Lab #4: Molecular Models
Names ______________________________
_________________________________
Objectives:
-Determine the 3D shape of compounds using Valence Shell Electron Pair Repulsion (VSEPR)
theory
-Make models of the molecules using the molecular modeling kits
Notes:
Use the following colors for the corresponding atoms
Hydrogen
White
Halogens (Cl, F)
Green
Phosphorus
Purple
Oxygen
Red
Carbon
Black
Nitrogen
Blue (4 holes)
Boron
Blue (5 holes)
Barium
Silver (2 holes)
Sulfur in SO2, SH2
Yellow (4 holes)
Sulfur in SCl5, SF6
Yellow (6 holes)
Xenon
Brown (6 holes)
Use the short grey bonds for single bonds, and the longer, flexible grey bonds for each bond
in a double bond
Procedures:
1. Draw electron dot structures for the first of the compounds listed below. Draw the
molecule such that the distance between lone pairs around the central atom is maximized.
Using VSEPR theory, assign a shape to the compound.
2. Using the molecular model kit and the appropriate “atoms” and “bonds,” create models of
the molecule. Verify that the shape you assigned using VSEPR is correct.
3. Draw a picture of the 3D compound in your notebook.
4. Record the # lone pairs, total # of atoms and the shape of the compound in a table in your
notebook
Data:
Compound
# lone pairs
Bonded Atoms
(around central atom)
Shape
H2
N2
SH2
SO2
CO2
BaCl2
BH3
NH3
CF4
XeF4
PF5
SCl5
SF6
Post-Lab Question (be as detailed and complete as possible):
1. SO2, CO2 and BaCl2 all have 3 atoms, but have varying numbers of bonds and shapes.
Discuss what it is about these molecules that cause both the similarities and the differences
in shape.
2. Similarly, NH3 and BH3 have 4 total atoms, but have different shapes, while CF4 and XeF4
have 5 atoms but different shapes. Why is this?
3. Why can Sulfur form up to 6 bonds, but Boron can only form 3 and Carbon can only form
4?
4. What effect do double bonds have, if any, on a compound’s shape?
5. Using the information you collected in the table above, can you make some general rules
about what structure a compound will have given a set number of lone pairs and bonded
atoms?