And so when we have three bonding groups we know that the electron pair geometry
is gonna be called trigonal planar.
Because remember we're trying to spread those groups around evenly so
that they are maximizing the distance between them.
So it's trigonal planar.
For our molecular geometry it's still trigonal planar because all of our groups
are bonding groups.
And that's gonna be the case anytime the number of
electron groups equals the number of bonding groups.
So in other words, no non-bonding groups, these two will always be the same.
Now we're gonna look at a different example where you have SO2.
And here we still have three electron groups, but
now we have two bonding and one non-bonding group.
And what we see is that one non-bonding group still affects the position,
it still affects where these two bonding groups are, but when I
look at the electron pair geometry, what I see is that it still trigonal planar.
Because that is based solely on the number of electron groups around the central
atom, regardless of whether they are bonding or non-bonding.
Now when I look at the molecular geometry I have to remember
that there is a lone pair of electrons on that central atom.
And because of that,
it's going to affect the angles between these two other bonding groups.
So one way to think about this is to imagine that you're doing something that
you know you probably shouldn't be doing in the first place.
And you hear this little voice in your head,
it probably sounds a lot like your parents voice.
Maybe your mom or your dad's voice, and it's saying,
you know you shouldn't be doing this.
Well that's what this lone pair is.
We can't really see it, but it's still affecting our behavior.
So we can't see these lone pairs of electrons, but
it's affecting the position of those bonding groups.
And so we describe this as bent.
We can't go to linear because we still have to consider that we have these
non-binding electrons on that central atom.
Now we also have some lone pairs out here on our oxygens.
But the thing to remember there is these are kind of like the voices in somebody
else's head.
They're not affecting the geometry around our central atom or
sulfur in this particular example.