Modeling Molecules

Modeling Molecules

Introduction:

You can represent a molecule two-dimensionally, as a structural formula or electron dot structure. Although such models are useful in certain contexts, they do not accurately represent bond angles between atoms or shapes of molecules. In this activity, you will construct three-dimensional models of several molecules. You will use electron dot structures and structural formulas to inform how you construct the three-dimensional models.

Materials:

jelly beans, gum drops or gumballs; toothpicks; twist ties; colored pencils or crayons

Procedure:

1. Identify the chemical and structural formulas and electron dot structures of the following molecules:

water, ammonia, carbon dioxide, fluorine, methane, ethane

2. Write the formulas and draw the two-dimensional structures in the table.

3. Chose one color candy to represent each atom of an element (e.g., red jelly bean = hydrogen). Create a key that identifies each element.

4. Use the candy, toothpicks, and/or twist ties to construct a three- dimensional model of each of the aforementioned molecules.

5. Draw, as accurately as possible, each model in the table.

6. Answer the questions.

Table:

Molecule name
Chemical formula
Electron dot structure
Structural formula
Drawing of model

Water

H2O

H2O

Ammonia

NH3

NH3

Carbon dioxide

CO2

CO2

Fluorine

F

F

Methane

CH4

CH4

Ethane

C2H6

C2H6

Questions:

1. Compare the information provided by a molecules chemical formula to the information provided by its structural formula.

They are the same. I think? That’s what I found.

2. Fluorine is a toxic, reactive gas. Which representation (structural formula, electron dot structure, or three-dimensional model) would you use to explain why fluorine so reactive? Why?

One reason