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, 120^o

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°