This activity is meant to be used after students have done the simulator-based activity, had some notes to introduce the concepts of VSEPR, and drawn some molecules while identifying the 3D shapes. The prior experience will make it easier to build the correct models with the kits for this activity.
In this activity you will review the names of the shapes of molecules from the VSEPR (Valence Shell Electron Pair Repulsion) model and build molecules using a model kit. The idea is to make the shapes more visible to your imagination by making them concrete and hands-on. Work in groups of two to four students to complete this activity.
Review the shapes of molecules as predicted by the VSEPR Model. Use the given numbers of bonds and and lone pairs in each row to fill in the rest of each row. One is done for you to show you how it works.
Number of Bonds
Number of Lone Pairs
Total Number of Electron Domains
Electron Geometry
Molecule Geometry
Bond Angles
Drawing
1
0
2
0
3
0
2
1
4
0
3
1
4
tetrahedral
trigonal pyramidal
109.5°
2
2
5
0
4
1
3
2
6
0
5
1
4
2
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Part I
You will be using a molecular model kit, which contains:
3 black carbon atoms
2 red oxygen atoms
1 blue nitrogen atom
9 white hydrogen atoms
12 short bonds
4 long bonds
What to do:
Build a 3-D model of each molecule below using the kit provided.
Most models you build will have a bond at every bonding site (or hole) on every atom. Only one does not.
Double or triple bonds are made using the long bonds, which bend.
After you build the molecule with the kit, draw a Lewis diagram for each one.
After building the model and drawing the Lewis diagram: identify the 3-D shape or shapes using the model and your drawing. Molecules with two or more ‘central’ atoms will have a shape name for each one. The shape names are: linear, trigonal planar, bent (120° angles), tetrahedral, trigonal pyramidal, bent (109.5° angles).
CO2
Lewis Structure:
VSEPR Shape:
H2CO
Lewis Structure:
VSEPR Shape:
NO2–
not all holes are filled for this model!
Lewis Structure:
VSEPR Shape:
CH4
Lewis Structure:
VSEPR Shape:
NH3
Lewis Structure:
VSEPR Shape:
H2O
Lewis Structure:
VSEPR Shape:
C2H6
Lewis Structure:
VSEPR Shapes:
C2H4
Lewis Structure:
VSEPR Shapes:
CH4O
Lewis Structure:
VSEPR Shapes:
C2H6O
Lewis Structure:
VSEPR Shapes:
C2H6O
a different structure
Lewis Structure:
VSEPR Shapes:
CH3CHO
Lewis Structure:
VSEPR Shapes:
C2H4O2
both oxygen atoms attach to the same carbon atom
Lewis Structure:
VSEPR Shapes:
C2H5NO
the oxygen and nitrogen atoms attach to the same carbon atom
Lewis Structure:
VSEPR Shapes:
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Part II
Put away the model kit used in Part I. The Inorganic Model Set you will use for the molecules below contains
1 black carbon atom (4 holes)
4 red oxygen atoms (2 holes)
2 blue nitrogen atoms (3 holes)
1 yellow sulfur atom (6 holes)
1 purple phosphorus atom (3 holes)
2 green halogen atoms (1 hole)
2 gray metal atoms (6 holes)
1 brown atom (5 holes)
4 white hydrogen atoms (1 hole)
14 short bonds
6 long bonds
What to do:
Count valence electrons and draw Lewis structures for each molecule. Do this before building a 3D model.
Build a 3-D model of each molecule below using the kit provided.
Since there may not be enough atoms in your kit for ligand atoms, simply use bonds and your imagination to build some molecules.
Some molecules will have atoms with empty holes that represent lone pairs. Refer to your Lewis diagram for guidance.
Double or triple bonds are made using the long bonds, which bend.
After building the model and drawing the Lewis diagram: identify the 3-D shape or shapes using the model and your drawing. The shape names are: trigonal bipyramidal, see-saw, t-shaped, octahedral, square pyramidal, square planar, and linear.
