Chemical Bonding
Types of Bonds
Ionic Bonding
Lewis Structures
Covalent Bonding
Resonance Structures
Octet Rule
Polar Molecules
Molecular Geometries
VSEPR
Basic Shapes
3-D Notation
Hybridization (Lab)
Chemical compounds
Chemical Bonds, Lewis Symbols, and the Octet Rule
• Chemical bond: attractive force holding two or more
atoms together.
• Ionic bond results from the transfer of electrons from a
metal to a nonmetal.
• Covalent bond results from sharing electrons between
the atoms. Usually found between nonmetals.
• Metallic bond attractive force holding pure metals
together.
Ionic Compounds
Ionic Bonds: One Big Greedy Thief Dog!
Covalent Bonding
Polar Covalent Bonds: Unevenly
matched, but willing to share.
Metallic Bonding
Metallic Bonds: Mellow dogs with plenty
of bones to go around.
Covalent Bonding
Chemical Bonds, Lewis Symbols, and the Octet Rule
Lewis Symbols
Drawing Lewis Structures
Follow Step by Step Method
1. Total all valence electrons. [Consider Charge]
2. Write symbols for the atoms and guess skeleton structure
[ define a central atom ].
3. Place a pair of electrons in each bond.
4. Complete octets of surrounding atoms. [ H = 2 only ]
5. Place leftover electrons in pairs on the central atom.
6. If there are not enough electrons to give the central atom
an octet, look for multiple bonds by transferring
electrons until each atom has eight electrons around it.
Exceptions to the Octet Rule
•
•
•
•
Central Atoms Having Less than an Octet
Relatively rare.
Molecules with less than an octet are typical for
compounds of Groups 1A, 2A, and 3A.
Most typical example is BF3, with only 6
Formal charges indicate that the Lewis structure with an
incomplete octet is more important than the ones with
double bonds.
Molecular Shapes: VSEPR
• There are five fundamental geometries for molecular
shape:
Figure 9.3
HyperChem
e-pairs
Notation
Name of VSEPR shape Examples
2
AX2
Linear
HgCl2 , ZnI2 , CS2 , CO2
3
AX3
Trigonal planar
BF3 , GaI3
AX2E
Non-linear (Bent)
SO2 , SnCl2
AX4
Tetrahedral
CCl4 , CH4 , BF4-
AX3E
(Trigonal) Pyramidal
NH3 , OH3-
AX2E2
Non-Linear (Bent)
H2O , SeCl2
AX5
Trigonal bipyramidal
PCl5 , PF5
AX4E
Distorted tetrahedral
(see-sawed)
TeCl4 , SF4
AX3E2
T-Shaped
ClF3 , BrF3
AX2E3
Linear
I3- , ICl2-
AX6
Octahedral
SF6 , PF6-
AX5E
Square Pyramidal
IF5 , BrF5
AX4E2
Square Planar
ICl4- , BrF4-
4
5
6
Timberlake LecturePLUS
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Timberlake LecturePLUS
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Polarity
Molecular
Geometries
and Bonding
Just as electrons push away from
each other, so do molecules
HBr
HBr is a polar molecule: dipole-dipole forces. There are also
dispersion forces between HBr molecules.
CH4
CH4 is nonpolar: London dispersion forces, caused by
“temporary dipoles”.
S
SO2
SO2 is a polar molecule: dipole-dipole forces. There are also
dispersion forces between SO2 molecules.
Intermolecular Forces
What type(s) of intermolecular forces exist between each of
the following molecules?
HBr
HBr is a polar molecule: dipole-dipole forces. There are also
dispersion forces between HBr molecules.
CH4
CH4 is nonpolar: dispersion forces.
S
SO2
SO2 is a polar molecule: dipole-dipole forces. There are also
dispersion forces between SO2 molecules.
Intermolecular Forces
Hydrogen Bond
The hydrogen bond is a special dipole-dipole interaction between
they hydrogen atom in a polar N-H, O-H, or F-H bond and an
electronegative O, N, or F atom.
A
H…B
or
A
A & B are N, O, or F
H…A
Intermolecular Forces
Dispersion Forces
Attractive forces that arise as a result of temporary dipoles
induced in atoms or molecules
ion-induced dipole interaction
dipole-induced dipole interaction