copyright©2000 by houghton mifflin company. all rights reserved. 1 covalent bonding: hybrid atomic...

Copyright©2000 by Houghton Mifflin Company. All rights reserved.

1

Covalent Bonding: Hybrid Atomic Orbitals


2

Bonding

– Write Lewis Structures.

– Determine the Arrangement of e- pairs using VSEPR Theory.

– Determine the hybrid atomic orbitals used to form bonds.


3

Hybridization

• The mixing of atomic orbitals to form special orbitals for bonding.

• The atoms are responding as needed to give the minimum energy for the molecule.


4

Hybrid Orbitals

• Orbitals used to describe bonding that are obtained by taking combinations of atomic orbitals of the isolated atoms.


5

Figure 9.1(a) Lewis Structure (b) Tetrahedral Molecular Geometry of the Methane Molecule

By experiment, CH4 know to be tetrahedral with bond angles of 109.5.

Experiments show 4 equivalent bonds.


6

• Valence electrons of carbon:

2s2 2p2


7

Figure 9.2

The Valence Orbitals on a Free Carbon Atom: 2s, 2px, 2py, and 2pz

• Bonding assumed to involve only the valence electrons.

• Overlap with these orbitals would not give 109.5 bond angles.


8

Hybridization

• ☻☻☻

• A new set of atomic orbitals might better serve the C atom in forming molecules.


9

Hybridization

• ☻☻☻

• Hybridization = Modification of model to account for the observation.

• Atoms seem to use special orbitals when forming molecules.


10

Figure 9.3

The Formation of sp3 Hybrid Orbitals

“sp3 hybridization.”


11

Figure 9.5

An Energy-Level Diagram Showing the Formation of Four sp3 Orbitals

Four equivalent carbon orbitals.


12

Figure 9.6

Tetrahedral Set of Four sp3 Orbitals


13

Figure 9.7

The Nitrogen Atom in Ammonia is sp3 Hybridized


14

Ethylene

• H2C==CH2

• Each carbon atom is surrounded by three effective pairs.

• Requires a set of 3 orbitals with a trigonal planar geometry and 120 bond angles.


15

Figure 9.8

The Hybridization of the s, px, and py Atomic Orbitals


16

Figure 9.9

An Orbital Energy-Level Diagram for sp2 Hybridization

One 2p orbital of carbon is not used..


17

Figure 9.10

An sp2 Hybridized C Atom


18

(sigma) bonds


19

Figure 9.11

The Bonds in Ethylene


20

Double Bond

• Double bond results from an additional bond----- a (pi) bond.


21

Figure 9.12

Sigma and Pi Bonding


22

Figure 9.13

The Orbitals for C2H4


23

Whenever an atom is surrounded by3 effective e- pairs,

a set of sp2 hybrid orbitals is required.


24

• A sigma () bond centers along the internuclear axis.

• A pi () bond occupies the space above and below the internuclear axis.

CCH H

HH

Double Bonds


25

CO2

• O==C==O

• 2 effective pairs around central atom at an angle of 180


26

Figure 9.14

When One s Orbital and One p Orbital are Hybridized, a Set of Two sp Orbitals

Oriented at 180 Degrees Results


27

Figure 9.16

The Orbital Energy-Level Diagram for the Formation of sp Hybrid Orbitals on Carbon

A set of two sp orbitals.


28

Figure 9.17

The Orbitals of an sp Hybridized Carbon Atom

Two sp hybridizedorbitals.

Two p unhybrizedOrbitals.


29

Sigma Bonds


30

Figure 9.19

The Orbitals for CO2


31

PCl5

• 5 e- pairs requires a geometry of

trigonal bipyramidal.

• Requires dsp3 hybridization.


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Figure 9.21

A Set of dsp3 Hybrid Orbitals on a Phosphorus Atom


33

Each Cl is surrounded by 4 e- pairs.

They require sp3 hybridization.


34

Figure 9.22

(a) The Structure of the PCl5 Molecule (b) The Orbitals Used to Form the Bonds in PCl5


35

SF6

• 6 e- pairs requires a geometry of

octahedral.

• Requires d2sp3 hybridization.


36

Figure 9.23An Octahedral Set of d2sp3 Orbitals on a Sulfur Atom


37

The Localized Electron Model

Draw the Lewis structure(s)

Determine the arrangement of electron pairs (VSEPR model).

Specify the necessary hybrid orbitals.

copyright©2000 by houghton mifflin company. all rights reserved. 1 covalent bonding: hybrid atomic...

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valence orbitals

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2s2 2p2 copyright2000

new set of atomic orbitals

hybridization hybridization

bond angles

additional bond