Chapter 6 Section 5 Molecular Geometry pages 197-207 1 Modern Chemistry Chapter 6 Chemical Bonding...
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Transcript of Chapter 6 Section 5 Molecular Geometry pages 197-207 1 Modern Chemistry Chapter 6 Chemical Bonding...
Chapter 6 Section 5 Molecular Geometry pages 197-207
1
Modern ChemistryChapter 6
Chemical Bonding
Sections 1-5Introduction to Chemical Bonding
Covalent Bonding & Molecular CompoundsIonic Bonding & Ionic Compounds
Metallic BondingMolecular Geometry
Chapter 6 Section 5 Molecular Geometry pages 197-207
2
Chapte
r V
oca
bula
ryVSEPR theoryHybridizationHybrid orbitalsDipoleHydrogen bonding London dispersion
forces
Chapter 6 Section 5 Molecular Geometry pages 197-207
3
Section 5
Molecular Geometry
Chapter 6 Section 5 Molecular Geometry pages 197-207
4
VSEPR Theory•Valence-Shell
Electron-Pair Repulsion
• Repulsions between the set of valence-level electrons surrounding an atom causes these sets to be oriented as far apart as possible.
Chapter 6 Section 5 Molecular Geometry pages 197-207
5
VSPR
E &
Mole
cula
r G
eom
etr
yp.
xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
6
Geom
etr
y &
Lone P
air
s
Chapter 6 Section 5 Molecular Geometry pages 197-207
7
Molecular GeometryLINEAR
Example formula: BeF2
Type of molecule: AB2 Bond angle: 180° Shared pairs on the central atom: 2Unshared pairs on the central atom:
0
- Be -
F::F: :
: :
Chapter 6 Section 5 Molecular Geometry pages 197-207
8
TRIGONAL PLANAR
Example formula: BF3
Type of molecule: AB3 Bond angle: 120° Shared pairs on the central atom: 3Unshared pairs on the central atom:
0
Molecular Geometry
F:::
:F::
:F::
B
Chapter 6 Section 5 Molecular Geometry pages 197-207
9
Molecular GeometryTETRAHEDRAL
Example formula: CH4
Type of molecule: AB4 Bond angle: 109.5° Shared pairs on the central atom: 4Unshared pairs on the central atom:
0
CHH
H
H
Chapter 6 Section 5 Molecular Geometry pages 197-207
10
Molecular GeometryANGULAR
Example formula: H2O
Type of molecule: AB2E2
Bond angle: 105° Shared pairs on the central atom: 2Unshared pairs on the central atom:
2
HO
H
::
Chapter 6 Section 5 Molecular Geometry pages 197-207
11
Molecular GeometryTRIGONAL PYRAMIDAL
Example formula: NH3
Type of molecule: AB3EBond angle: 107° Shared pairs on the central atom: 3Unshared pairs on the central atom:
1
H H
N
:
H
Chapter 6 Section 5 Molecular Geometry pages 197-207
12
Molecular Geometry• Unshared pairs occupies more
space around the central atom than shared pairs
• Unshared pairs repel other electrons more strongly than shared pairs
• Multiple bonds are treated the same as single bonds
• Polyatomic ions are treated like molecules.
Chapter 6 Section 5 Molecular Geometry pages 197-207
13
Molecular Geometry• Try
– CO2
– ClO3 1-
• Practice Problems page 201• Try
– CF4
– NO3 1-
Chapter 6 Section 5 Molecular Geometry pages 197-207
14
Hybridization• The mixing of two or more atomic
orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energy
• Example CH4
C = _ _ __ 1s 2s 2p _ _ _ _ 1s sp3
Chapter 6 Section 5 Molecular Geometry pages 197-207
15
Hybridization• s and p orbitals have different
shapes• The 2s & 2p hybridize to make
four identical orbitals– named sp3
– The 3 is from the three p orbitals used
– But the 1 is not written for the s
Chapter 6 Section 5 Molecular Geometry pages 197-207
16
Hybridization• All sp3 orbitals have the same
energy– Higher than 2s but– Lower than 2p
• Hybrid orbitals – orbitals of equal energy produced by the combination of two or more orbitals.
Chapter 6 Section 5 Molecular Geometry pages 197-207
17
HybridizationN = _ _ _ 1s 2s 2p _ _ _ 1s sp3
O = _ _ 1s 2s 2p _ _ 1s sp3
Chapter 6 Section 5 Molecular Geometry pages 197-207
18
HybridizationBe = 1s 2s _ _ __ 1s spB = _ __ __ 1s 2s 2p _ _ _ __ 1s sp2
Uses one p orbital
Uses two p orbitals
Chapter 6 Section 5 Molecular Geometry pages 197-207
19
Hyb
rid
izati
on
p.
xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
20
Hybri
d O
rbit
al A
nim
ati
on
p. x
x
Chapter 6 Section 5 Molecular Geometry pages 197-207
21
Comparing Molecular & Ionic Compoundsp
. xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
22
Molecule Polarity
• Dipole: created by equal but opposite charges that are separated by a short distance
H - ClLower EN
Higher ENpolar bond =
dipole
2.1
3.0
δ+ δ-
Chapter 6 Section 5 Molecular Geometry pages 197-207
23
Molecule Polarity• Molecule polarity for
compounds with more than one bond depends on …
bond polarity and
molecule geometry.
Chapter 6 Section 5 Molecular Geometry pages 197-207
24
Molecule Polarity1. Draw the Lewis Structure true
to shape. Example NH3
NH
HH
:
Chapter 6 Section 5 Molecular Geometry pages 197-207
25
Molecule Polarity2. Find all the partial positive and
negatives for each atom in the molecule
HH
H
Look at each bond.High EN = δ- Low EN = δ+
δ-
δ+
δ+
δ+
2.1
3.0N
:
Chapter 6 Section 5 Molecular Geometry pages 197-207
26
Molecule Polarity3. Look at around the “outside” of
the molecule.
NH
HH
:
All the same δ = NP; Different δ = P
δ-
δ+
δ+
δ+
Chapter 6 Section 5 Molecular Geometry pages 197-207
27
Molecule Polarity1. Draw the Lewis Structure true
to shape. Example CH4
CH
HH
H
Chapter 6 Section 5 Molecular Geometry pages 197-207
28
Molecule Polarity2. Find all the partial positive and
negatives for each atom in the molecule
Look at each bond.High EN = δ- Low EN = δ+
δ+
δ+
δ+
δ+
2.1
2.5C
HH
H
H
2.12.
1
2.1
δ-
Chapter 6 Section 5 Molecular Geometry pages 197-207
29
Molecule Polarity3. Look at around the “outside” of
the molecule.
δ+
δ+
δ+
δ+
CH
HH
H
δ-
All the same δ = NP; Different δ = PCarbon is not on the “outside”.
Chapter 6 Section 5 Molecular Geometry pages 197-207
30
Intermolecular Forces• The force of attraction between
molecules to make (solids or) liquids
• Boiling point is a good measure of the strength of intermolecular forces
• Weaker than covalent bonds, ionic bonds and metallic bonds
Chapter 6 Section 5 Molecular Geometry pages 197-207
31
Molecule Polarity
Dipole-dipole force: the force of attraction between polar molecules
H - Clδ+ δ-
H - Clδ+ δ-
Chapter 6 Section 5 Molecular Geometry pages 197-207
32
Dip
ole
Dip
ole
Anim
ati
on
p. x
x
Chapter 6 Section 5 Molecular Geometry pages 197-207
33
Comparing Dipole Dipole Forcesp
. xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
34
Hydrogen Bonding• H-F, H-O or H-N bonds have a
large electronegativity difference
• These bonds are very polar.• Molecules with these bonds
have very strong dipole-dipole forces
Chapter 6 Section 5 Molecular Geometry pages 197-207
35
Hyd
rog
en
Bon
din
g
p.
xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
36
Hydrogen Bonding• The intermolecular force in
which a Hydrogen atom that is bonded toNitrogen or Oxygen or Fluorineis attracted to an unshared pair of electronsof the N, O or F of another molecule
Chapter 6 Section 5 Molecular Geometry pages 197-207
37
Hydrogen Bonding• Compare
PH3 & NH3 H2O & H2S Page 204
Chapter 6 Section 5 Molecular Geometry pages 197-207
38
Dip
ole
Induce
d D
ipole
p. x
x
Chapter 6 Section 5 Molecular Geometry pages 197-207
39
Induced Dipole• Polar molecules cause a dipole
in a nonpolar molecule
O
H
H
δ+
δ- O O::
::
::
δ+ δ
+δ-
Chapter 6 Section 5 Molecular Geometry pages 197-207
40
London Dispersion Forces• Nonpolar molecules don’t have
dipoles• However at any instance the
electron distribution may be uneven.
• An instantaneous dipole can occur and induce dipoles in other molecules
Chapter 6 Section 5 Molecular Geometry pages 197-207
41
London D
ispers
ion F
orc
ep.
xx
Chapter 6 Section 5 Molecular Geometry pages 197-207
42
London Dispersion Forces• London dispersion forces – the
intermolecular attraction resulting from the constant motion of electrons and the creation of instantaneous dipoles
• Very weak intermolecular forces• London forces increase with
increasing atomic or molar mass.
Chapter 6 Section 5 Molecular Geometry pages 197-207
43
Lew
is S
truct
ure
s Pra
ctic
e
• C2H4
• BeF2
• AsH3
• IBr
• CHCl3• CN 1-
• N2O2
Chapter 6 Section 5 Molecular Geometry pages 197-207
44
Lew
is S
truct
ure
s Pra
ctic
e
• C2Cl4• SCl2• AsF5
• CI2Cl2• BF3
• NO 1-
• CH2O
• IO3 1-
Chapter 6 Section 5 Molecular Geometry pages 197-207
45
Section 5 Homework
Chapter 6 Section 5 Worksheet