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.
jelly beans, gum drops or gumballs; toothpicks; twist ties; colored pencils or crayons
Identify the chemical and structural formulas and electron dot structures of the following molecules:
water, ammonia, carbon dioxide, fluorine, methane, ethane
Write the formulas and draw the two-dimensional structures in the table.
Chose one color candy to represent each atom of an element (e.g., red jelly bean = hydrogen). Create a key that identifies each element.
Use the candy, toothpicks, and/or twist ties to construct a three- dimensional model of each of the aforementioned molecules.
Draw, as accurately as possible, each model in the table.
Answer the questions.
Compare the information provided by a molecules chemical formula to the information provided by its structural formula.
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?
Identify the bond types between the carbon and the two oxygen atoms in the carbon dioxide molecule.
Explain why it is difficult to accurately represent ammonia two- dimensionally.
What is the major difference between the two-dimensional and three- dimensional models of ethane and methane? When might you choose to use a two-dimensional model rather than a three-dimensional model when representing one of the molecules?