Chemical Bonding: HClO₃ Lewis Structure

Drawing the Lewis Structure for HClO₃

Viewing Notes:

• In the HClO₃ Lewis structure Chlorine is least electron electronegative atom and goes in the center of the Lewis structure. Remember, Hydrogen always goes on the outside.
• 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 HClO₃.
• For the Lewis structure for HClO₃ you should take formal charges into account to find the best Lewis structure for the molecule.
• In the Lewis structure for HClO₃ there are a total of 26 valence electrons.

Transcript: This is the HClO3 Lewis structure. In order to do this Lewis structure, you need to recognize that it's an acid. There's an H in front of a polyatomic ion. So when we look at that, we know that the H is going to be attached to the outside of one of these Oxygens when we draw the structure. We'll put the Chlorine at the center--it's the least electronegative. We have 3 Oxygens, we'll put them around the outside; and we'll put that H on the outside of one of the Oxygens.

For HClO3 we have a total of 26 valence electrons. We'll put 2 between the atoms to form the chemical bonds. Then we'll go around the outside of the Oxygens to fill the octets. So we've used 2, 4, 6, 8, 10, and 24. We have 2 more, so we'll put them on the Chlorine, complete the octet for Chlorine. So we've used all 26 valence electrons. All of the Oxygens and Chlorines have 8 valence electrons, their outer shells are full. And the Hydrogen has 2 valence electrons, its outer shell is full.

So this looks like a good structure for HClO3. The thing that you want to look at, though, is Chlorine is in period 3 of the periodic table. It can hold more than 8 valence electrons. So we really should check our formal charges to see if this is the best structure for HClO3. When we calculate the formal charges, we find that the Chlorine has a +2 charge, while these Oxygens out here have a -1 charge, each of them. Everything else is 0, though. Since we want our formal charges to be as close to 0 as possible, we're going to need to do something to minimize the charges.

What we can do is move a pair of electrons from the outside of the Oxygen to the middle to form a double bond. When we do that, the formal charge on the Oxygen here becomes 0 and the Chlorine now has a +1 charge. So let's do that again with this other Oxygen. By doing that, we now have a formal charge of 0 on all of the atoms in the molecule. So we've used all the valence electrons for the HClO3 Lewis structure. We have octets satisfied on the Oxygens and Hydrogens. The Chlorine has more than 8, but that's OK, it's in period 3, and our formal charges are 0 for all of the atoms on the molecule.

That makes this the best Lewis structure for HClO3. This is Dr. B., and thanks for watching.