# Formal Charge on Sulfate

#### ManzRDH

##### Dinene RDH, BA
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Sulfate (SO4)-2

Can someone exlain the formal charge on oxygen?

I found sulfur's formal charge to be 2 which is correct

Formal Charge= V -1/2 N bonding- N non-bonding

#### vertical bite

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ManzRDH said:
Sulfate (SO4)-2

Can someone exlain the formal charge on oxygen?

I found sulfur's formal charge to be 2 which is correct

Formal Charge= V -1/2 N bonding- N non-bonding

Wow you are having a hard time huh? What exactly are you studying with?

O is always -2

there are 4 Oxygens. 4 x -2 = -8

the sum of the oxidation numbers must = -2

so Sulfur must be 6 !

-8 + 6 = -2

get it?

#### drat

##### I catch huge fish.
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ManzRDH said:
Sulfate (SO4)-2

Can someone exlain the formal charge on oxygen?

I found sulfur's formal charge to be 2 which is correct

Formal Charge= V -1/2 N bonding- N non-bonding
First, congrats on knowing the difference between formal charge and oxidation number, unlike vertical bite.

It's easiest if you draw the Lewis dot structure for sulfate...I can't do it on the computer here...

But, you're right, the equation to calculate the formal charge is:
# of valence electrons - # of non bonding electrons - (1/2)*# of bonding electrons.

Look at the Lewis dot structure. . .
For the S, you have 6 valence electrons, 0 nonbonding electrons, and 8 bonding electrons....plug these values into the question and you get 2, like you said.

6 - 0 - (1/2)*8 = 2

For O, you have 6 valence electrons, 6 nonbonding electrons, and 2 bonding electrons....plug these values into the question and you get -1

6 - 6 - (1/2)*2 = -1

#### vertical bite

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OH I got burned !!!

Finally someone in these forums with brains.

Ugly dog but brains.......

#### luder98

##### Senior Member
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drat said:
First, congrats on knowing the difference between formal charge and oxidation number, unlike vertical bite.
And oxygen's oxidation number is not always -2.

#### vertical bite

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Good god who cares ????

Ok I think its gonna be darn rare to see a peroxide question.

MAn.............................

#### drat

##### I catch huge fish.
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luder98 said:
And oxygen's oxidation number is not always -2.
'Tis true. Peroxides are the exception where O is -1. But it wasn't me who said O is always -2!! Don't go mixing me and Vert up. I'm utterly offended.

But, let's not talk about oxidation 'cause the OP had a question about formal charge...No need for confusion -- but it's important to recognize there IS a difference!

#### vertical bite

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Peroxides?

I posted that above you.

I swear its hard being so smart.

I am in dental school. are you ?

#### vertical bite

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drat said:
'Tis true. Peroxides are the exception where O is -1. But it wasn't me who said O is always -2!! Don't go mixing me and Vert up. I'm utterly offended.

But, let's not talk about oxidation 'cause the OP had a question about formal charge...No need for confusion -- but it's important to recognize there IS a difference!

Id bet \$100 that you have to look that up..........

#### drat

##### I catch huge fish.
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vertical bite said:
Id bet \$100 that you have to look that up..........
okay. i win. i'm awesome. go me.

i'm a chemist so if i didn't know the answer to that question, i'd be pretty pathetic. but i'm willing to entertain other chemistry questions if you'd like to try and stump me.

#### vertical bite

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drat said:
okay. i win. i'm awesome. go me.

i'm a chemist so if i didn't know the answer to that question, i'd be pretty pathetic. but i'm willing to entertain other chemistry questions if you'd like to try and stump me.

Well good stuff then.

I rem. it too but have never seen it EVER come up so sue me.

#### luder98

##### Senior Member
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drat said:
'Tis true. Peroxides are the exception where O is -1. But it wasn't me who said O is always -2!! Don't go mixing me and Vert up. I'm utterly offended.

But, let's not talk about oxidation 'cause the OP had a question about formal charge...No need for confusion -- but it's important to recognize there IS a difference!
Of course I knew that it wasn't you. I only wanted to add to your comment. BTW, it can also be +1 when it's in a compound with a more electronegative element like F. I do not want to outsmart anyone here because I know I'm just an average Joe and there are plenty of people (you are one of those) on this forum who are definitely smarter/better than me. I'm sure you know my intention.

#### drat

##### I catch huge fish.
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luder98 said:
Of course I knew that it wasn't you. I only wanted to add to your comment. BTW, it can also be +1 when it's in a compound with a more electronegative element like F. I do not want to outsmart anyone here because I know I'm just an average Joe and there are plenty of people (you are one of those) on this forum who are definitely smarter/better than me. I'm sure you know my intention.
Ah yes, I suppose that is the case for OF2 and such. Good stuff, luder98. Hadn't really thought of that!! I love chemistry!

But for future DAT takers, don't worry about such a rare occurance!