molecular shapes - chemgod.com 216/2 - 3d molecular models.pdf · molecular shapes putting it all...
TRANSCRIPT
Slide 1
Molecular ShapesPutting it all together
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Slide 2 SeO2
One more example:
What’s the Lewis Dot Structure for SeO2?
1st question:
What’s the total # of valence electrons?
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Slide 3
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Slide 4 Dot structure for SeO2
SeO2
18 total valence electrons.
Next question:
What’s the central atom?
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Slide 5 Dot structure for SeO2
O — Se — O
Now?
Fill the octets
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Slide 6 Dot structure for SeO2
.. .. ..
:O — Se — O:
¨ ¨ ¨
Once we’ve filled the octets, what do we do?
Check the total # of valence electrons
20 total electrons – too many!
So, what do we do?
Make a bond!
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Slide 7 Dot structure for SeO2
..:O = Se — O:
¨ ¨ ¨
Are we done?
Check the formal charges.FC(left O) = 6 – 2 – 4 = 0FC(Se) = 6 – 3 – 2 = 1FC(right O) = 6 – 1 – 6 = -1 Acceptable. Are we done yet?
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Slide 8
RESONANCE
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Slide 9 Dot structure for SeO2
..
:O = Se — O:
¨ ¨ ¨
..
:O — Se = O:
¨ ¨ ¨
Resonance is always good!
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Slide 10 SO2
One final example:
What’s the Lewis Dot Structure for SO2?
1st question:
What’s the total # of valence electrons?
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Slide 11
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Slide 12 Dot structure for SO2
SO2
18 total valence electrons.
Next question:
What’s the central atom?
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Slide 13 Dot structure for SO2
O — S— O
Now?
Fill the octets
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Slide 14 Dot structure for SO2
.. .. ..
:O — S — O:
¨ ¨ ¨
Once we’ve filled the octets, what do we do?
Check the total # of valence electrons
20 total electrons – too many!
So, what do we do?
Make a bond!
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Slide 15 Dot structure for SO2
..:O = S — O:
¨ ¨ ¨
Are we done?
Check the formal charges.FC(left O) = 6 – 2 – 4 = 0FC(S) = 6 – 3 – 2 = 1FC(right O) = 6 – 1 – 6 = -1 Acceptable. Is it the best?
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Slide 16 Dot structure for SO2
:O = S = O:¨ ¨ ¨
S can have an expanded octet, we can make a bond out of 2 electrons from O without eliminating any S electrons?
Check the formal charges.FC(O) = 6 – 2 – 4 = 0FC(S) = 6 – 4 – 2 = 0EVEN BETTER THAN THE PREVIOUS STRUCTURE!
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Slide 17
Once you have a Lewis Structure, then you can determine the 3-D Molecular structure – AND ITS EASY!!!!
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Slide 18 3-D Molecular Structures
What holds molecules together?
ELECTRONS
What is on the outside of all molecules?
ELECTRONS
What do we know about electrons?
THEY HATE EACH OTHER
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Slide 19 Joe hates Jane
Joe and Jane hate each other (the reasons are unclear, but Jane never got a phone call much less the jewelry she thought she deserved! )
Joe and Jane both go to Bob’s party. If I’m in the kitchen, where’s Jane?
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Slide 20
ANYWHERE BUT THE KITCHEN!
(unless she wants to make out with my brother right in front of me just to try and p*&& me off!)
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Slide 21 3-D Molecular Models
One rule – VSEPR
Valence Shell Electron Pair Repulsion
Electrons hate each other, they stay as far away from each other as possible!!!
One corollary to the rule: non-bonding pairs hate each other more than bonds.
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Slide 22
The rest is all geometry! And only the geometry of central atoms matters.
Consider CO2 – what’s the LDS?
.. ..
:O = C = O :
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Slide 23
.. ..
:O = C = O :
Look at carbon, how many electron groups does it have around it?
2 – 2 sets of double bonds (all bonds, whether single, double, or triple count as a single group)
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Slide 24
.. ..
:O = C = O :
2 electron groups that hate each other (like Joe and Jane) –what’s the farthest apart they can get?
Completely opposite sides of the molecule!
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Slide 25 Move either C-O bond and it gets closer to the other one!
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Slide 26 Space-filling model
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Slide 27 What about CH2O
Total Valence electrons?
4 + 2*1 + 6 = 12
Central atom?
Carbon
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Slide 28 Connect the atoms and fill octets
..
:O:
|
H— C — H
¨
Total electrons – 14 electrons
What’s the solution?
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Slide 29 LDS
:O:
| |
H— C — H
Total electrons – 12 electrons
Formal charges are all ZERO
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Slide 30 3-D Geometry
:O:| |
H— C — H
Joe, Jane, and Amanda all hate each other (boy was that a bad night of Tequila and pills! ) If they all end up at the same bar, what’s the farthest apart they can get?
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Slide 31 3-D Geometry – Trigonal planar
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Slide 32 Not all bonds are the same
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Slide 33 Methane – CH4
H|
H — C —H|
H
4 electron groups around the central atom.Joe and Jane and Amanda and Brad all hate each other
ever since that night with the Tequila and Joe and Jane broke up and Brad and Amanda broke up and Joe woke up with Brad and Amanda woke up with Jane… If they are all in the cafeteria, how far apart can they get?
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Slide 34 Tetrahedral Geometry, a little harder to see…
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Slide 35 It’s basically a pyramid
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Slide 36 You don’t need to predict it…
…it’s automatic!
2 electron groups – linear
3 electron groups – trigonal planar
4 electron groups – tetrahedral
Geometry demands it!
And, since 4 electron groups is an octet, that’s the whole story, right?
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Slide 37 Expanded Octets
For S, P that have expanded octets, you can have more complicated geometries.
BUT, they are also automatic based on the number of electron groups that hate each other.
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Slide 38 PCl5
Another one of my favorite molecules!
Cl Cl
Cl — P — Cl|Cl
Joe and Amanda and Jane and Brad and Laura…never mind, you know the drill!
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Slide 39 Trigonal Bipyramidal
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Slide 40 Two pyramids, base-to-base
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Slide 41 SF6 – love this molecule also!
F F
F — S — F
F F
6 electron groups that hate each other!
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Slide 42 Octahedral Geometry
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Slide 43 Two 4-sided pyramids, base-to-base
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Slide 44 Geometry is 3000 years old!
2 electron groups – linear
3 electron groups – trigonal planar
4 electron groups – tetrahedral
5 electron groups – trigonal bipyramidal
6 electron groups – octahedral
And the angles are “sort-of” predictable
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Slide 45 Geometry is 3000 years old!
2 electron groups – linear - 180º3 electron groups – trigonal planar - 120º
4 electron groups – tetrahedral – 109.5º
5 electron groups – trigonal bipyramidal - 90º, 120º
6 electron groups – octahedral - 90º
This ASSUMES every position is identical – the real world has nuances
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Slide 46 Lone pairs vs. bonding pairs
NH3 vs. CH4
H
.. |
H — N — H H — C —H
| |
H H
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Slide 47
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Slide 48 Water
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Slide 49 MOLECULAR geometry vs. ELECTRON geometryThe molecular geometry is just the geometry of the bonds,
ignoring non-bonding electrons.
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Slide 50 Ammonia
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Slide 51 Water
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Slide 52
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Slide 53 Expanded octets
5
5
5
6
6
6
5
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Slide 54 Clicker question
What is the ELECTRON geometry of NO2-?
A. Tetrahedral
B. Trigonal planar
C. Bent
D. Linear
E. Octahedral
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Slide 55 What is the bond angle in NO2
-?
A. 90 degrees
B. 120 degrees
C. 117 degrees
D. 107 degrees
E. 109.5 degrees
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Slide 56 Clicker question
What is the molecular geometry of NO2-?
A. Tetrahedral
B. Trigonal planar
C. Bent
D. Linear
E. Octahedral
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Slide 57 Polarity of Molecules
• in order for a molecule to be polar it must1) have polar bonds
• electronegativity difference - theory
• bond dipole moments - measured
2) have an unsymmetrical shape• vector addition
• polarity affects the intermolecular forces of attraction• therefore boiling points and solubilities
• like dissolves like
• nonbonding pairs affect molecular polarity, strong pull in its direction
Tro, Chemistry: A Molecular
Approach 57
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Slide 58 What holds molecules together?
Bonds
Bonds are made up of?
Electrons
How do the electrons hold atoms together?
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Slide 59 Two ways:
Ionic Bonds – attraction between ions of opposite charges
Na+ Cl-
Covalent Bonds – sharing of electrons between adjacent atoms
PF3
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Slide 60 Are they really different?
Let’s share a pie!
Which pie are we actually sharing?
Mine YoursYours Mine
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Slide 61
Sharing doesn’t have to be equal!
Mine
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Slide 62 Ionic and covalent are part of a
continuum
Ionic Covalent
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Slide 63 Two extremes
Mine Yours
Ours
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Slide 64 Something in the middle
Mine YoursYours Mine
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Slide 65 Ionic and covalent are part of a
continuum
Ionic Uneven sharing Equal sharing
Non-polarPolar
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Slide 66 So, consider a bond, any bond:
Cl – Cl
Which case is this?
Equal sharing!
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Slide 67 So, consider a bond, any bond:
H-Cl
Which case is this?
Unequal sharing! How do you know?
They are on opposite sides of the Periodic table!
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Slide 68
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Slide 69 A metal + a non-metal =
An ionic compound!
Non-metals love electrons, metals don’t!
There is a periodic trend for “electron love”: electronegativity or electron affinity.
Electronegativity increases to the right and going up (F is most electronegative, Fr is least)
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Slide 70
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Slide 71 Electronegativity determines polarity
The polarity of a bond is determined by the difference in electronegativity between the atoms at either end of the bond.
E.N. = Larger E.N. – smaller E.N.
If E.N. < 0.4, its considered non-polar
If 0.4 < E.N. < 2.0, its considered polar
If E.N. > 2.0, its considered ionic
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Slide 72
Cl – Cl
E.N. = 3.0 – 3.0 = 0Non-polar
H-Cl
E.N. = 3.0 – 2.1 = 0.9Polar
NaCl E.N. = 3.0 – 0.9 = 2.1Ionic
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Slide 73 Polarity is represented as an arrow……pointing toward the more negative atom.
Cl – Cl
H-Cl
NaCl
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Slide 74 Molecule Polarity
Tro, Chemistry: A Molecular
Approach 74
The H-Cl bond is polar. The bonding electrons are
pulled toward the Cl end of the molecule. The net result
is a polar molecule.
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Slide 75 H2O vs. CO2
O = C = O
What can we say about the bonds?
E.N. = 3.5 – 2.5 = 1.0
Polar
..
H – O – H
What can we say about the bonds?
E.N. = 3.5 – 2.1 = 1.4
Polar
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Slide 76 Does that make sense?
What do you know about water?
Yup, it’s a polar solvent.
What about CO2? Would you expect it to be polar?
Would it surprise you to learn that CO2 is NONPOLAR?!?!?!?
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Slide 77 It’s all in the geometry.
CO2 has two polar bonds, but…
the polarity is equal and oppositely directed, so it cancels!
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Slide 78 H2O
Water also has two equally polar bonds, but they aren’t pointing in opposite directions.
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Slide 79 H2O
Polarity is a “vector”, it has size and direction. You can’t separate the two. Think of it as travel directions.
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Slide 80
If I leave my house and go 1 mile North and then 1 mile South, where am I?
1 mile North1 mile South
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Slide 81
If I leave my house and go 1 mile North, and then 1 mile West, where am I?
1 mile North
1 mile West
1.414 mi NW
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Slide 82 H2O
A polarity vector is just the direction that a proton would go (toward the negative), and the length of the vector is its magnitude.
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Slide 83 H2O
The polarity of the molecule is distinct from the polarity of the bonds in the molecule.
Non-polar bonds = Non-polar molecule
Polar bonds…depends on the geometry!
NetDipole
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Slide 84 Vector Addition
Tro, Chemistry: A Molecular
Approach 84
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Slide 85
Tro, Chemistry: A Molecular
Approach 85
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Slide 86 Molecule Polarity
Tro, Chemistry: A Molecular
Approach 86
The O-C bond is polar. The bonding electrons are
pulled equally toward both O ends of the molecule. The
net result is a nonpolar molecule.
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Slide 87 Molecule Polarity
Tro, Chemistry: A Molecular
Approach 87
The H-O bond is polar. The both sets of bonding
electrons are pulled toward the O end of the
molecule. The net result is a polar molecule.
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Slide 88 Molecule Polarity
Tro, Chemistry: A Molecular
Approach 88
The H-N bond is polar. All the sets of bonding
electrons are pulled toward the N end of the
molecule. The net result is a polar molecule.
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Slide 89
N=3.0, H = 2.1
EN=0.9 (polar)
They don’t cancel, all 3 are pointing up and nothing is pointing down!
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Slide 90 Clicker
Is CCl4…
A. Polar
B. Non-polar
C. Ionic
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Slide 91 Clicker
Is CH2Cl2…
A. Slightly Polar
B. Really polar
C. Non-polar
D. I hate Christmas
E. I hate you!
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Slide 92 Lewis structure
The bonds are…
Polar – C=2.5, Cl=3.0 EN=0.5 (weakly polar)
The molecular geometry is…
Tetrahedral
C Cl
Cl
Cl
Cl
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Slide 93 Do the polarities cancel?
A 3-D model helps…
CCl
Cl
Cl
Cl
CCl
Cl
C
Doesn’t completely cancel because they aren’t pointing directly opposite.
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Slide 94 Clicker
Is HCN…
A. Polar
B. Non-polar
C. Ionic
D. I hate Hanukkah
E. I hate Kwanzaa
F. I hate you.
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Slide 95
H = 2.1C = 2.5N = 3.0
C-H is nonpolar (EN=0.4)C-N is polar (EN=0.5)
Molecule is weakly polar.
C N:H
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Slide 96 A very brief review of geometry
We need:
1. Electron configuration – to get the number of valence electrons
2. Lewis structure – to determine “where” the valence electrons are.
3. 3-D Molecular structure – VSEPR determines shape of the molecules by determining position of electron groups
4. Polarity – unequal sharing of electron density creates polar bonds and (maybe) polar molecules.
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Slide 97 Let’s try NOCl – polar or non-polar?
First we need the Lewis structure
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Slide 98
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Slide 99 Let’s try NOCl – polar or non-polar
First we need the Lewis structure
N has 5 valence electrons (2s22p3)
O has 6 valence electrons (2s22p4)
Cl has 7 valence electrons (3s23p5)
That’s a total of 18 valence electrons!
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Slide 100 What’s the most likely central atom?
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Slide 101
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Slide 102 Leftmost or down most.
N is the farthest to the left of the periodic table. N is the most likely central atom.
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Slide 103 Stick everything to N and fill octets.
Check the number of valence electrons used
20! That’s not 18!
N ClO
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Slide 104 How do I get rid of electrons?
Make a double bond!
But where…?
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Slide 105 When in doubt, try them all!
So, which one is it? Or is it resonance?!?!?
N ClO
N ClO
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Slide 106 Let formal charges sort them out!
6-1-6=-1 5-3-2=0 7-2-4=+1
N ClO
N ClO
6-2-4=0 5-3-2=0 7-1-6=0
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Slide 107 We have a winner!
N ClO
Is it polar or non-polar?
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Slide 108 We need to consider the bonds and
the shape.
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Slide 109 First…the bonds.
Tro, Chemistry: A Molecular
Approach
109
O N Cl ••••
••
••
••••EN
O = 3.5
N = 3.0
Cl = 3.0
Calculate the electronegative difference for EACH
bond
N=O ΔEN = 3.5-3.0 = 0.5 (barely polar)
N-Cl ΔEN = 3.0-3.0 = 0.0 (not polar)
So I have a polar bond and nothing to cancel it, so
the molecule must be weakly polar. I really don’t
even need to consider shape, but let’s look anyway!
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Slide 110 3 Electron groups around the central atom
Tro, Chemistry: A Molecular
Approach
110
polar
1) polar bonds, N-O
2) asymmetrical shape
O N Cl ••••
••
••
••••Electron geometry – Trigonal planar
Molecular geometry - bent
Cl
N
O
3.0
3.0
3.5
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Slide 111 Clicker question
What is the O-N-Cl bond angle?
A.180 degrees
B.123 degrees
C.120 degrees
D.117 degrees
E.90 degrees
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Slide 112 Let’s try one more
SO3 – polar or non-polar?
First we need the Lewis structure
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Slide 113
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Slide 114 Let’s try SO3 – polar or non-polar
First we need the Lewis structure
S has 6 valence electrons (3s23p4)
O has 6 valence electrons (2s22p4)
That’s a total of 24 valence electrons!
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Slide 115 What’s the most likely central atom?
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Slide 116
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Slide 117 Leftmost or down most.
S and O are equally to the left of the periodic table. S is below O. S is the most likely central atom.
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Slide 118 Stick everything to S and fill octets.
Check the number of valence electrons used
26! That’s not 24!
S OO
O
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Slide 119 How do I get rid of electrons?
Make a double bond!
But where…?
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Slide 120 When in doubt, try them all!
So, which one is it? Or is it resonance?!?!?
S OO
O
S OO
O
S OO
O
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Slide 121 Check the formal charges
All equivalent S: 6-4-0=+2
O: 6-2-4=0 O:6-2-6=-1
S OO
O
S OO
O
S OO
O
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Slide 122 It’s resonance!
S OO
O
S OO
O
S OO
O
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Slide 123 We need to consider the bonds and
the shape.
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Slide 124
First the bonds:
Tro, Chemistry: A Molecular
Approach
124
O S
O
O
••
••
••
••
••••
••
••EN
O = 3.5
S = 2.5
ΔEN=3.5-2.5=1.0 (all 3 bonds are polar!)
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Slide 125 But let’s check the geometry!
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Slide 126 Ah…symmetry!
Tro, Chemistry: A Molecular
Approach
126
nonpolar
1) polar bonds, all S-O
2) symmetrical shape
O S
O
O
••
••
••
••
••••
••
••
Trigonal
Planar
O
O
OS
3.5
3.5 3.5
2.5
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Slide 127 This is the starting point…
Polarity influences how molecules interact with each
other.
Molecular interactions influence physical properties of
materials.
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Slide 128 Molecular Polarity Affects Solubility in Water
• polar molecules are attracted to other polar molecules
• since water is a polar molecule, other polar molecules dissolve well in water• and ionic compounds as well
• some molecules have both polar and nonpolar parts
Tro, Chemistry: A Molecular
Approach 128
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Slide 129 A Soap MoleculeSodium Stearate
Tro, Chemistry: A Molecular
Approach 129
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Slide 130 Problems with Lewis Theory• Lewis theory gives good first approximations of the bond angles in
molecules, but usually cannot be used to get the actual angle
• Lewis theory cannot write one correct structure for many molecules where resonance is important
• Lewis theory often does not predict the correct magnetic behavior of molecules• e.g., O2 is paramagnetic, though the Lewis structure predicts it is
diamagnetic
Tro, Chemistry: A Molecular
Approach 130
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Slide 131 Valence Bond Theory
• Linus Pauling and others applied the principles of quantum mechanics to molecules
• they reasoned that bonds between atoms would arise when the orbitals on those atoms interacted to make a bond
• the kind of interaction depends on whether the orbitals align along the axis between the nuclei, or outside the axis
Tro, Chemistry: A Molecular
Approach 131
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Slide 132 Orbital Interaction
• as two atoms approached, the partially filled or empty valence atomic orbitals on the atoms would interact to form molecular orbitals
• the molecular orbitals would be more stable than the separate atomic orbitals because they would contain paired electrons shared by both atoms• the interaction energy between atomic orbitals is negative when the
interacting atomic orbitals contain a total of 2 electrons
Tro, Chemistry: A Molecular
Approach 132
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Slide 133 Orbital Diagram for the Formation of H2S
Tro, Chemistry: A Molecular
Approach 133
+
↑
H
1s ↑↓ H-S bond
↑
H
1s
S↑ ↑ ↑↓↑↓
3s 3p
↑↓ H-S bond
Predicts Bond Angle = 90
Actual Bond Angle = 92
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Slide 134 Valence Bond Theory - Hybridization• one of the issues that arose was that the number of
partially filled or empty atomic orbital did not predict the number of bonds or orientation of bonds • C = 2s22px
12py12pz
0 would predict 2 or 3 bonds that are 90° apart, rather than 4 bonds that are 109.5° apart
• to adjust for these inconsistencies, it was postulated that the valence atomic orbitals could hybridize before bonding took place• one hybridization of C is to mix all the 2s and 2p orbitals to get 4 orbitals
that point at the corners of a tetrahedron
Tro, Chemistry: A Molecular
Approach 134
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Slide 135 Unhybridized C Orbitals Predict the Wrong Bonding & Geometry
Tro, Chemistry: A Molecular
Approach 135
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Slide 136 Valence Bond TheoryMain Concepts
1. the valence electrons in an atom reside in the quantum mechanical atomic orbitals or hybrid orbitals
2. a chemical bond results when these atomic orbitals overlap and there is a total of 2 electrons in the new molecular orbital
a) the electrons must be spin paired
3. the shape of the molecule is determined by the geometry of the overlapping orbitals
Tro, Chemistry: A Molecular
Approach 136
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Slide 137 Hybridization
• some atoms hybridize their orbitals to maximize bonding
• hybridizing is mixing different types of orbitals to make a new set of degenerate orbitals
• sp, sp2, sp3, sp3d, sp3d2
• more bonds = more full orbitals = more stability
• better explain observed shapes of molecules
• same type of atom can have different hybridization depending on the compound
• C = sp, sp2, sp3
Tro, Chemistry: A Molecular
Approach 137
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Slide 138 How many hybrid orbitals does water need?A. 1
B. 2
C. 3
D. 4
E. 6
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Slide 139 Hybrid Orbitals• H cannot hybridize!!
• the number of standard atomic orbitals combined = the number of hybrid orbitals formed
• the number and type of standard atomic orbitals combined determines the shape of the hybrid orbitals
• the particular kind of hybridization that occurs is the one that yields the lowest overall energy for the molecule
• in other words, you have to know the structure of the molecule beforehand in order to predict the hybridization
Tro, Chemistry: A Molecular
Approach 139
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Slide 140 Orbital Diagrams with Hybridization• place electrons into hybrid and unhybridized valence orbitals
as if all the orbitals have equal energy
• when bonding, s bonds form between hybrid orbitals and pbonds form between unhybridized orbitals that are parallel
Tro, Chemistry: A Molecular
Approach 140
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Slide 141 Carbon Hybridizations
Tro, Chemistry: A Molecular
Approach 141
Unhybridized
2s 2p
sp hybridized
2sp
sp2 hybridized
2p
sp3 hybridized
2p
2sp2
2sp3
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Slide 142
sp3 Hybridization• atom with 4 areas of electrons
• tetrahedral geometry
• 109.5° angles between hybrid orbitals
• atom uses hybrid orbitals for all bonds and lone pairs
Tro, Chemistry: A Molecular
Approach 142
H C N H
H
H H
s
•• sp3
s
sp3
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Slide 143 sp3 Hybridization of C
Tro, Chemistry: A Molecular
Approach 143
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Slide 144
Tro, Chemistry: A Molecular
Approach 144
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Slide 145 How many electron groups in CO2A. 6
B. 5
C. 4
D. 3
E. 2
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Slide 146 sp3 Hybridized AtomsOrbital Diagrams
Tro, Chemistry: A Molecular
Approach 146
Unhybridized atom
2s 2p
sp3 hybridized atom
2sp3
C
2s 2p
2sp3
N
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Slide 147 Methane Formation with sp3 C
Tro, Chemistry: A Molecular
Approach 147
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Slide 148 Ammonia Formation with sp3
N
Tro, Chemistry: A Molecular
Approach 148
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Slide 149 CH3NH2 Orbital Diagram
Tro, Chemistry: A Molecular
Approach 149
sp3 C sp3 N
1s H
s
sss s s
1s H 1s H 1s H 1s H
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Slide 150 Practice - Draw the Orbital Diagram for the sp3 Hybridization of Each Atom
Tro, Chemistry: A Molecular
Approach 150
Unhybridized atom
3s 3p
Cl
2s 2p
O
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Slide 151 Practice - Draw the Orbital Diagram for the sp3 Hybridization of Each Atom
Tro, Chemistry: A Molecular
Approach 151
Unhybridized atom
3s 3p
Cl
2s 2p
O
sp3 hybridized atom
3sp3
2sp3
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Slide 152 Types of Bonds
• a sigma (s) bond results when the bonding atomic orbitals point along the axis connecting the two bonding nuclei• either standard atomic orbitals or hybrids
• s-to-s, p-to-p, hybrid-to-hybrid, s-to-hybrid, etc.
• a pi (p) bond results when the bonding atomic orbitals are parallel to each other and perpendicular to the axis connecting the two bonding nuclei• between unhybridized parallel p orbitals
• the interaction between parallel orbitals is not as strong as between orbitals that point at each other; therefore s bonds are stronger than p bonds
Tro, Chemistry: A Molecular
Approach 152
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Slide 153
Tro, Chemistry: A Molecular
Approach 153
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Slide 154
Tro, Chemistry: A Molecular
Approach 154
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Slide 155 Bond Rotation
• because orbitals that form the s bond point along the internuclear axis, rotation around that bond does not require breaking the interaction between the orbitals
• but the orbitals that form the p bond interact above and below the internuclear axis, so rotation around the axis requires the breaking of the interaction between the orbitals
Tro, Chemistry: A Molecular
Approach 155
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Slide 156
Tro, Chemistry: A Molecular
Approach 156
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Slide 157
Tro, Chemistry: A Molecular
Approach 157
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Slide 158
sp2
• atom with 3 areas of electrons
• trigonal planar system
• C = trigonal planar
• N = trigonal bent
• O = “linear”
• 120° bond angles
• flat
• atom uses hybrid orbitals for s bonds and lone pairs, uses nonhybridized p orbital for p bond
Tro, Chemistry: A Molecular
Approach 158
H C O H
O ••
sp2s ••
••
••sp2
sp3 s
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Slide 159
Tro, Chemistry: A Molecular
Approach 159
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Slide 160
Tro, Chemistry: A Molecular
Approach 160
+
sp2 sp2
p
s
Hybrid orbitals overlap to form s bond
Unhybridized p orbitals overlap to form p bond
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Slide 161
Tro, Chemistry: A Molecular
Approach 161
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Slide 162 sp2 Hybridized AtomsOrbital Diagrams
Tro, Chemistry: A Molecular
Approach 162
Unhybridized atom
2s 2p
sp2 hybridized atom
2sp2
2p
C
3 s
1 p
2s 2p
2sp2
2p
N
2 s
1 p
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Slide 163 CH2NH Orbital Diagram
Tro, Chemistry: A Molecular
Approach 163
sp2 C
sp2 N
1s H
s
ss s
1s H 1s H
p C p N
p
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Slide 164 Practice - Draw the Orbital Diagram for the sp2 Hybridization of Each Atom. How many sand pbonds would you expect each to form?
Tro, Chemistry: A Molecular
Approach 164
Unhybridized atom
2s 2p
B
2s 2p
O
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Slide 165 Practice - Draw the Orbital Diagram for the sp2 Hybridization of Each Atom. How many sand pbonds would you expect each to form?
Tro, Chemistry: A Molecular
Approach 165
Unhybridized atom
2s 2p
B
3 s
0 p
2s 2p
O
1 s
1 p
sp2 hybridized atom
2sp2
2p
2sp2
2p
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Slide 166
sp• atom with 2 areas of electrons
• linear shape
• 180° bond angle
• atom uses hybrid orbitals for s bonds or lone pairs, uses nonhybridized p orbitals for p bonds
Tro, Chemistry: A Molecular
Approach 166
H C N
sp sps
p
p
s
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Slide 167
Tro, Chemistry: A Molecular
Approach 167
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Slide 168
Tro, Chemistry: A Molecular
Approach 168
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Slide 169 spHybridized AtomsOrbital Diagrams
Tro, Chemistry: A Molecular
Approach 169
Unhybridized atom
2s 2p
sp hybridized atom
2sp
2p
C
2s
2p
2s 2p
2sp
2p
N
1s
2p
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Slide 170 HCN Orbital Diagram
Tro, Chemistry: A Molecular
Approach 170
sp C
sp N
1s H
s
s
p C p N
2p
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Slide 171 sp3d
• atom with 5 areas of electrons around it• trigonal bipyramid shape
• See-Saw, T-Shape, Linear
• 120° & 90° bond angles
• use empty d orbitals from valence shell
• d orbitals can be used to make p bonds
Tro, Chemistry: A Molecular
Approach 171
••
I
F
F
O
O
O
••
••
••
••
••
••
••
••
••
••
••
••
-1
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Slide 172
Tro, Chemistry: A Molecular
Approach 172
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Slide 173 sp3dHybridized AtomsOrbital Diagrams
Tro, Chemistry: A Molecular
Approach 173
Unhybridized atom
3s 3p
sp3d hybridized atom
3sp3d
S
3s 3p
3sp3d
P
3d
3d
(non-hybridizing d orbitals not shown)
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Slide 174 sp3d2
• atom with 6 areas of electrons around it
• octahedral shape
• Square Pyramid, Square Planar
• 90° bond angles
• use empty d orbitals from valence shell
• d orbitals can be used to make p bonds
Tro, Chemistry: A Molecular
Approach 174
•• •
•
••
••
••Br
F
F
F
F
F••••
••
•• ••••
•• ••
••
••
••
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Slide 175
Tro, Chemistry: A Molecular
Approach 175
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Slide 176 sp3d2 Hybridized AtomsOrbital Diagrams
Tro, Chemistry: A Molecular
Approach 176
Unhybridized atom sp3d2 hybridized atom
S
3s 3p 3sp3d2
↑↓
3d
↑↓ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑
I
5s 5p
↑↓
5d
↑↓ ↑↓ ↑
5sp3d2
↑↓ ↑ ↑ ↑ ↑ ↑
(non-hybridizing d orbitals not shown)
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Slide 177
Tro, Chemistry: A Molecular
Approach 177
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Slide 178 Example - Predict the Hybridization of All the Atoms in H3BO3
Tro, Chemistry: A Molecular
Approach 178
O B
O
OH H
H••
••
••
••
••
••
H = can’t hybridize
B = 3 electron groups = sp2
O = 4 electron groups = sp3
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Slide 179 Practice - Predict the Hybridization and Bonding Scheme of All the Atoms in NClO
Tro, Chemistry: A Molecular
Approach 179
O N Cl ••••
••
••
••••
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Slide 180 Practice - Predict the Hybridization and Bonding Scheme of All the Atoms in NClO
Tro, Chemistry: A Molecular
Approach 180
O N Cl ••••
••
••
••••
N = 3 electron groups = sp2
O = 3 electron groups = sp2
Cl = 4 electron groups = sp3
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Slide 181 Predicting Hybridization and Bonding Scheme1) Start by drawing the Lewis Structure
2) Use VSEPR Theory to predict the electron group geometry around each central atom
3) Use Table 10.3 to select the hybridization scheme that matches the electron group geometry
4) Sketch the atomic and hybrid orbitals on the atoms in the molecule, showing overlap of the appropriate orbitals
5) Label the bonds as s or p
Tro, Chemistry: A Molecular
Approach 181
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Slide 182
Draw the Lewis Structure
Predict the electron group
geometry around inside
atoms
C1 = 4 electron areas
C1= tetrahedral
C2 = 3 electron areas
C2 = trigonal planar
Tro, Chemistry: A Molecular Approach 182
Ex 10.8 – Predict the hybridization and bonding scheme for CH3CHO
C1H
H
H
C2 H
O
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Slide 183
Determine the hybridization
of the interior atoms
C1 = tetrahedral
C1 = sp3
C2 = trigonal planar
C2 = sp2
Sketch the molecule and
orbitals
Tro, Chemistry: A Molecular Approach 183
Ex 10.8 – Predict the hybridization and bonding scheme for CH3CHO
C1H
H
H
C2 H
O
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Slide 184
Label the bonds
Tro, Chemistry: A Molecular Approach 184
Ex 10.8 – Predict the hybridization and bonding scheme for CH3CHO
C1H
H
H
C2 H
O
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Slide 185 Problems with Valence Bond Theory• VB theory predicts many properties better than Lewis Theory
• bonding schemes, bond strengths, bond lengths, bond rigidity
• however, there are still many properties of molecules it doesn’t predict perfectly
• magnetic behavior of O2
Tro, Chemistry: A Molecular
Approach 185
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