SP2 Hybridization Explained | Hybridization Tricks

sp2 hybridization explained. In this

lecture, I will explain sp2

hybridization in complete detail with

examples. After watching this video, you

will fully understand how sp2

hybridization works in different

molecules. So, let us begin. First, we

need to understand how we can define sp2

hybridization. The type of hybridization

in which 1 s and 2p atomic orbitals mix

together and form three sp2 hybridized

orbitals is called sp2 hybridization.

Now before we move further, there is one

important rule about hybridization that

you must always keep in mind. The rule

is that the number of atomic orbitals

that mix together will always be equal

to the number of hybrid orbitals that

are formed. For example, here in sp2

hybridization, one s orbital and two p

orbitals are mixing together. That means

three atomic orbitals are mixing. So

according to this rule, three hybrid

orbitals will always be formed. And you

need to keep in mind that this rule

applies to every type of hybridization.

Now I will tell you about the shapes of

these orbitals. As we know the shape of

S orbital is spherical and the shape of

P orbital is dumbbell. When we look at

this through a diagram, one S orbital

which has spherical shape mixes with two

P orbitals which are PX orbital and PY

orbital. These three orbitals mix

together and form three sp2 hybridized

orbitals. If we look at the overall

shape of these sp2 hybrid orbitals,

their arrangement is trional planar. To

understand sp2 hybridization in complete

detail, we will cover three examples. In

the first example, we will understand

sp2 hybridization in BF3. In the second

example, we will see sp2 hybridization

in ethine molecule. And in the third

example, we will cover sp2 hybridization

in benzene. Let's start with the first

example. If we look at the BF3 molecule

as it is clear from the formula, the

central atom here is boron and three

florine atoms have formed bonds with

boron. Now before explaining the

electronic configuration, I will share a

very useful trick with you. Using this

trick, you can find the hybridization of

any specific atom in any molecule very

quickly. The trick is this. First write

the expanded structure of the molecule.

Expanded structure means open all the

bonds and write them separately. Then

count all those bonds. The number you

get will be the steric number of that

atom. And the hybridization type in

which the number of hybrid orbitals

equals that steric number will be the

hybridization of that atom. Let's apply

this trick on boron in BF3. When we

write the expanded structure of BF3, it

becomes clear that boron is forming

three bonds, one bond with each florine

atom. So the steric number of boron is

three. Now sp2 hybridization gives us

three hybrid orbitals. Therefore the

hybridization of boron in BF3 is sp2.

Now look at the electronic configuration

of boron. The atomic number of boron is

five. This means boron has five

electrons. The ground state electronic

configuration of boron is 1 s2 2 s2 2

px1 2 2 p y0 2 2 pz0

in this ground state. Boron has only one

unpaired electron. But boron needs to

form three bonds with three florine

atoms. So boron needs three unpaired

electrons. To get three unpaired

electrons, one electron from the 2s

orbital gets excited. This electron

moves from 2s orbital and goes into the

empty 2py orbital. Now the excited state

electronic configuration of boron

becomes 1 s2 2 s1 2px1 2py1 2pz 0. Here

always remember one important point. The

electron will always be excited from the

2s orbital only. The electron from 1 s

orbital will never get excited. The

reason is that 1 s is not the valence

shell of boron. Only valence shell

electrons participate in hybridization

and bonding. Now hybridization takes

place. The s orbital and the 2p orbitals

which are 2px and 2py mix together.

According to the rule of hybridization,

three sp2 hybrid orbitals are formed.

These three sp2 orbitals form three

bonds with three florine atoms. The

shape of BF3 molecule is trional planar

and the bond angle in BF3 is 120°. Now

let's move to the second example that is

the ethine molecule. In eene the central

atom is carbon. Let us apply the same

trick here. First write the expanded

structure of aine. When we open the

structure of ethine it becomes clear

that each carbon is forming a double

bond with the other carbon and along

with that each carbon also has two

hydrogen atoms attached to it. Now if we

count the characters of carbon we have

two single bonds with two hydrogen atoms

and one double bond with the other

carbon. These make a total of three

characters for carbon. So the steric

number of carbon is three. And since sp2

hybridization gives three hybrid

orbitals, the hybridization of carbon in

ethine is sp2. Now let's look at the

electronic configuration of carbon. The

atomic number of carbon is six. The

ground state electronic configuration of

carbon is 1 s2 2 s2 2 px1 2 p y1 2 pz0.

In this ground state, carbon already has

two unpaired electrons in two px and 2py

orbitals. But for sp2 hybridization,

carbon needs three unpaired electrons.

So one electron from 2s orbital gets

excited and moves into the empty 2pz

orbital. Now the excited state

electronic configuration of carbon

becomes 1 s2 2 s1 2 px1 2 p y1 2 pz1.

Now hybridization takes place. The 2 S

orbital and two px and two py orbitals

mix together to form 3 spp2 hybrid

orbitals. The 2 pz orbital does not take

part in hybridization. It remains

unhybridized and forms the pi bond in

the double bond of ethine. The shape

around each carbon atom in ethine is

trional planar and the bond angle is

120°. Now let's move towards the third

example that is benzene. In benzene, the

carbon atom shows sp2 hybridization. Let

us apply the trick here as well. Write

the expanded structure of benzene. In

benzene, each carbon atom has one

hydrogen atom attached to it. Along with

that, each carbon is connected to two

other carbon atoms. One with a single

bond and one with a double bond. So, if

we count the characters of carbon in

benzene, there is one bond with

hydrogen, one single bond with adjacent

carbon and one double bond with the

other adjacent carbon. This gives us a

total of three characters. So the steric

number is three and therefore the

hybridization of carbon in benzene is

sp2. Now the ground state electronic

configuration of carbon is the same as

we discussed in athen. It is 1 s2 2 s2

2px1 2p y1 2pz 0. And just like in a one

electron from 2s orbital gets excited

and moves into the empty 2pz orbital.

The excited state configuration becomes

1 s2 2 s1 2 px1 2 p y1 2 pz1. After

excitation, the same hybridization

process takes place. The 2 s 2 px and

2py orbitals mix together to form 3 s p2

hybrid orbitals. The two pz orbital

remains unhybridized and participates in

the deoized pi bonding system of

benzene. The shape around each carbon

atom in benzene is also trigonal planar

and the bond angle is 120°. Now at the

end, let me give you a quick summary of

this entire lecture. Sp2 hybridization

occurs when 1 s orbital and 2 p orbitals

mix together to form three sp2 hybrid

orbitals. The shape of sp2 hybridized

molecules is trional planer with a bond

angle of 120°. We also learned an

important trick. Write the expanded

structure of any molecule. Count the

total bonds or characters of the central

atom and that number will tell you the

hybridization. If the number is three,

the hybridization will be sp2. We

studied three examples. In BF3, boron

underos excitation from ground state and

then sp2 hybridization occurs. In athen

and benzene carbon also underos

excitation from 2s to 2pz and then sep

hybridization takes place. In all three

cases the shape is tragonal planar and

bond angle is 120°. Remember the rule of

hybridization. The number of orbitals

that go in will always equal the number

of hybrid orbitals that come out. This

concept is very important for your

exams. Practice these examples and you

will master sp2 hybridization

completely.