1 © 2006 brooks/cole - thomson chemistry and chemical reactivity 6th edition john c. kotz paul m....
TRANSCRIPT
![Page 1: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/1.jpg)
1
© 2006 Brooks/Cole - Thomson
Chemistry and Chemical Reactivity 6th Edition
John C. Kotz Paul M. Treichel
Gabriela C. Weaver
CHAPTER 9
Bonding and Molecular Structure:Fundamental Concepts
© 2006 Brooks/Cole Thomson
Lectures written by John Kotz
cellE
![Page 2: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/2.jpg)
2
© 2006 Brooks/Cole - Thomson
Chemical Bonding
Problems and questions —How is a molecule or
polyatomic ion held together?
Why are atoms distributed at strange angles?
Why are molecules not flat?Can we predict the structure?How is structure related to
chemical and physical properties?
![Page 3: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/3.jpg)
3
© 2006 Brooks/Cole - Thomson
Structure & Bonding
NN triple bond. Molecule is unreactive
Phosphorus is a tetrahedron of P atoms. Very reactive!
Red phosphorus, a polymer. Used in matches.
![Page 4: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/4.jpg)
4
© 2006 Brooks/Cole - Thomson
Forms of Chemical Bonds
• There are 2 extreme forms of connecting or bonding atoms:
• Ionic—complete transfer of 1 or more electrons from one atom to another
• Covalent—some valence electrons shared between atoms
• Most bonds are somewhere in between.
![Page 5: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/5.jpg)
5
© 2006 Brooks/Cole - Thomson
Ionic CompoundsMetal
Nonmetal
2 Na(s) + Cl2(g) ---> 2 Na+ + 2 Cl-
![Page 6: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/6.jpg)
6
© 2006 Brooks/Cole - Thomson
Covalent BondingThe bond arises from the mutual attraction of
2 nuclei for the same electrons. Electron sharing results.
Bond is a balance of attractive and repulsive forces.
![Page 7: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/7.jpg)
7
© 2006 Brooks/Cole - Thomson
Bond FormationA bond can result from a “head-to-head”
overlap of atomic orbitals on neighboring atoms.
ClH H Cl••
••
••
••
••
••
+
Overlap of H (1s) and Cl (3p)
Note that each atom has a single, unpaired electron.
![Page 8: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/8.jpg)
8
© 2006 Brooks/Cole - Thomson
Chemical Bonding: Objectives
Objectives are to understand:
1. valence e- distribution in molecules and ions.
2. molecular structures3. bond properties and their
effect on molecular properties.
![Page 9: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/9.jpg)
9
© 2006 Brooks/Cole - Thomson
Electron Distribution in Molecules
• Electron distribution is
depicted with Lewis electron dot structures
• Valence electrons are distributed as shared or BOND PAIRS and unshared or LONE PAIRS.
G. N. Lewis 1875 - 1946
![Page 10: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/10.jpg)
10
© 2006 Brooks/Cole - Thomson
Bond and Lone Pairs• Valence electrons are distributed as
shared or BOND PAIRS and unshared or LONE PAIRS.
•
••
•
••
H Cllone pair (LP)
shared orbond pair
This is called a LEWIS ELECTRON DOT structure.
![Page 11: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/11.jpg)
11
© 2006 Brooks/Cole - Thomson
Valence ElectronsElectrons are divided between core and valence
electronsB 1s2 2s2 2p1
Core = [He] , valence = 2s2 2p1
Br [Ar] 3d10 4s2 4p5
Core = [Ar] 3d10 , valence = 4s2 4p5
![Page 12: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/12.jpg)
12
© 2006 Brooks/Cole - Thomson
Rules of the GameNo. of valence electrons of a main
group atom = Group number
•For Groups 1A-4A, no. of bond pairs = group number.
• For Groups 5A -7A, BP’s = 8 - Grp. No.
![Page 13: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/13.jpg)
13
© 2006 Brooks/Cole - Thomson
Rules of the Game•Except for H (and sometimes atoms of 2nd and 3rd families and 3rd and higher periods),
BP’s + LP’s = 4
This observation is called the
OCTET RULE
![Page 14: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/14.jpg)
14
© 2006 Brooks/Cole - Thomson
Building a Dot StructureAmmonia, NH3
1. Decide on the central atom; never H. Central atom is atom of lowest affinity
for electrons. Therefore, N is central2. Count valence electrons H = 1 and N = 5 Total = (3 x 1) + 5 = 8 electrons / 4 pairs
![Page 15: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/15.jpg)
15
© 2006 Brooks/Cole - Thomson
3. Form a single bond between the central atom and each surrounding atom
H H
H
N
Building a Dot Structure
H••
H
H
N4. Remaining electrons form LONE PAIRS to complete octet as needed.
3 BOND PAIRS and 1 LONE PAIR.
Note that N has a share in 4 pairs (8 electrons), while H shares 1 pair.
![Page 16: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/16.jpg)
16
© 2006 Brooks/Cole - Thomson
10 pairs of electrons are now left.
Sulfite ion, SO32-
Step 1. Central atom = SStep 2. Count valence electrons
S = 6 3 x O = 3 x 6 = 18 Negative charge = 2
TOTAL = 26 e- or 13 pairsStep 3. Form bonds
![Page 17: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/17.jpg)
17
© 2006 Brooks/Cole - Thomson
Sulfite ion, SO32-
Remaining pairs become lone pairs, first on outside atoms and then on central atom.
O O
O
S••
••
••
••
•• ••
••
••
••
••
Each atom is surrounded by an octet of electrons.
![Page 18: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/18.jpg)
18
© 2006 Brooks/Cole - Thomson
Carbon Dioxide, CO2
1. Central atom = _______2. Valence electrons = __ or __ pairs3. Form bonds.
4. Place lone pairs on outer atoms.
This leaves 6 pairs.
![Page 19: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/19.jpg)
19
© 2006 Brooks/Cole - Thomson
Carbon Dioxide, CO2
4. Place lone pairs on outer atoms.
The second bonding pair forms a pi (π) bond.
5. So that C has an octet, we shall form DOUBLE BONDS between C and O.
![Page 20: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/20.jpg)
20
© 2006 Brooks/Cole - Thomson
Double and even triple bonds are commonly observed for C, N, P, O, and S
H2CO
SO3
C2F4
![Page 21: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/21.jpg)
21
© 2006 Brooks/Cole - Thomson
Sulfur Dioxide, SO2
1. Central atom = S2. Valence electrons = 18 or 9 pairs
bring inleft pair
OR bring inright pair
3. Form double bond so that S has an octet — but note that there are two ways of doing this.
•• OS
••
••
••
••••••O
![Page 22: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/22.jpg)
22
© 2006 Brooks/Cole - Thomson
Sulfur Dioxide, SO2
This leads to the following structures.
These equivalent structures are called RESONANCE STRUCTURES. The true electronic structure is a HYBRID of the two.
![Page 23: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/23.jpg)
23
© 2006 Brooks/Cole - Thomson
Formal Atom Charges
• Atoms in molecules often bear a charge (+ or -). • The predominant resonance structure of a
molecule is the one with charges as close to 0 as possible.
• Formal charge = Group number – 1/2 (no. of bonding electrons)
- (no. of LP electrons)
![Page 24: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/24.jpg)
24
© 2006 Brooks/Cole - Thomson
••
••O OC
••••
+4 - (1/2)(8) - 0 = 0
+6 - (1/2)(4) - 4 = 0
Carbon Dioxide, CO2
![Page 25: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/25.jpg)
25
© 2006 Brooks/Cole - Thomson
Thiocyanate Ion, SCN-
6 - (1/2)(2) - 6 = -1 5 - (1/2)(6) - 2 = 0
4 - (1/2)(8) - 0 = 0
••
•
••S NC
•••
![Page 26: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/26.jpg)
26
© 2006 Brooks/Cole - Thomson
Thiocyanate Ion, SCN-
••
•
••S NC
•••
••
•
••S NC
•••
•••
••S NC
•••
Which is the most important resonance form?
![Page 27: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/27.jpg)
27
© 2006 Brooks/Cole - Thomson
Calculated Partial Charges in SCN-
All atoms negative, but most on the S
••
•
••S NC
•••
![Page 28: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/28.jpg)
28
© 2006 Brooks/Cole - Thomson
Violations of the Octet Rule
Usually occurs with B and elements of higher periods.
BF3 SF4
![Page 29: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/29.jpg)
29
© 2006 Brooks/Cole - Thomson
Boron Trifluoride• Central atom = _____________• Valence electrons = __________ or
electron pairs = __________• Assemble dot structure
The B atom has a share in only 6 pairs of electrons (or 3 pairs). B atom in many molecules is electron deficient.
![Page 30: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/30.jpg)
30
© 2006 Brooks/Cole - Thomson
Boron Trifluoride, BF3
What if we form a B—F double bond to satisfy the B atom octet?
F••
••
••
F
F
B••
••
••
••
••
+1
-1
![Page 31: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/31.jpg)
31
© 2006 Brooks/Cole - Thomson
Sulfur Tetrafluoride, SF4• Central atom =
• Valence electrons = ___ or ___ pairs.• Form sigma bonds and distribute electron
pairs.
5 pairs around the S atom. A common occurrence outside the 2nd period.
![Page 32: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/32.jpg)
MOLECULAR GEOMETRY
![Page 33: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/33.jpg)
33
© 2006 Brooks/Cole - Thomson
VSEPR • Valence Shell Electron
Pair Repulsion theory.• Most important factor in
determining geometry is relative repulsion between electron pairs.
Molecule adopts the shape that minimizes the electron pair repulsions.
MOLECULAR GEOMETRY
![Page 34: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/34.jpg)
34
© 2006 Brooks/Cole - Thomson
Electron Pair GeometriesActive Figure 9.8
![Page 35: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/35.jpg)
35
© 2006 Brooks/Cole - Thomson
![Page 36: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/36.jpg)
36
© 2006 Brooks/Cole - Thomson
![Page 37: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/37.jpg)
37
© 2006 Brooks/Cole - Thomson
![Page 38: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/38.jpg)
38
© 2006 Brooks/Cole - Thomson
Electron Pair GeometriesActive Figure 9.8
![Page 39: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/39.jpg)
39
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRAmmonia, NH3
1. Draw electron dot structure2. Count BP’s and LP’s = 4
H••
H
H
N
3. The 4 electron pairs are at the corners of a tetrahedron.
![Page 40: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/40.jpg)
40
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRAmmonia, NH3
There are 4 electron pairs at the corners of a tetrahedron.
The ELECTRON PAIR GEOMETRY is tetrahedral.
![Page 41: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/41.jpg)
41
© 2006 Brooks/Cole - Thomson
Ammonia, NH3
The electron pair geometry is tetrahedral.
Structure Determination by
VSEPR
The MOLECULAR GEOMETRY — the positions of the atoms — is PYRAMIDAL.
![Page 42: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/42.jpg)
42
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRWater, H2O
1. Draw electron dot structure
The electron pair geometry is TETRAHEDRAL.
2. Count BP’s and LP’s = 4
3. The 4 electron pairs are at the corners of a tetrahedron.
![Page 43: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/43.jpg)
43
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRWater, H2O
The electron pair geometry is TETRAHEDRAL
The molecular geometry is BENT.
![Page 44: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/44.jpg)
44
© 2006 Brooks/Cole - Thomson
Geometries for Four Electron Pairs
Figure 9.9
![Page 45: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/45.jpg)
45
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRFormaldehyde, CH2O
1. Draw electron dot structure
The electron pair geometry is PLANAR TRIGONAL with 120o bond angles.
••
C HH
O••
••
CHH
O••
2. Count BP’s and LP’s at C3. There are 3 electron “lumps” around C at the corners of a planar triangle.
![Page 46: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/46.jpg)
46
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRFormaldehyde, CH2O
The electron pair geometry is PLANAR TRIGONAL
The molecular geometry is also planar trigonal.
![Page 47: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/47.jpg)
47
© 2006 Brooks/Cole - Thomson
H-C-H = 109o
C-O-H = 109o
In both cases the atom is surrounded by 4 electron pairs.
Structure Determination by
VSEPRH
H
••
••H—C—O—H
109˚ 109˚
Methanol, CH3OH
Define H-C-H and C-O-H bond angles
![Page 48: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/48.jpg)
48
© 2006 Brooks/Cole - Thomson
Structure Determination by
VSEPRAcetonitrile, CH3CN
••
H
H
H—C—C N
180˚109˚H-C-H = 109o C-C-N = 180o
One C is surrounded by 4 electron “lumps” and the other by 2 “lumps”
Define unique bond angles
![Page 49: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/49.jpg)
49
© 2006 Brooks/Cole - Thomson
Phenylalanine, an amino acid
![Page 50: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/50.jpg)
50
© 2006 Brooks/Cole - Thomson
Phenylalanine
![Page 51: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/51.jpg)
51
© 2006 Brooks/Cole - Thomson
Structures with Central Atoms with More Than or Less Than 4 Electron Pairs
Often occurs with Group 3A elements and with those of 3rd period and higher.
![Page 52: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/52.jpg)
52
© 2006 Brooks/Cole - Thomson
Boron Compounds
Consider boron trifluoride, BF3
Geometry described as
planar trigonal
The B atom is surrounded by only 3 electron pairs.
Bond angles are 120o
![Page 53: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/53.jpg)
53
© 2006 Brooks/Cole - Thomson
5 electron pairs
Compounds with 5 or 6 Pairs Around the Central Atom
![Page 54: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/54.jpg)
54
© 2006 Brooks/Cole - Thomson
Molecular Geometries for Five Electron
PairsFigure 9.11
All based on trigonal bipyramid
![Page 55: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/55.jpg)
55
© 2006 Brooks/Cole - Thomson
• Number of valence electrons = 34
• Central atom = S• Dot structure
Sulfur Tetrafluoride, SF4
Electron pair geometry--> trigonal bipyramid (because there are 5 pairs around the S)
![Page 56: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/56.jpg)
56
© 2006 Brooks/Cole - Thomson
Lone pair is in the equator because it requires more room.
Sulfur Tetrafluoride, SF4
![Page 57: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/57.jpg)
57
© 2006 Brooks/Cole - Thomson
Molecular Geometries
for Six Electron
PairsFigure 9.14
All are based on the 8-sided octahedron
![Page 58: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/58.jpg)
58
© 2006 Brooks/Cole - Thomson
6 electron pairs
Compounds with 5 or 6 Pairs Around the Central Atom
![Page 59: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/59.jpg)
59
© 2006 Brooks/Cole - Thomson
Bond Properties• What is the effect of bonding and structure on
molecular properties?
Free rotation around C–C single bond
No rotation around C=C double bond
![Page 60: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/60.jpg)
60
© 2006 Brooks/Cole - Thomson
Bond Order # of bonds between a pair of atoms
Double bondSingle bond
Triple bond
Acrylonitrile
![Page 61: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/61.jpg)
61
© 2006 Brooks/Cole - Thomson
Bond OrderFractional bond orders occur in molecules with resonance
structures.
Consider NO2-
The N—O bond order = 1.5
![Page 62: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/62.jpg)
62
© 2006 Brooks/Cole - Thomson
Bond OrderBond order is proportional to two important bond
properties:
(a) bond strength(b) bond length
745 kJ
414 kJ
110 pm
123 pm
![Page 63: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/63.jpg)
63
© 2006 Brooks/Cole - Thomson
Bond LengthBond length depends on
size of bonded atoms.
H—F
H—Cl
H—I
Bond distances measured in Angstrom units where 1 A = 10-2 pm.
![Page 64: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/64.jpg)
64
© 2006 Brooks/Cole - Thomson
Bond length depends on bond order.
Bond distances measured in Angstrom units where 1 A = 10-2 pm.
Bond Length
![Page 65: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/65.jpg)
65
© 2006 Brooks/Cole - Thomson
• —measured by the energy req’d to break a bond. See Table 9.10.
• BOND STRENGTH (kJ/mol) H—H 436 C—C 346 C=C 602 CC 835 NN 945
The GREATER the number of bonds (bond order) the HIGHER the bond strength and the SHORTER the bond.
Bond Strength
![Page 66: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/66.jpg)
66
© 2006 Brooks/Cole - Thomson
Bond Order Length Strength
HO—OH
O=O
1 142 pm 210 kJ/mol
2 121 498
1.5 128 ?
Bond Strength
![Page 67: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/67.jpg)
67
© 2006 Brooks/Cole - Thomson
Molecular Polarity
Why do ionic compounds dissolve in water?
WaterBoiling point =
100 ˚C
MethaneBoiling point
= -161 ˚C
Why do water and methane differ so much in their
boiling points?
![Page 68: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/68.jpg)
68
© 2006 Brooks/Cole - Thomson
Bond Polarity
HCl is POLAR because it has a positive end and a negative end.
Cl has a greater share in bonding electrons than does H.
Cl has slight negative charge (-d) and H has slight positive charge (+ d)
![Page 69: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/69.jpg)
69
© 2006 Brooks/Cole - Thomson
Bond Polarity
• Three molecules with polar, covalent bonds.
• Each bond has one atom with a slight negative charge (-d) and and another with a slight positive charge (+ d)
![Page 70: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/70.jpg)
70
© 2006 Brooks/Cole - Thomson
This model, calc’d using CAChe
software for molecular
calculations, shows that H is +
(red) and Cl is - (yellow). Calc’d
charge is + or - 0.20.
Bond Polarity
![Page 71: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/71.jpg)
71
© 2006 Brooks/Cole - Thomson
Due to the bond polarity, the H—Cl bond energy is GREATER than expected for a “pure” covalent bond.
BOND ENERGY“pure” bond339 kJ/mol calc’dreal bond 432 kJ/mol measured
Difference = 92 kJ. This difference is proportional to the difference in
ELECTRONEGATIVITY, .
Bond Polarity
![Page 72: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/72.jpg)
72
© 2006 Brooks/Cole - Thomson
Electronegativity, is a measure of the ability of an atom in a
molecule to attract electrons to itself.
Concept proposed by Linus Pauling 1901-1994
![Page 73: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/73.jpg)
73
© 2006 Brooks/Cole - Thomson
Linus Pauling, 1901-1994
The only person to receive two unshared Nobel prizes (for Peace and Chemistry).
Chemistry areas: bonding, electronegativity, protein structure
![Page 74: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/74.jpg)
74
© 2006 Brooks/Cole - Thomson
ElectronegativityFigure 9.14
![Page 75: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/75.jpg)
75
© 2006 Brooks/Cole - Thomson
• F has maximum .• Atom with lowest is the center atom in
most molecules.• Relative values of determine BOND
POLARITY (and point of attack on a molecule).
Electronegativity,
See Figure 9.14
![Page 76: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/76.jpg)
76
© 2006 Brooks/Cole - Thomson
Bond PolarityWhich bond is more polar (or DIPOLAR)? O—H O—F 3.5 - 2.1 3.5 - 4.0 1.4 0.5 OH is more polar than OF
and polarity is “reversed.”
![Page 77: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/77.jpg)
77
© 2006 Brooks/Cole - Thomson
Molecular PolarityMolecules—such as HI and H2O—
can be POLAR (or dipolar).
They have a DIPOLE MOMENT. The polar HCl molecule will turn to align with an electric field.
![Page 78: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/78.jpg)
78
© 2006 Brooks/Cole - Thomson
Molecular PolarityThe magnitude of the dipole is
given in Debye units.
Named for Peter Debye
(1884 - 1966). Rec’d 1936
Nobel prize for work on x-
ray diffraction and dipole
moments.
![Page 79: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/79.jpg)
79
© 2006 Brooks/Cole - Thomson
Dipole Moments
Why are some molecules polar but others are not?
![Page 80: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/80.jpg)
80
© 2006 Brooks/Cole - Thomson
Molecular PolarityMolecules will be polar ifa)bonds are polar ANDb) the molecule is NOT “symmetric”
All above are NOT polar
![Page 81: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/81.jpg)
81
© 2006 Brooks/Cole - Thomson
Polar or Nonpolar?Compare CO2 and H2O. Which one is polar?
![Page 82: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/82.jpg)
82
© 2006 Brooks/Cole - Thomson
Carbon Dioxide
• CO2 is NOT polar even though the CO bonds are polar.
• CO2 is symmetrical.
+1.5 -0.75-0.75
Positive C atom is reason CO2 and H2O react to give H2CO3
![Page 83: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/83.jpg)
83
© 2006 Brooks/Cole - Thomson
Polar or Nonpolar?• Consider AB3 molecules: BF3, Cl2CO, and NH3.
![Page 84: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/84.jpg)
84
© 2006 Brooks/Cole - Thomson
Molecular Polarity, BF3
B atom is positive and F atoms are negative.
B—F bonds in BF3 are polar.
But molecule is symmetrical and NOT polar
![Page 85: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/85.jpg)
85
© 2006 Brooks/Cole - Thomson
Molecular Polarity, HBF2
B atom is positive but H & F atoms are negative.
B—F and B—H bonds in HBF2 are polar. But molecule is NOT symmetrical and is polar.
![Page 86: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/86.jpg)
86
© 2006 Brooks/Cole - Thomson
Is Methane, CH4, Polar?
Methane is symmetrical and is NOT polar.
![Page 87: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/87.jpg)
87
© 2006 Brooks/Cole - Thomson
Is CH3F Polar?
C—F bond is very polar. Molecule is not symmetrical and so is polar.
![Page 88: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/88.jpg)
88
© 2006 Brooks/Cole - Thomson
CH4 … CCl4
Polar or Not?
• Only CH4 and CCl4 are NOT polar. These are the only two molecules that are “symmetrical.”
![Page 89: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/89.jpg)
89
© 2006 Brooks/Cole - Thomson
Substituted Ethylene
• C—F bonds are MUCH more polar than C—H bonds.
• Because both C—F bonds are on same side of molecule, molecule is POLAR.
![Page 90: 1 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 9 Bonding and Molecular](https://reader038.vdocuments.us/reader038/viewer/2022103015/551c240e550346ad4f8b5cc8/html5/thumbnails/90.jpg)
90
© 2006 Brooks/Cole - Thomson
Substituted Ethylene
• C—F bonds are MUCH more polar than C—H bonds.
• Because both C—F bonds are on opposing ends of molecule, molecule is NOT POLAR.