The key to understanding and being prooficient at chemical reactions is knowing your ox-states and valences.

However I'm halfway there. There are something I need to work on.

When trying to determine the ox-state of a compound that contains oxygen, for example PO4, how would you find the ox-state? Each O has a valence of -2, there are 4 of them so oxygen amounts to -8. But what would the valence of phosphorus (P) be? What would be the final ox-state?

In short, HOW DO YOU DO THIS CRAP?

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If you consult the periodic table, you will note that Phosphorus has 5 valence electrons

Oxygen as you may know is more electronegative than phosphorus and will therefore pull the electrons from the Phospohorus atom

In this polyatomic ion, you should recall that it has a charge of 3-

You are correct that total charge on the oxygen atoms is 8-

Since Phosphorus loses 5 electrons it has a charge of 5+

Do the math

Minus 8 and positive 5 work out to minus 3

Ah I see. Electronegavity.

With Flouring being the most electronegative atom, PF4, would have an oxstate of +1?

-4 + 5 = 1
Flourine total phosphorus total

Fluorine drags electrons towards itself no?

If this is totally wrong, I give you permission to spank my bottom.

OK

Well, I worded that the way I did hoping that it would make a bit more sense in terms of counting.

In actuality here is what is happening...

In these cases we are talking about covalent bonding so there is not any transfer of electrons although often times we talk about it as if there were.

In the case of the phosphate ion, three of the oxygens pair up with one of the electrons and the fourth one covalently bonds with two of them leaving three unpaired electrons.

Three electrons are then picked up from elsewhere creating the 3- charge.

When determining oxidation states, however, we often don't think of it in this way. Instead we look at the overall charge of the unit in question and dole out charges that we know first such as oxygen and the 2-. Since we get minus 8 from that, Phosphorus must be 5+ so that the overall charge can be 3-. Remember though that there really is no transfer of electrons here.


In the case of PF4 there is one unpaired electron on the phosphorus which would most likely be lost to give a plus one charge.

No you explained it well, otherwise I wouldn't have guessed what PF4 would be would I? Thanks dude.