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Welcome to CHM 1220/1225
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Today’s Plan
Announcements
Complete Chapter 10
•
Pre-lecture Assignment 12 will be
available at 2:00 p.m. today and is due by
noon, Friday, October 5, 2007.
•
Chapter 10 Quiz is due by noon, Friday,
October 5, 2007.
•
Chapter 10 Homework is due by 12:50
p.m. Friday, October 5, 2007
Chapter 10
Molecular
Geometry and
Chemical Bonding
Theory
Molecular Geometry and Chemical
Bonding Theory
Molecular Geometry and Directional Bonding
1.
The Valence-Shell Electron-Pair Repulsion
(VSEPR) Model
2.
Dipole Moment and Molecular Geometry
3.
Valence Bond Theory
4.
Description of Multiple Bonding
Molecular Orbital Theory
5.
Principles of Molecular Orbital Theory
6.
Electron Configurations of Diatomic Molecules
of the Second Period
7.
Molecular Orbitals and Delocalized Bonding

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Valence bond theory is an approximate theory to
explain the electron pair or covalent bond by
quantum mechanics.
A bond forms when
An orbital on one atom comes to occupy a portion
of the same region of space as an orbital on the
other atom. The two orbitals are said to overlap.
The total number of electrons in both orbitals is no
more than two.
The greater the orbital overlap, the stronger the
bond.
The greater the orbital overlap, the stronger the
bond.
Orbitals (except
s
-orbitals) bond in the direction in
which they protrude or point, to obtain maximum
overlap.
Hybrid orbitals are orbitals used to describe the
bonding that are obtained by taking combinations
of atomic orbital of the isolated atoms.
The number of hybrid orbitals formed always
equals the number of atomic orbitals used.
Hybrid orbitals are named by using the atomic
orbitals that combined:
one
s
-orbital + one
p
-orbital give two
sp
-orbitals
one
s
-orbital + two
p
-orbital give three
sp
2
-orbitals
one
s
-orbital + three
p
-orbital give four
sp
3
-orbitals
one
s
-orbital + three
p
-orbital + one
d
-orbital give
five
sp
3
d
-orbitals
one
s
-orbital + three
p
-orbital + two
d
-orbital give
six
sp
3
d
2
-orbitals
Hybrid orbitals have definite directional
characteristics as described in the table below.