Drawing the Lewis Structure for NH3

Viewing Notes:

  • NH3 (Ammonia) is a commonly tested Lewis structure. It's not particularly difficult but is an important structure.
  • In the NH3 Lewis structure (and all structures), hydrogen goes on the outside. Remember, too, that hydrogen only needs two valence electrons to have a full outer shell.
  • In the Lewis structure for NH3 there are a total of 8 valence electrons. Three pairs will be used in the chemical bonds between the N and H and one pair of electrons will be unbonded.

Transcript: OK, this is Dr. B. We're going to do the Lewis structure for NH3: ammonia or Nitrogen trihydride. On the periodic table, Nitrogen is in group 5 or 15 so it has 5 valence electrons, and then Hydrogen is in group 1. It has one valence electron, but we have 3 Hydrogens, so let's mutiply that by 3. Five plus 3, a total of 8 valence electrons.

Hydrogen always goes on the outside, so let's put our Nitrogen right here, and let's put some Hydrogens around it. We have three of them; there they go, 1, 2, 3. And now we have those 8 valence electrons. We're going to form chemical bonds with those. So we'll put them between atoms first. Hydrogen only needs 2 valence electrons to have a full outer shell, so Hydrogens are going to be full with 2 valence electrons. So we have 2, 4, 6, and we have 8 total, let's just put those up here.

And now, if you take a look, we can see that Nitrogen has 8 valence electrons, its octet is full; and each of the Hydrogens, each one of those has 2 valence electrons. So we're good. That's the Lewis structure for NH3. You'll see it drawn a lot as a structural formula. That's going to look like this right here, where these electrons are represented by a line. So the pair of electrons that are bonding, by a line.

And that's it: NH3. This is Dr. B., and thanks for watching.