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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