Drawing the Lewis Structure for HNO2

Viewing Notes:

  • The HNO2 Lewis structure is easier to think of if you consider it NO2 with an H bonded to one of the oxygen atoms.
  • In HNO2 Lewis structure Nitrogen (N) is the least electronegative atom and goes in the center of the Lewis structure.
  • Check the formal charges to be sure that each atom has a formal charge of zero. In this case the formal charges will be closer to zero if you place a double bond beteween the Nitrogen atom and the Oxygen atom without the H attached.
  • In the Lewis structure for HNO2 there are a total of 18 valence electrons.

Transcript: This is the HNO2 Lewis structure: nitrous acid. When we have an H in the front of a polyatomic ion like NO2 or SO3, we know that it's going to be an acid and that the Hydrogen is going to go on the outside of one of the Oxygen. So we can put our Nitrogen in the center. We have two Oxygens. And we know that the Hydrogen will go on the outside.

Counting the valence electrons, Hydrogen has 1, Nitrogen has 5, Oxygen has 6 but we have two Oxygens, for a total of 1+5+12: 18 total valence electrons. We'll put 2 valence electrons between atoms to form chemical bonds; we've used 2, 4, 6; and then fill the octets on the outer atoms. Hydrogen has 2, so its outer shell is full. Oxygen--so, 2, 4, 6, 8, 10, 12, 14, 16, and then to the center, 18.

All of the atoms have full outer shells except for Nitrogen. It only has 6 valence electrons. We can take these two valence electrons here from the Oxygen and form a double bond and share with the Nitrogen. By doing so, the Nitrogen has a full outer shell, an octet. The Oxygen still has 8 valence electrons, it has an octet. And we're still only using 18 valence electrons that we have for the HNO2 Lewis structure. If we calculate the formal charges for the HNO2 Lewis structure, we'll find that each atom has a formal charge of 0.

So this is the Lewis structure for HNO2. This is Dr. B., thanks for watching.