Name: Worked example: Using formal charges to evaluate nonequivalent resonance structures | Khan Academy
Uploaded: 2020-03-27T17:35:41.000Z
Duration: 8 min 2 s
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which of the three structures contributes most

And they have given us some extra information.

and they've told us their Pauling scale electronegativity,

So pause this video and see if you can figure that out.

All right, now let's work through this together.

So there's really two things we want to optimize for

of these resonance structures contributes most

One, we want to figure out the resonance structures

where individual atoms have formal charges

We're not talking about the charge of the entire ion.

We're talking about individual atoms' formal charges,

that ideally, that would be on the most electronegative

so once again, we're not talking about the charge

All right, now with these two principles,

let's figure out which of these resonance structures

So the way that we do that is for each of these elements,

if you had just a free atom of it that was neutral,

how many valence electrons would it have?

And actually, let me make another column right over here,

You can look it up on a periodic table of elements

that carbon has four valence electrons, six total,

And the way that we calculate formal charge

how many valence electrons would say, sulfur,

a neutral, free sulfur atom typically have?

around the sulfur in this resonance structure?

And the outer electrons that we see here,

So five electrons versus six valence electrons

So you would expect a plus one formal charge here.

Another way you could think about it is typically,

so that's where we get our plus one from.

Now we can do the same exercise for the carbon here.

Carbon typically has four valence electrons