Post on 19-Jan-2016
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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
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Se P
Se