1. Molecular geometry predicted by VSEPR
Awesome resource: for 3D visuals
Awesome teacher’s resource: for 3D visuals

3. Molecular geometry: linear
a. BeH2
Lewis structure:
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 2
AX2
Linear
Molecular geometry: linear

4. b) BH3 Lewis structure: Molecular geometry: Trigonal planar
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 3
AX3
Trigonal planar
Molecular geometry: Trigonal planar

5. 2 1 3 AX2E1 Trigonal planar c) SO2 Lewis structure:
Treat each DB as a single bond (bonding pair)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 2 1 3
AX2E1
Trigonal planar
Electronic geometry differs from molecular geometry because of the lone pair
Molecular geometry: bent

6. 4 AX4 Tetrahedral d) NH4+ Lewis structure:
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 4
AX4
Tetrahedral
CH4 also has tetrahedral geometry
Molecular geometry: Tetrahedral

7. 3 1 4 AX3E Tetrahedral e) NH3 Lewis structure:
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 3 1 4
AX3E
Tetrahedral
Again, electronic geometry differs from molecular geometry because of the lone pair
Molecular geometry: Trigonal pyramidal

8. Do you remember the hybridization scheme for Oxygen in water?
f) H2O
Lewis structure:
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 2 4
AX2E2
Tetrahedral
What causes electronic geometry to be different from molecular geometry ?
Molecular geometry: Bent
Do you remember the hybridization scheme for Oxygen in water?

9. Molecular geometry: Trigonal bipyramidal
g) PCl5
Lewis structure:
(doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 5
AX5
Trigonal bipyramidal
Bi: two
Bipyramidal: 2 pyramids stacked on top of one another
Molecular geometry: Trigonal bipyramidal

10. Molecular geometry: see saw
h) SF4
Lewis structure:
(3rd period element; doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 4 1 5
AX4E
Trigonal bipyramidal
Molecular geometry: see saw

11. Molecular geometry: T-shape
i) ClF3
Lewis structure:
(3rd period element; doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 3 2 5
AX3E2
Trigonal bipyramidal
Molecular geometry: T-shape

12. Molecular geometry: Linear
j) XeF2
Lewis structure:
(doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 2 3 5
AX2E3
Trigonal bipyramidal
What’s there
Molecular geometry: Linear

13. Molecular geometry: Octahedral
k) SF6
Lewis structure:
(doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 6
AX6
Octahedral
Molecular geometry: Octahedral

14. Molecular geometry: Square pyramidal
l) IF5
Lewis structure:
(doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 5 1 6
AX5E
Octahedral
Molecular geometry: Square pyramidal

15. Molecular geometry: Square planar
m) XeF4
Lewis structure:
(doesn’t obey octet)
# Bond pairs
# Lone pairs
Total pairs
General formula
Electronic geometry 4 2 6
AX4E2
Octahedral
What’s there
What we see
Molecular geometry: Square planar

16. The table ends here.
The following slides are meant for further enrichment & practice opportunity on the topic of VSEPR

17. Chemical Bonding II The Effect of Lone Pairs
lone pair groups “occupy more space” on the central atom
relative sizes of repulsive force interactions is:
Lone Pair – Lone Pair > Lone Pair – Bonding Pair > Bonding Pair – Bonding Pair
this effects the bond angles, making them smaller than expected

18. Recap

20. Practice – Predict the Molecular Geometry and Bond Angles in SiF5─ Do it yourself first, answer is on next slide

21. Practice – Predict the Molecular Geometry and Bond Angles in SiF5─-
Si Least Electronegative
5 Electron Groups on Si
Si Is Central Atom
5 Bonding Groups
0 Lone Pairs
Si = 4e─
F5 = 5(7e─) = 35e─
(─) = 1e─
total = 40e─
Shape = Trigonal Bipyramid
Bond Angles
Feq-Si-Feq = 120°
Feq-Si-Fax = 90°

22. Practice – Predict the Molecular Geometry and Bond Angles in ClO2F (Chloryl Fluoride)

23. Practice – Predict the Molecular Geometry and Bond Angles in ClO2F
Cl Least Electronegative
4 Electron Groups on Cl
Cl Is Central Atom
3 Bonding Groups
1 Lone Pair
Cl = 7e─
O2 = 2(6e─) = 12e─
F = 7e─
Total = 26e─
Shape = Trigonal Pyramidal
Bond Angles
O-Cl-O < 109.5°
O-Cl-F < 109.5°

24. Representing 3-Dimensional Shapes on a 2-Dimensional Surface
Chemical Bonding
Representing 3-Dimensional Shapes on a 2-Dimensional Surface
one of the problems with drawing molecules is trying to show their dimensionality
by convention, the central atom is put in the plane of the paper
put as many other atoms as possible in the same plane and indicate with a straight line
for atoms in front of the plane, use a solid wedge
for atoms behind the plane, use a hashed wedge

25. Representing 3-Dimensional Shapes on a 2-Dimensional Surface

27. Multiple Central Atoms
many molecules have larger structures with many interior atoms
we can think of them as having multiple central atoms
when this occurs, we describe the shape around each central atom in sequence e.g. acetic acid
shape around left C is tetrahedral
shape around center C is trigonal planar
shape around right O is tetrahedral-bent

28. Describing the Geometry of Methanol

29. Describing the Geometry of Glycine

30. Practice – Predict the Molecular Geometries in H3BO3
Tro, Chemistry: A Molecular Approach

31. Practice – Predict the Molecular Geometries in H3BO3
oxyacid, so H attached to O
3 Electron Groups on B
4 Electron Groups on O
B Least Electronegative
O has
2 Bonding Groups
2 Lone Pairs
B has
3 Bonding Groups
0 Lone Pairs
B Is Central Atom
B = 3e─
O3 = 3(6e─) = 18e─
H3 = 3(1e─) = 3e─
Total = 24e─
Shape on B = Trigonal Planar
Shape on O = Bent

32. Practice – Predict the Molecular Geometries in C2H4
Tro, Chemistry: A Molecular Approach

33. Practice – Predict the Molecular Geometries in C2H4
3 Electron Groups on C
C = 2(4e─) = 8e ─
H = 4(1e─) = 4e─
Total = 12e─
0 Lone Pairs
Shape on each C = Trigonal Planar

34. Practice – Predict the Molecular Geometries in CH3OCH3

35. Practice – Predict the Molecular Geometries in Dimethyl Ether (CH3OCH3)
4 Electron Groups on C
C = 2(4e─) = 8e ─
H = 6(1e─) = 6e─
O = 6(1e─) = 6e─
Total = 20e─
2 Lone Pairs on O
Shape on each C = Tetrahedral
Shape on O = Bent

36. Reminder about Eletronegativity!
Electronegativity, is a chemical property that describes the tendency of an atom to e- towards itself