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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.