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.
