 And this is where the VS-EPR model comes in. VS-EPR stands for Valence Shell Electron-Pair Repulsion. And in the next video I'll explain what that means and how the theory works. The VS-EPR model can tell you about how the bonded atoms are arranged in space and therefore what the overall shape of the molecule is. In the case of trichloromethane, VS-EPR predicts that the shape of the molecule is like this, which is what we call tetrahedral, because the four outer atoms are at the vertices of a tetrahedron. Represented as what we call a ball and stick structure, you can clearly see the 3D shape of the molecule. And when we add more complex computer modelling of the electron clouds of the atom, you can really see that the shape of the molecule is a sort of blobby distorted pyramid shape. This last picture here contains more information than VS-EPR can provide. Nothing in VS-EPR lets you accurately draw the electron clouds like this. But it does illustrate the levels of complexity as you work from a simple model like the Lewis structure up to models that more and more closely represent reality. Incidentally, these coloured pictures here come from the Chem-Ed DL site, which has a database of 3D computer models of molecule shapes. And we'll be using these quite a lot in later videos.