Molecular Structure Lab ` Name ____________________________________

In covalent molecules, single, double and triple bonds form between atoms. In some cases, the atoms are arranged in straight chains. At other times, the chains are branched. Still other molecules take the form of a ring of atoms.

Sometimes a given molecular formula might represent more than one compound. For example, C₂H₆O represents both ethanol and dimethyl ether, compounds with different structural formulas and different properties.

Ethanol Dimethyl Ether

Substances having the same chemical formula, but different structures are called structural isomers. They are completely different chemicals.

OBJECTIVES

1. Construct models of some simple and more complicated covalent molecules.

2. Draw structural formulas showing the shape of molecules.

3. Construct more than one structure for some of the molecules represented.

PRE-LAB Questions

1. Draw the electron dot diagram for the following atoms ON YOUR OWN PAPER.

H C N O Cl

2. Based on the electron dot diagrams you just drew, how many bonds can each of the atoms above form.

PROCEDURE

1. Models often use different colors to represent different types of atoms. Choose one color of candy to represent each of the types of atom above. H will be represented by a marshmallow. Toothpicks will serve as the bonds.

2. Construct models of the following molecules. There is only one formula for each. When you are satisfied that you have the correct structure, sketch it on your paper.

H₂O CH₄ CH₃OH CCl₄

3. For the following molecular formulas, there can be more than one arrangement of the atoms. Make the isomers indicated for each by following the rules you wrote for bonds. Sketch a structural formula for each isomer on your paper. Make sure that the order of atoms has changed.

a. butane C₄H₁₀ (Draw 2 isomers)

b. butanol C₄H₁₀O (Draw 3 isomers)

c. hexane C₆H₁₄ (Draw 3 isomers)

d. dichloroethane C₂H₄Cl₂ (Draw 2 isomers)

4. All of the models of molecules so far include only single bonds. The following group of molecules contain single, double and triple bonds. Make each structure, and then sketch the structural formula for each isomer of the molecules on your paper.

a. carbon dioxide CO₂

b. nitrogen N₂

c. butene C₄H₈ (Draw 2 isomers)

d. butyne C₄H₆ (Draw 2 isomers)