Chemical Bonding: N₂O Lewis Structure

Drawing the Lewis Structure for N₂O

Viewing Notes:

• The Lewis structure for N₂O has three possible structures that all fill the octets of each atom.
• Remember that the most electronegative atom goes in the center of the structure. Nitrogen is the least electronegative in this molecule.
• You'll want to calculate the formal charges on each atom to make sure you have the best Lewis structure for N₂O. N₂O is a good example of why formal charges are useful in chemistry.
• For the N₂O Lewis structure you'll want to select the structure with formal charges closed to zero. In this case there are two similar structures. Choose the structure in which the most electronegative atom (in the case of this structure the Oxygen atom) has the negative formal charge.
• There are 16 valence electrons in N₂O.

Transcript: Let's do the N2O Lewis structure. N2O has 16 total valence electrons. There's three ways we can draw it, and all of them work pretty well. Let's take a look. For each structure, the atoms have fulfilled their octets, and for each Lewis structure, all the 16 valence electrons have been used. So we need to decide which one of these is going to be the best structure. To do so, we're going to have to look at formal charges.

Let's start with this one right here. For this first Nitrogen right here, on the periodic table Nitrogen has 5 valence electrons; nonbonding, these, 4; and then bonding, we have two bonds here so that's 4 valence electrons. We divide by 2. So the total formal charge for this Nitrogen right here, it's going to be negative 1. For the Nitrogen in the center, we have 5 valence electrons; all of the valence electrons are bonding, so that's zero. We have a total of 2, 4, 6, 8; eight bonding valence electrons, divided by 2. Five minus four is plus 1. So we have a formal charge of +1 on this Nitrogen right here. The formal charge on the Oxygen turns out to be zero.

We can calculate the formal charges on the other Lewis structures for N2O the same way. We want to choose the Lewis structure that has the formal charges closest to zero. So when we look at this up here, this -2, +1: this one's out. So we're not going to look at this one. We're left with these two here which look pretty much the same. We have a +1 and a -1, and a +1 and a -1 here.

What we want to do is choose the Lewis structure that has a formal charge, the negative formal charge on the most electronegative element. Oxygen is more electronegative than Nitrogen, so we don't want to choose this one here. Here we have that negative charge on Oxygen, which is more electronegative.

That's going to make this the best Lewis structure. This is Dr. B., and thanks for watching.