**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__

__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__

__Sp3 Hybridisation__

• Axes of
the four *sp*3 hybrid orbitals are directed toward the corners of a
regular tetrahedron

• *sp*3 hybridization results in bond angles
of approximately 109.5°

• Each *sp*3
orbital has 25% *s*-character and 75% *p*-character

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

• one 2*s
*orbital, three 2*p *orbitals

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

__Sp__^{2}
Hybridisation

__Sp__

^{2}Hybridisation• Bond
angles of approximately 120^{0}

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

• Forms
three equivalent *sp*2 hybrid orbital

• Axes of
the three *sp*2 hybrid orbitals lie in a plane and are directed toward the
corners of an equilateral triangle

• Three
equivalent *sp*2 orbitals along with the remaining unhybridized 2*p *atomic
orbital

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

• One 2s orbital, two 2p orbitals

**Borane
(BH**_{3})

_{3})

• Sp2
hybridization

• Exception
to octet rule

• According
VSEPR theory, trigonal planar with bond angle 120^{0}

Trigonal planar carbon, 120^{o}

__sp hybridization__

__sp hybridization__

• Bond
angle of approximately 180^{0}

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

• Produces
two equivalent *sp *hybrid orbital

• Axes of the
unhybridized 2*p *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 Ï€ 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 Ï€-bonds are formed

• Geometry of ethyne is linear and bond angle is 180°

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