1. Theories of Bonding & Structure
Review Chapter 10:
Theories of Bonding & Structure
Chemistry: The Molecular Nature of Matter, 6th edition
By Jesperson, Brady, & Hyslop

2. Chapter 10 Concepts VESPR theory
Predict molecular geometry & overall dipole moment
Valence Bond Theory
Identify & draw hybridization of orbitals at central atom
Identify & draw σ and π bonds
Molecular Orbital Theory
Draw MO Energy Diagrams to identify
Bond Order
Number of Unpaired Electrons

3. Memorize Linear Trigonal Planar Trigonal Bipyramidal Tetrahedral
Planar Triangular
Trigonal Bipyramidal
Tetrahedral
Octahedral

4. Distorted Tetrahedron
Memorize
T-shaped
Square
Pyramid
Planar
Trigonal Pyramidal
Bent
Seesaw or
Distorted Tetrahedron

5. Determining 3-D VESPR Stuctures
1. Draw Lewis Structure of Molecule
Don't need to compute formal charge
If several resonance structures exist, pick only one
2. Count electron pair domains
Lone pairs and bond pairs around central atom
Multiple bonds count as one set (or one effective pair)
3. Arrange electron pair domains to minimize repulsions
Lone pairs
Require more space than bonding pairs
May slightly distort bond angles from those predicted.
In trigonal bipyramid lone pairs are equatorial
In octahedron lone pairs are axial
Name molecular structure by position of atoms—only bonding electrons

6. Polarity
If symmetrical polar bonds around a central atom then they cancel and there is no overall dipole moment.
Molecule is usually polar if
All atoms attached to central atom are NOT same, OR
There are one or more lone pairs on central atom
EXCEPT:

7. Valence Bond Theory Hybridization = mixing atomic orbitals sp: Linear
Individual atoms, each have their own orbitals and orbitals overlap to form bonds. Extent of overlap of atomic orbitals is related to bond strength
Hybridization = mixing atomic orbitals
sp: Linear
sp3d: Trigonal
Bipyramidal
sp2: Planar
Triangular
sp3d2: Octahedral
sp3: Tetrahedral

8. Valence Bond Theory Draw lewis dot structure
How many lone pairs & bonded atoms will repel one another? That is the number of hybrid orbitals needed
2: sp 3: sp2 4: sp3 5: sp3d 6: sp3d2
Convert the needed number of atomic orbitals into hybridized orbitals.
Fill in valence electrons. Remember that any p orbitals will be close enough in energy that they both hybrid & remaining p orbitals will fill half way with electrons before they pair.
Draw hybrid orbitals equally spaced around the central atom:
Form σ bonds using hybrid orbitals with one electron
Hybrid orbitals with two electrons are likely lone pairs
If any lone electrons are in p orbitals π bonds will form
Describe molecular geometry around central atom(s).

9. Valence Bond Theory: Example N2
:NN: p p sp E s
Hybrid & AO of N
AO of N
Lone pair and atom bonded to Nitrogen will repel each other.
Therefore, need to hybridize 2 orbitals
One hybrid orbital with one electron will participate in a σ bond with the other nitrogen
The other hybrid orbital contains a lone pair
2 p orbitals each have 1 electron so form 2 π bonds to the other nitrogen

10. Molecular Orbital Theory Molecular Orbital Theory
Views molecule as collection of positively charged nuclei having a set of molecular orbitals that are filled with electrons (similar to filling atomic orbitals with electrons). Doesn't worry about how atoms come together to form molecule

11. Molecular Orbital Theory
O2, F2 and Higher 2p Lower in energy than 2p
Li2  N2
2p Lower in energy than 2p
Can ignore filled 1s bonding & antibonding and focus on valence electrons

12. Molecular Orbital Theory: Diagramsσ* π* p π E σ σ* s σ
AO of one atom
AO of second atom

13. For the following molecules:
Problem
Set A
For the following molecules:
Draw a lewis dot structure.
Determine the molecular geometry at each central atom.
Identify the bond angles.
Identify all polar bonds: δ+ / δ-
Assess the polarity of the molecule & indicate the overall dipole moment if one exists
AsF5 AsF3 SeO2 GaH3
ICl2- SiO TeF6

14. Problem
Set B
What is the hybridization of oxygen in OCl2?
For the species and XeF4O, determine the following:
electron domain geometry (geometry including non-bonding pairs)
molecular geometry
Hybridization around central atom
Polarity
How many  and  bonds are there in CH2CHCHCH2, and what is the hybridization around the carbon atoms?
Draw & list the bonding orbitals for HCN.

15. What is the bond order & number of unpaired electrons in
Problem
Set C
What is the MO Energy Diagram for B2? How many unpaired electrons does B2 have?
What is the bond order & number of unpaired electrons in
Draw the MO Energy Diagram for BN.

16. Problem
Set A

17. Problem
Set A

18. Problem
Set A

19. Problem
Set B
sp3
XeF4O: octahedral, square pyramid, sp3d2, polar
9, 2, sp2
HCN: C will be create a σ bond to H and N with sp2 hybridized orbitals and use 2 p orbitals to participate in 2 π bonds with N. N will participate in the σ bond with C with an sp2 hybridized orbital, the other will hold the N lone pair, and then N will use 2 p orbitals to π bond with C.

20. B2 BN MO B2: unpaired e- = 2 O2: BO = 2 unpaired e- = 2
Problem
Set C B2 BN σ* σ* π* π*
MO B2:
unpaired e- = 2
O2: BO = 2 unpaired e- = 2
O2+: BO = 5/2 unpaired e- = 1
O2- : BO = 3/2 unpaired e- = 1
MO BN: σ σ π π σ* σ* σ σ

21. More Practice Problems:
Analyze the following compounds:
Draw the lewis dot structure
Determine the Geometry using VESPR theory
Determine the hybridization at any central atoms using VB Theory
Draw & Describe bonding in VB terms: ie # of sigma vs pi bonds
H2S
SO2
H2C=C=CH2
HCOCl