Hybridisation

Hybridisation

Contents

• Hybridisation

• SP2

• Sp3

• Bong angles

• Geometry

Learning
Objectives

At the end of this
lecture, student will be able to

• Explain different types of hybridisation

• Relate hybridisation to geometry of molecules

Hybridisation

• Hybrid orbital- An orbital formed by the combination of
two or more atomic orbitals

• Hybridization- The combination of atomic orbitals of
different types

• Number of hybrid orbitals formed is equal to the number of
atomic orbitals combined

• sp3 Hybrid Orbitals—Bond Angles of Approximately 109.5°

• Combination of the 2s atomic orbital and three 2p atomic
orbitals forms four equivalent sp3 hybrid orbitals

• Mixing of orbitals

• To attain equal energy and stability

• Sp3

• Sp2

• Sp

Sp3
Hybridisation

Axes of
the four sp3 hybrid orbitals are directed toward the corners of a
regular tetrahedron

sp3 hybridization results in bond angles
of approximately 109.5°

Each sp3
orbital has 25% s-character and 75% p-character

Because
those are the percentages of the orbitals combined when constructing them

one 2s
orbital, three 2p orbitals

The four orbitals are directed toward the corners of a
tetrahedron, causing each bond angle to be 109.5°

Sp2
Hybridisation

Bond
angles of approximately 1200

Combination
of one 2s atomic orbital wave function and two 2p atomic orbital

Forms
three equivalent sp2 hybrid orbital

Axes of
the three sp2 hybrid orbitals lie in a plane and are directed toward the
corners of an equilateral triangle

Three
equivalent sp2 orbitals along with the remaining unhybridized 2p atomic
orbital

• Each sp2 orbital has 33% s-character and 67% p-character

• One 2s orbital, two 2p orbitals

Borane
(BH3)

Sp2
hybridization

Exception
to octet rule

According
VSEPR theory, trigonal planar with bond angle 1200

Trigonal planar carbon, 120o

sp hybridization

Bond
angle of approximately 1800

Combination
of one 2s atomic orbital and one 2p atomic orbital

Produces
two equivalent sp hybrid orbital

Axes of the
unhybridized 2p atomic orbitals are perpendicular to each other and to
the axis of the two sp hybrid orbitals

Each sp
orbital has 50% s-character and 50% p-character

Summary

• Sp3, sp2   and sp
hybridisation

• Example for Sp3 hybridisation is methane and ethane

• Four Sp3 hybridized orbitals

• All bonds are sigma bonds

• Geometry of methane is tetrahedral and bond angle is
109.5°

• Example for sp2 hybridisation is ethene

• Three Sp2 hybridized orbitals

• One unhybridised p- orbital oriented perpendicular to the
plane

• One π bond is formed

• Geometry of ethene is trigonal and bong angle is 120°

Example
for sp hybridisation is ethyne

Two Sp
 hybridized orbitals

Two
unhybridised P- orbitals oriented pependicular to the plane

Two π-bonds are formed

Geometry
of ethyne is linear and bond angle is 180°

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