Chemical Bonding Molecular Structure
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Chemical Bonding and
Molecular Structure
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I. Structure of Matter (20%)
B. Chemical bonding
1. Binding forces
a. Types: ionic, covalent, metallic, hydrogen bonding, van der Waals
(including London dispersion forces)
c. Polarity of bonds, electronegativities
2. Molecular models
a. Lewis structures
TYPES OF CHEMICAL BONDING
Ionic Bonding
- two atoms of opposite charge electrically attracted to one another
Covalent Bonding
- two atoms each sharing electrons within a molecular orbital
Metallic Bonding
- positive metal ions held together in a lattice with a “sea of electrons”
An actual chemical bond is a blend of all three types of bonding. Most often, one type is dominant over others. We will concentrate on ionic and covalent bonding.
LEWIS STRUCTURES
Only valence electrons are important in bonding.
Lewis dot structures show valence electrons surrounding atom.
We visualize the four valence orbitals of an atom as the sides of a box. Electrons are put into orbitals according to Hund’s rule.
Examples
Be has 2 valence electrons.
Therefore Lewis structure is
Be
N has 5 valence electrons.
Therefore Lewis structure is
N
Br has 7 valence electrons.
Therefore Lewis structure is
C has 4 valence electrons.
Therefore Lewis structure is
Br
C
OCTET RULE – Generally atoms prefer electron configurations with 8 valence electrons. Atoms bond with each other so that every atom has 8 electrons in its outer shell.
- Atoms may take electrons from each other or they may share electrons.
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IONIC BONDING
- Oppositely charged ions attract each other.
- Metal atoms lose e- and nonmetal atoms gain e-.
- Ions attract each other to form ionic lattice.
Lewis structures can be used to illustrate ionic bonding.
Consider Calcium and Fluorine
F
Ca
-
→
+
F
-
Ca2+
F
F
Lewis structures will be much more illuminating when we consider the sharing of electrons (covalent bonding).
Lattice Energy – energy of released when positive and negative ions form crystal lattice due to their
Chemical Bonding and
Molecular Structure
53
I. Structure of Matter (20%)
B. Chemical bonding
1. Binding forces
a. Types: ionic, covalent, metallic, hydrogen bonding, van der Waals
(including London dispersion forces)
c. Polarity of bonds, electronegativities
2. Molecular models
a. Lewis structures
TYPES OF CHEMICAL BONDING
Ionic Bonding
- two atoms of opposite charge electrically attracted to one another
Covalent Bonding
- two atoms each sharing electrons within a molecular orbital
Metallic Bonding
- positive metal ions held together in a lattice with a “sea of electrons”
An actual chemical bond is a blend of all three types of bonding. Most often, one type is dominant over others. We will concentrate on ionic and covalent bonding.
LEWIS STRUCTURES
Only valence electrons are important in bonding.
Lewis dot structures show valence electrons surrounding atom.
We visualize the four valence orbitals of an atom as the sides of a box. Electrons are put into orbitals according to Hund’s rule.
Examples
Be has 2 valence electrons.
Therefore Lewis structure is
Be
N has 5 valence electrons.
Therefore Lewis structure is
N
Br has 7 valence electrons.
Therefore Lewis structure is
C has 4 valence electrons.
Therefore Lewis structure is
Br
C
OCTET RULE – Generally atoms prefer electron configurations with 8 valence electrons. Atoms bond with each other so that every atom has 8 electrons in its outer shell.
- Atoms may take electrons from each other or they may share electrons.
54
IONIC BONDING
- Oppositely charged ions attract each other.
- Metal atoms lose e- and nonmetal atoms gain e-.
- Ions attract each other to form ionic lattice.
Lewis structures can be used to illustrate ionic bonding.
Consider Calcium and Fluorine
F
Ca
-
→
+
F
-
Ca2+
F
F
Lewis structures will be much more illuminating when we consider the sharing of electrons (covalent bonding).
Lattice Energy – energy of released when positive and negative ions form crystal lattice due to their