Modeling Molecules

Introduction

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
Key:
Questions:
1.Compare the information provided by a molecules chemical formula tothe information provided by its structural formula.
2.Fluorine is a toxic, reactive gas. Which representation (structuralformula, electron dot structure, or three-dimensional model) wouldyou use to explain why fluorine
so reactive? Why?
3.Identify the bond types between the carbon and the two oxygen atomsin the carbon dioxide molecule.
4.Explain why it is difficult to accurately represent ammonia two-dimensionally.
5.What is the major difference between the two-dimensional and three- dimensional models of ethane and methane? When might you chooseto use a two-dimensional model
rather than a three-dimensional modelwhen representing one of the molecules?
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