Chemistry

In this experiment, you will predict the three-dimensional geometry of a series of neutral molecules using the VSEPR theory. PROCEDURE Part 1: The Periodic Table 1. Use the Periodic Table of Elements to determine the elemental symbol, group number, and valence electrons for the elements listed in Table 1 on the Experiment 1 Data Sheet. Record this data in Table 1. 2. Use colored pencils and the data in Table 1 to sketch a Lewis Dot Structure for each element in Table 1 on the Data Sheet. ©2018, eScience Labs Part 2: Construction of Molecules 1. Now, construct the three-dimensional geometry for the molecules listed in Table 2 on the Data Sheet. While you are constructing your molecules, keep the following points in mind: • Nature “loves” symmetry, which means equal bond lengths and angles. • Electrons prefer to be as far apart from each other as possible without disrupting the symmetry too drastically. • Lone pairs take up more space because they are not confined by bonds, and are localized. 2. Look at Table 2 on the Data Sheet, and fill in the bond angles for each molecule you will be building. Hint: Use the column in Table 2 on the Data Sheet labeled “Structure” to determine the molecular geometry. 3. Using colored pencils, make a Lewis Dot Structure sketch for each molecule in Table 2 you will be building. 4. Gather as many marshmallows and toothpicks you will need for building your first molecule (carbon dioxide). Hint: You will need two marshmallows for the oxygen (O), and one marshmallow for the carbon (C). 5. Using the permanent marker, label the miniature marshmallow with the elemental symbol for each atom in your molecule (Figure 19). 6. Refer to the first column in Table 2 to determine the central atom in your molecule. 7. Connect the atoms together with toothpicks. 8. Compare your model with the diagram of the Linear molecular geometry in Table 2. 9. Use your protractor to verify that you have constructed your molecule with the correct bond angles. 10.To determine the angle between your atoms, place the center of the protractor on the central atom, and align the base with a bond (Figure 19). Then measure the angle. When in doubt, think “Should this angle be bigger or smaller than 90°?” 11. If your bond angles are incorrect, remove the toothpicks from the marshmallows, construct the molecule again, and use your protractor to verify that you have constructed your molecule with the correct bond angles. 12.Follow the above procedures for each molecule in Table 2. 13.When you are finished, take a picture of the molecules and send the images to your instructor. Make sure you identify yourself, the name of the lab, and any other necessary identifying information.

Experiment 1Molecular Models of Neutral Molecules
Experiment Inventory

Materials
35 Toothpicks

Colored Pencils

*35 Marshmallows (Miniature)

*Permanent Marker

*Camera (camera phone is fine)

Labware
Protractor

Note: You must provide the materials listed in *red.

EXPERIMENT 1: MOLECULAR MODELS OF NEUTRAL MOLECULES

In this experiment, you will predict the three-dimensional geometry of a series of neutral molecules using the VSEPR theory.

PROCEDURE

Part 1: The Periodic Table

1. Use the Periodic Table of Elements to determine the elemental symbol, group number, and valence electrons for the
elements listed in Table 1 on the Experiment 1 Data Sheet. Record this data in Table 1.

2. Use colored pencils and the data in Table 1 to sketch a Lewis Dot Structure for each element in Table 1 on the Data Sheet.

©2018, eScience Labs

Part 2: Construction of Molecules

1. Now, construct the three-dimensional geometry for the molecules listed in Table 2 on the Data Sheet. While you are
constructing your molecules, keep the following points in mind:

• Nature “loves” symmetry, which means equal bond lengths and angles.

• Electrons prefer to be as far apart from each other as possible without disrupting the symmetry too drastically.

• Lone pairs take up more space because they are not confined by bonds, and are localized.

2. Look at Table 2 on the Data Sheet, and fill in the bond angles for each molecule you will be building.

Hint: Use the column in Table 2 on the Data Sheet labeled “Structure” to determine the molecular
geometry.

3. Using colored pencils, make a Lewis Dot Structure sketch for each molecule in Table 2 you will be building.

4. Gather as many marshmallows and toothpicks you will need for building your first molecule (carbon dioxide).

Hint: You will need two marshmallows for the oxygen (O), and one marshmallow for the carbon (C).

5. Using the permanent marker, label the miniature marshmallow
with the elemental symbol for each atom in your molecule
(Figure 19).

6. Refer to the first column in Table 2 to determine the central
atom in your molecule.

7. Connect the atoms together with toothpicks.

8. Compare your model with the diagram of the Linear molecular
geometry in Table 2.

9. Use your protractor to verify that you have constructed your
molecule with the correct bond angles.

10. To determine the angle between your atoms, place the center
of the protractor on the central atom, and align the base with a bond (Figure 19). Then measure the angle. When in
doubt, think “Should this angle be bigger or smaller than 90°?”

11. If your bond angles are incorrect, remove the toothpicks from the marshmallows, construct the molecule again, and use
your protractor to verify that you have constructed your molecule with the correct bond angles.

12. Follow the above procedures for each molecule in Table 2.

13. When you are finished, take a picture of the molecules and send the images to your instructor. Make sure you identify
yourself, the name of the lab, and any other necessary identifying information.

Figure 19: To satisfy the octet rule, the linear carbon dioxide molecule
has double bonds. Note, the bond angles should be 180 degrees.

©2018, eScience Labs

Data Sheet Experiment 1 Data Sheet
Table 1: Lewis Dot Structures

Element Symbol Group Number Valence Electrons Lewis Dot Structure

Hydrogen

Carbon

Chlorine

Aluminum

Oxygen

Fluorine

Neon

Nitrogen

©2018, eScience Labs

Data Sheet Experiment 1 Data Sheet
Table 2: Molecular Models

Molecule (central
atom is underlined)

Sketch of Lewis
Dot Structure

Shape Name Structure Bond Angle

CO2 Linear

AlCl3 Trigonal Planar

H2O Bent

NH3 Trigonal Pyramidal

..
N

H

H

H

CCl4 Tetrahedral
C

Cl

Cl
Cl

Cl

PCl5 Trigonal Bipyramidal P
Cl

Cl
Cl
Cl
Cl

SF6 Octahedral S

F

F

FF
FF

©2018, eScience Labs