Drawing the Lewis Structure for H2SO4

Viewing Notes:

• In the H2SO4 Lewis structure Sulfur is least electron electronegative atom and goes in the center of the Lewis structure.
• When we have an H (or H2) in front of a polyatomic molecule (like CO3, SO4, NO2, etc.) we know that it's an acid. This means that the Hydrogen atoms will be attached to the outside of the oxygen molecules. Knowing this information makes it much easier to draw the Lewis structure for H2SO4.
• For the Lewis structure for H2SO4 you should take formal charges into account to find the best Lewis structure for the molecule.
• In the Lewis structure for H2SO4 there are a total of 32 valence electrons.

Transcript: This is the H2SO4 Lewis structure: sulfuric acid. The key to understanding this Lewis structure is that you have these H's in front, and then you have this polyatomic ion. That means you're going to have an acid and that these H's are going to be attached to the outside of the Oxygens. So we'll put the Sulfur in the center; it's the least electronegative. We have 4 Oxygens. And then the Hydrogens, as we said, they'll go on the outside of the Oxygens. We have 2 Hydrogens.

For H2SO4 we have a total of 32 valence electrons. Put a pair between the atoms. We're forming chemical bonds here. We've used 8, 10, 12, and then around the outside to fill the octets on the Oxygens, 14, and 32. So this looks like a pretty good Lewis structure for H2SO4. We've used all 32 valence electrons and each of the atoms has a full outer shell. We should check the formal charges, though. Sulfur is in period 3 on the periodic table, and it can hold more than 8 valence electrons. It's a good idea just to see how the formal charges pan out.

Turns out that Sulfur has a +2 formal charge and each of these Oxygens here has a -1. We'd like our formal charges to be as close to 0 as possible. So what we can do is form double bonds with the Oxygens--the Oxygens that don't have a Hydrogen on them-- and see how that works out with the formal charges. So let's take these electrons here to form a double bond with Sulfur, and we'll do the same thing over here. Since we had a +2, we're going to need to move both of those in there to get rid of that.

When we form those two double bonds and recalculate our formal charges, we'll find that the formal charge on each atom in the H2SO4 Lewis structure is now 0. That makes this a much better structure for the sufuric acid molecule. So when you see something like Sulfur there, make sure you check the formal charges.

I'm Dr. B., and thanks for watching.

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