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Part 08 Intermolecular Forces of Attraction. 1.IMFA Intermolecular forces of attraction are any attraction that exists in BETWEEN two or more molecules. They are NOT bonds. 2.Types of IMFA a. London Dispersion Forces - PowerPoint PPT Presentation
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Part 08Intermolecular Forces
of Attraction
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1. IMFAIntermolecular forces of attraction are any attraction that exists in BETWEEN two or more molecules.They are NOT bonds.
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2. Types of IMFAa. London Dispersion Forces
Weak forces of attraction that exist between two or more nonpolar molecules.
Rule: The more electrons in the nonpolar molecule, the stronger the London forces.
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C H
H
H
H
+ -CH
H
H
H
+-
When the molecules are close, their electron clouds experience a momentary shift of electrons producing an instantaneous induced dipole.
LF
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Example:Diagram the London forces between two fluorine molecules and between two iodine molecules.Indicate which substance has the greater London forces.
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F F
F F
+
+
-
-
London Forces
I I+
+
-
-
London Forces
I I
F2 18 electrons I2 126 electronsGreater LF
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b. Dipole-Dipole AttractionsStronger forces of
attraction that exist between two or more polar molecules.
Rule: The more polar the molecule, the stronger the dipole-dipole attractions.
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Example:Diagram the London forces between two hydrogen chloride molecules and between two hydrogen bromide molecules.Indicate which substance has the greater dipole-dipole attractions.
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H Cl+-+
-
HCl+-
- +
EN = 1.4
DPDP
H Br+-+
-
HBr+-
- +
EN = 0.7
DPDP
More PolarStronger DPDP
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c. Hydrogen BondingVery strong force of
attraction between a hydrogen bonded to a fluorine, oxygen or nitrogen in one molecule for a fluorine, oxygen or nitrogen bonded to a hydrogen in another molecule.
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H F+-+
-
HF+-
- +
EN = 1.9VERY Polar Bonds
Hydrogen BondingHydrogen has FON in BOTH molecules.
HB
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+-H O
H
-
+
+-H O
H
-
+
EN = 1.4Polar Bonds
HB
Hydrogen BondingHydrogen has FONin BOTH molecules.
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+-
HN
H
H
-
+
EN = 0.9Polar Bonds
+-
HN
HH
-
+
HB
Hydrogen BondingHydrogen has FONin BOTH molecules.
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p. 781.
BrBrNonpolar MoleculeLondon Forces
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2.
H S
H Nonpolar MoleculeLondon Forces
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3.
H P
H
H
Nonpolar MoleculeLondon Forces
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4.
H Ge
H
H
H
Nonpolar MoleculeLondon Forces
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5. Polar Molecule
Dipole-Dipole
Cl S
Cl+-
+
-
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1.
Page 82
Se C Se
Nonpolar MoleculeLondon Forces
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2.
AsCl
ClCl
Cl
Cl
+-
Nonpolar MoleculeLondon Forces
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3.
B
I
II
+
-
Nonpolar MoleculeLondon Forces
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4.
N O+ -
+
-
Polar MoleculeDipole-Dipole
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5.
F Rn F+ -
Nonpolar MoleculeLondon Forces
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p. 86
1. FBr + -
+
-
Polar MoleculeDipole-Dipole
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2.
B
Br
BrBr
+
-
Nonpolar MoleculeLondon Forces
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3.
Ge ClCl
Cl
Cl
+ -
Nonpolar MoleculeLondon Forces
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Nonpolar MoleculeLondon Forces
4.
AsBr
BrBr
Br
Br
+-
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Nonpolar MoleculeLondon Forces
5.
SF
F
FF
FF
-
+
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Nonpolar MoleculeLondon Forces
6.
Se P
Se
