1. Molecular Shapes Chapter 6 Section 3

2. Lewis dot structures show how atoms are bonded together, but they often do not illustrate the true shape of a molecule. The shape of a molecule is determined by Valence Shell Electron Pair Repulsion Theory (VSEPR)

3. VSEPR theory says that pairs of electrons around a central atom want to be as far away from each other as possible. For example, if you have two atoms bonded to a central atom, like CO 2, the molecule will form in a straight line. This is a Linear shape

4. When you have three atoms bonded to a central atom, with no lone pairs, the molecule forms a Trigional Planar shape. Generally, this only occurs with Boron containing molecules.

5. When you have four atoms surrounding a central atom, like in CH 4 the molecule takes a tetrahedral shape.

6. When you have three atoms surrounding a central atom and a lone pair of electrons, the molecule takes on a Trigional Pyramidal shape. Remember, lone pairs take up space!

7. Lone pairs of unbonded electrons still take up space, even though you cannot see them in the shape of the molecule. Therefore, a molecule like H 2 S will have a Bent shape.

8. If you have 5 atoms around a central atom, like in PF 5, the shape the molecule forms is called Trigonal Bipyramidal

9. And finally, if you have 6 atoms around a central atom, like in SF 6, the molecule forms an Octahedral shape.