Oct. 25, 2013
Chapter 6: Fundamentals of Chemical Bonding
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Section 6.1 (Pages 258-263): Overview of Bonding
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The Hydrogen Molecule
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Bond Length and Bond Energy
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Other Diatomic Molecules: F
2
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Unequal Electron Sharing
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Electronegativity and Polar Covalent Bonds
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Suggested end-of-chapter exercises: 6.1, 6.2, 6.5, 6.8, 6.9, 6.10,
6.11
Oct. 25, 2013
Chapter 6: Fundamentals of Chemical Bonding
•
Section 6.2 (Pages 264-274): Lewis Structures
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The Conventions
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The Bonding Framework
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Building Lewis Structures
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Optimizing the Structure
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Beyond the Octet
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Resonance Structures
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Suggested end-of-chapter exercises: 6.15, 6.17, 6.19, 6.21, 6.23,
6.25, 6.27, 6.29
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Lewis Theory: refers to a description of chemical bonding
through Lewis symbols and Lewis structures in accordance
with a particular set of rules.
–
Based on the observed “inertness” of noble gases, and the idea that
atoms of other elements combine to acquire noble gas electron
configuration
Lewis Theory: An Overview
Gilbert Newton Lewis
(1875
–
1946)
Alpha Chi Sigma Educational Foundation:
•
Lewis Theory Fundamentals:
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Valence shell electrons play an important role in chemical bonding
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Electrons are transferred or shared
between two atoms in a way
that both atoms acquire a stable electron configuration.
•
This configuration is normally consistent with noble gas configuration
with an octet (eight) outer-shell electrons.
–
Bonds can be:
•
Ionic
•
Covalent
Lewis Theory: An Overview
•
Octet: refers to eight electrons in the outer-most (valence)
electronic shell of an atom or in a Lewis structure.
•
Lewis Symbol:
represents the valence electrons of an
element by dots placed around the chemical symbol of the
element.
Lewis Theory: An Overview
N
••
•
•
•
P
••
•
•
•
As
••
•
•
•
Sb
••
•
•
•
Bi
••
•
•
•
••
Al
•
•
•
Se
•
•
•
••
Ar
••
••
••
I
•
••
••
••
Problem:
Write Lewis symbols for:
(a)
Mg
(b)
K
(c)
Br
-
(d)
S
2-
Lewis Theory: An Overview
•
Ionic bond: results from the transfer of electrons between
metal and nonmetal atoms.
Positive and negative ions are
formed and held together by electrostatic attractions.
Lewis Theory: An Overview
•
Lewis Structure: combination of Lewis symbols that depicts
the transfer or sharing of electrons in a chemical bond.
Lewis Theory: An Overview
Lewis symbols
Lewis structure
•
Lewis symbols for ionic compounds
Lewis Theory: An Overview
Ba
•
•
O
•
••
•
••
••
O
••
••
••
Ba
2+
2-
Mg
•
•
Cl
•
••
••
••
Cl
•
••
••
••
••
Cl
••
••
••
Mg
2+
-
2
BaO
MgCl
2
Lewis Theory: An Overview
Problem:
Write Lewis structures for the following ionic
compounds:
(a)
Al
2
O
3
(b)
Na
2
S
(c)
Li
2
O
•
Covalent bonds: are formed when electrons are shared
between a pair of atoms.
Lewis Theory: An Overview
•
Covalent bonds: are formed
when electrons are shared
between a pair of atoms.
Lewis Theory: An Overview
