Wednesday, August 15, 2012

More bead/rubber band models

I found that it is much easier to use commercial beads to make the so called styrofoam/rubber band models of L. C. King. According to Prof. H. A. Bent, every student of chemistry should make a set of this kind of models for learning the concept of chemical bond. Here, I will show how to make valence sphere models using 25mm wooden beads and rubber band with 8mm small plastic beads as endcaps.

1. To make the valence sphere model of a methane which has the tetrahedral shape, we can connect two wooden beads (two-bead unit) first as shown in the following picture:

Then cross two two-bead units with each other to get a tetrahedral methane:

2. We can easily generalize the procedure to molecules with six valencies. First make another two-bead units with rubber bands, then cross it around the tetrahedral four-bead unit we just made. Then one should get an octahedral arrangement of six beads as shown in the following picture:

3. One can also try to make a five-bead unit which represents the valence sphere model of a molecule with dsp3 hybridization.

4. Valence sphere models for molecules with more than one center such as the ethane can easily be made too. Here is my procedure for making the valence sphere model of an ethane molecule: first I connect a three-bead unit and two two-bead units as shown in the following picture.

Then, connect these three units at suitable positions, one should get the valence sphere model for the ethane.

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