10.14 - Chemistry 102B Discussion Worksheet#13 Valence...

Chemistry 102B – Discussion Worksheet #13
Valence Shell Electron Pair Repulsion (VSEPR) Model
The shapes of molecules can be predicted from their Lewis structures by
using the VSEPR ( V alence S hell E lectron P air R epulsion) model, which
states that electron pairs around a central atom will assume a geometry
that keeps them as far apart from each other as possible.
There are five base geometries:
Octahderal - Six groups surrounding a central atom will form an
octahedron. All of the groups in this structure at 90 ° or 180 ° to each other.
All positions are equivalent.
Trigonal bipyramid – Five groups will form a trigonal bipyramid. The two
positions pointing up and down are called axial positions. They are 180 °
to each other, and at 90 ° to the other three, equatorial positions. The
three equatorial positions are at 120 ° to each other. There is more room in
the equatorial positions, and large groups will occupy these positions.