Accel Chem
Covalent Bonding
Name:
Molecular Models Lab
Covalent bonding occurs when atoms share valence electrons. In the Valence Shell Electron Pair
Repulsion (VSEPR) theory, the way in which valence electrons of bonding atoms are positioned
is the basis for predicting a molecule’s shape. This method of visualizing shape is also based on
the molecule’s Lewis structure.
Guiding Question:
How do the Lewis structure and positions of valence electrons affect the shape and polarity of a
covalent molecule?
Materials:
Molecular Model Kit
Procedure:
1. Obtain a molecular model kit and write down the color code of atoms:
H:
O:
C:
Cl:
S:
N:
Note the different sized-connecters that you will use. Short connector = single bond.
Long connecter = double and triple bonds. Lone pairs of electrons are assumed on the models,
but they should be drawn in your Lewis structures.
2. Construct each of the following molecules. Complete the table by writing the formula,
structural diagram, shape, polarity of the bonds, and polarity of the molecule. You may use your
textbook or reference sheets for additional help.
Cl2; O2; N2; H2O; CO2; NH3; CCl4; CH2Cl2; SO3; HCN; CO; 3 additional examples of
your own choosing.
Analysis and conclusion:
Each person will respond to the following questions in pen (or typed) on a separate piece of
paper, and it is due on _______________. You will also attach your data table. These are
questions and reflections that pull many pieces from chemistry together and need to reflect your
best thinking.
1. Based on the molecular models you built and observed in this lab, rank single, double, and
triple bonds in order of increasing flexibility and in order of increasing strength.
Accel Chem
Covalent Bonding
Name:
2. What is meant by polar and nonpolar? Describe the difference thoroughly using the term
“electronegativity.”
3. What is VSEPR? How does it help us determine the shape of a molecule?
4. Explain why H2O and CO2 molecules have different shapes. Explain how their different
shapes affect the different polarities of the molecules.
5. Explain why methane (CH4) and dichloromethane (CH2Cl2) would have the same shape but
different polarities.
6. How do lone pairs of electrons on the central atom affect the polarity and shape of a
molecule?
7. One of the molecules from this lab undergoes resonance. Identify the molecule that has three
resonance structures, draw the structures, and explain why resonance occurs.
8. Look up additional information on Gilbert Lewis, the person whom Lewis structures are
named after. He led an interesting life, but unfortunately was never awarded the Nobel Prize for
his achievements. Write a couple paragraphs about his work and scientific achievements. Cite
your sources (www.google.com is not a source). The internet is not the only place you can
look…try a book!
Accel Chem
Covalent Bonding
Formula Lewis Dot Structure
Name:
VSEPR Shape
Are the bonds
Is the molecule
polar/nonpolar? polar/nonpolar?