Now, we’re going to say that the opposite of a sigma bond is a pi bond. We’re going
to say a pi bond is a sideways overlapping of p orbitals. And we’re going to say if
you have elements single bonded to each other, you have 1 sigma. Every bond you make is always
a sigma bond. C-C
Let’s say compound has two bonds together. It’s a double bond. Well, it’s going to
have 1 sigma, and 1 pi. C=C
And let’s say compound has three bonds, triple bonds. Again, it’s going to have
1 sigma, and 2 pi bonds. Every extra bond you add, that’s what pi bond be added.
C=C So just remember, here we’re talking about
direct overlapping of atomic orbitals, so we’re talking about the formation of a bond.
A sigma bond. And then we’re going to say if we have a double bond or a triple bond,
those will be pi bonds that we’re adding on top of the sigma bond. They are kind of
like bread that goes around the meat of the bun. The meat portion will be the sigma bond,
bread part adds extra strength to that sigma bond.
Now, what would happen though if we’re trying to form a covalent bond with different atomic
orbitals? For example, we have BeCl2. Now BeCl2 looks
like this. Cl-Be-Cl
Looks like Beryllium is in group 2A, so there are two bound electrons, Chlorine is in group
7A, so it has seven. Halogens are not in the center, only make one bond. But the problem
here is, electron configuration of Beryllium is Helium, 2s2, and Chlorine is [Ne]3s23p5.
And here’s the thing. An s and a p cannot mix together. There are different atomic orbitals.
They have to both be the same letter for them to successfully mix. This is where hybridization
comes into play. Now, hybridization is a way of us mixing our s, our p, and sometimes our
d orbitals together, to make hybrid orbital. That hybrid orbital will have a little bit
of s character, p character, and d character. That will allow the central element to form
bonds with basically any other element. So what’s going to happen here is, for the
Beryllium to form a bond with the Chlorine, it needs to somehow gain a p orbital. So what’s
going to wind up happening here is, in this 2s electron orbital, we’re going to have
a promotion of one of its electrons. So this electron here is actually going to get promoted,
and jump up to the 2p orbital. And as a result, we have now one in the 2s, one in the 2p.
And we’re going to say here, now the way it looks visually is this. And I’m going
to move myself away from shock guide so we have more room to write stuff. So visually
this is the way it looks. We have our electrons in the 2s, remember the shape of s is a sphere.
We want to promote it to the p, and p looks like a dumbbell. Like that. What’s going
to happen like I said is this electron is going to jump over here, and what that really
means is that this p and this s shape are going to mix together, and they are kind of
going to spit out a hybrid baby. This hybrid orbital is going to have a little s character,
a little bit of p character. And as you can notice, it kind of looks like a dumbbell but
one side is a lot bigger than the other side. It’s a hybrid of these two guys here. These
are the parents, and this is their offspring. And because we promoted one electron to the
two p region, we’re going to say that this becomes an sp hybrid orbital. Because it has
one that’s in the s, and one that went to the p. That’s why it’s called sp. But
remember. p has how many electron orbitals? p has three electron orbitals. We only had
enough electron to place only one of them, so these two over here are not being utilized.
We’re going to say those two over here, those two electron orbitals are called unhybridized
orbitals. This is the way bonds form, and if the atomic
orbitals are different letters, they cannot mix together. So to get around this, we’re
going to mix up those orbitals together, forming hybrid orbitals. Since this now has s and
p characteristics, it can form a bond, with Chlorine. Because Chlorine wants something
with p characteristics involved. Since it is hybrid, it does have p characteristics
involved so that’s why we were able to do this. Now hybridization is a little conceptual,
really conceptual, but just remember the basics of this. When it comes to answering questions,
which we’re going to do next, it’s really easy and simple to follow, as long as you
look at it in a very simple way. So just get down to the fundamentals of this. In order
for different atomic orbitals, different letters to connect together, we have to mix and hybridize
the atomic orbitals of the central element. And in that way we can form bonds.