Fifty teaching ideas
Teaching resource 11
Principles of molecular shape: Tetrahedron
You will need:
1 black carbon Ck
4 green halogen Cla
grey straws
The positions of the bonds from an atom are determined by the fact that the electron pairs forming the bonds
repel each other electrostatically.
Tetrachloromethane CCl4 has four electron-pair bonds C-Cl. Construct a model of the molecular CCl4 using a
black carbon centre Ck and 4 green chlorine centres Cla linked by straws.
Thread a piece of cotton thought the chlorine atoms as shown in
figure 1.
The shape formed is a triangular pyramid or tetrahedron.
Figure 1 Tetrachloromethane
Discuss:
The angle between adjacent bonds. Are they all equal?
Is it possible to devise a shape for CCl4 where bond angles are greater than this?
Products which can be used for this demonstration:
0045 Orbit Foundation Set
0046 Orbit Basic Structures Class Set | 0026 Orbit Basic Structures Individual Set
0047 Orbit Organic/Inorganic Class Set | 0028 Orbit Organic/Inorganic Individual Set
0041 Large Class set
Or you can order sufficient individual atoms from the Orbit, Minit or Unit systems for your individual needs.
The angle between the bonds is 109° 28’. They are all equal. It is not possible to create a shape with larger angles.
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