxygens may hold these negative Charges?

But where is this negative charge coming from in terms of the electrons from the original atoms?

Thanks

Clive

[ARGOS++]

Dear Cliverlong;

You are absolutely right! – that “it isn’t the presence of the Hydrogen Ion making the Charge …”!

But what’s the consequence of that?: 
Do you believe there is another “Sulfate Ion” present in “Sulfuric Acid”, then in its Salt – the  “Sulfate”?

If you add e.g. Na-OH to H2SO4 you are building Water that’s going out of the ionic form, but all the Na⁺ and the SO₄^2- remains in exactly the same Kind/Form, as at the Begin.
They are only a little more diluted.

First you may read about “Ionic Bonds” on:   "Ionic Bond ”.
Please read also in your textbook about:  Salt, Acid, Base, and Dissociation.
I think then most is coming more clear.


Good Luck!
                    ARGOS⁺⁺

[cliverlong]

Section 3 and 4 of this ...

http://www.madsci.org/posts/archives/2000-01/949098457.Ch.r.html

seems to address the issue. It all seems a bit deep to me - but may repay some study. 


Clive

[ARGOS++]

Dear Cliverlong;

If you really like do it in such a puristic way for a Beginners?,     –  Ok, it’s your decision.

But I never believe that it will be a good way to first try to climb such puristic Heavens, before you have enough knowledge about the “much more simpler” things, that will be required for.

And you have to think about, as it is told in your reference:

These are all only more or less adequate Models for the Reality!

Anyway: I wish you all the best for your hard way!

Good Luck!
                    ARGOS⁺⁺