The document discusses how Lewis dot diagrams can be used to predict the 3D structure of molecules. It describes 5 main types of molecular geometries: 1) linear, 2) angular/bent, 3) trigonal planar, 4) trigonal pyramidal, and 5) tetrahedral. Each geometry has characteristic bond angles that are determined by the number of bonding pairs and lone pairs on the central atom. Examples are provided for common molecules that exhibit each type of 3D structure.

1. From Lewis Dot Diagrams to
3D Diagrams

2. From Lewis Dot Diagrams to 3D Diagrams
Legend:
A = Central atom
X = Bonding pair
E = Lone pair
O HH
A
X
E

3. Linear
2 types
1. a)
b)
From Lewis Dot Diagrams to 3D Diagrams

4. From Lewis Dot Diagrams to 3D Diagrams
Examples:
HCl, HF, O2
(all diatomic molecules)
1. a) Linear
Lewis diagram 3D diagram
180º
ClH ClH

5. From Lewis Dot Diagrams to 3D Diagrams
1. b) Linear
Lewis diagram 3D diagram
CO CO
Examples:
CO2, BeCl2, HgCl2
180º
O O

6. Overall look
Angular or Bent
2 types
2. a)
b)
From Lewis Dot Diagrams to 3D Diagrams

7. 2. a) Angular/Bent
Examples:
SO2, NO2
-, O3
<120º
From Lewis Dot Diagrams to 3D Diagrams
Lewis diagram 3D diagram
SO S
O
O
O

8. 2. b) Angular/Bent
From Lewis Dot Diagrams to 3D Diagrams
Lewis diagram 3D diagram
OH O
H
H
H
Examples:
H2O, OF2
<<109.5º

9. Why are the bond angles different?
<120º
vs.
A lone pair is less confined in space and exerts greater
repulsions on nearby bonding pairs.
As a result, bonding pairs are pushed farther away from
the lone pairs.
<<109.5º
From Lewis Dot Diagrams to 3D Diagrams

10. Trigonal planar
1 type
3.
From Lewis Dot Diagrams to 3D Diagrams

11. O
3. Trigonal planar
From Lewis Dot Diagrams to 3D Diagrams
Lewis diagram 3D diagram
SO
S
O
O
O
120º
Examples:
SO3, BF3, NO3
-, CO3
2-
O

12. Trigonal pyramidal
1 type
4.
From Lewis Dot Diagrams to 3D Diagrams

13. H
H
4. Trigonal pyramidal
From Lewis Dot Diagrams to 3D Diagrams
Lewis diagram 3D diagram
NH NH H
H
<109.5º
Examples:
NH3, PCl3

14. Tetrahedral
1 type
5.
From Lewis Dot Diagrams to 3D Diagrams

15. H
H
H
5. Tetrahedral
From Lewis Dot Diagrams to 3D Diagrams
Lewis diagram 3D diagram
CH CH H
H
Examples:
CH4, PO4
3-, SO4
2-, ClO4
-
109.5º
H