Molecular Geometry and Polarity

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CHM 114 Activity

Molecular Geometry and Polarity

In this activity you will:

1. Use VSEPR theory to predict electron domain geometries and molecular shapes of molecules with single or multiple central atoms.

2. Describe electron domain geometries and molecular shapes with bond angles.

3. Practice drawing Lewis Structures.

4. Determine whether a molecule is polar or nonpolar from its 3-dimensional shape.

Part 1: Using Lewis Structures to Predict Electron-Domain Geometries

(Valence Shell Electron Pair Repulstion (VSEPR) Theory)

Before starting this activity, make sure you have mastered the procedure for drawing Lewis structures described in Chapter 8. See the procedure and examples in Section 8.5 of your textbook. Before you can determine the shape of a molecule, you must start with a correct Lewis structure. Also, read the definitions and Table 9.1 provided here before proceeding.

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1. Consider the ozone molecule, O3, and its Lewis structure shown above.

a) How many electron domains are there around the central oxygen atom?

|Trigonal Planar |

b) What is its electron domain geometry?

|120 degrees |

c) What is the O–O–O bond angle?

Molecules with More than One Central Atom

2. Cysteine is an amino acid thought to be a detoxifying agent, an important component of the antioxidant defenses of the body. The structural formula and Lewis structure for cysteine are shown below.

(a) Complete the Lewis stucture by adding nonbonding electrons (to complete octets). You can do this on scratch paper or a paper copy of this activity. You don’t have to draw on the electronic file....