This lab is adapted from the T/TAC Online Community. This lab is in the Virginia SOL
Advanced Scope and Sequence.
Four at http://www.ttaconline.org/staff/sol/sol.asp and more specifically
http://www.ttaconline.org/staff/sol/sol_lessons.asp
This is actually what I would consider a lab for the gifted. The shapes that I have highlighted are
not required for the general chemistry student. Only the five simplest shapes of Linear, Bent,
Trigonal Planar, Trigonal Pyramidal, and Tetrahedral are required. For the general chemistry
student it is also taught that the noble gases to not make compounds so the advanced shapes are
not taught.
As a direct result of this I would give this version of the lab to my gifted students. I would take
out all of the highlighted material for the general regular ability students and give that lab to
them.
Molecular Model Building Lesson Plan
Organizing Topic Bonding, Nomenclature, and Formula Writing
Overview
Students use molecular model kits and draw Lewis dot diagrams to explore
molecular geometry and molecular polarity.
Related Standards of Learning
CH.1a, b, c; CH.3c, d
Objectives
The students will
 summarize the following concepts about covalent bonding:
o Covalent bonds involve sharing of electrons.
o Polar molecules result when a molecule behaves as if one end were positive and
the other negative.
o Electronegativity is the measure of attraction of an atom for electrons in a
covalent bond.
 draw Lewis dot diagrams to show covalent bonding;
 predict, draw, and name linear, bent, trigonal planar, tetrahedral, and trigonal pyramidal
molecular shapes;
 recognize polar and nonpolar molecules;
 understand and demonstrate
o MSDS warnings
o safety rules for science
o laboratory safety cautions
o safe techniques and procedures.
Prerequisite Understandings/Knowledge/Skills

The students need to be able to use the Periodic Table to determine the number of valence
electrons for a given element.
Materials needed

Molecular model kits (or toothpicks and small Styrofoam balls or gum drops)
Instructional activity
Content/Teacher Notes
In this activity, the student will gain valuable experience working with some hands-on molecular
models as they practice drawing Lewis dot structures and predict shapes according to the valence
shell electron pair repulsion rule (VSEPR).
You will need a classroom set of basic molecular model kits. Number each kit, and sign them out
by number; this will greatly reduce the loss of parts from one lab section to the next. If you do
not have access to molecular model kits, you can use toothpicks and gumdrops or small
Styrofoam balls, but the bond angles will be difficult to achieve.
Students who find the molecules in this lab easy to build can be assigned additional, advanced
molecules. Suggested advanced molecules and ions are listed below, grouped according to their
shape: (I would give these and other examples to my gifted students)
Linear
CO2
CS2
OCS
BeF2
+
−
NO2
NCF
SCN
OCN−
N2O
Tetrahedral arrangement
V-shaped (bent)
SCl2
SeBr2
BrO2−
ClO2−
OF2
Trigonal pyramidal
NF3
XeO3
SO32−
PO32−
SOCl2
−
−
PCl3
ClO3
IO3
Tetrahedral
SO42−
XeO4
PO43−
BF4−
CF4
−
4−
+
BrO4
SiF4
SiO4
NF4
AsCl4+
PF4+
SiCl4
ClO4
CCl4
NOF3
SO2Cl2
Trigonal bipyramidal arrangement
Linear
XeF2
KrF2
T-shaped
ClF3
BrF3
See-saw
SCl4
IO43−
Trigonal bipyramidal
SbF5
Octahedral arrangement
Square planar
IF4−
BrF4−
ClF2−
BrF2−
IF2−
IF3
XeOF2
XeF3+
XeO2F2
PF4−
AsCl4−
Square pyramidal
XeOF4
IF5
Octahedral
AlF63−
ClF5
BrF5
SeF5−
XeF5+
TeF5−
SbCl52−
ClOF4−
SiF62−
PF6−
IO65−
IF6+
Introduction
1.
Review with students the following basic points:

The properties of molecules depend not only on their molecular composition and
structure, but also on their shape. Molecular shape determines a compound’s state of
matter, boiling point, freezing point, viscosity, volatility, surface tension, and the
nature of its reactions.

The geometry of a small molecule can be predicted by examining the central atom
and identifying the number of atoms bonded to it and the number of unshared electron
pairs surrounding it.

The shapes of molecules may be predicted by using the VSEPR rule, which states that
electron pairs around a central atom will position themselves to allow for the
maximum amount of space between them.

Covalent bonds can be classified as either polar covalent or nonpolar covalent. In a
polar covalent bond, electrons are more attracted to the atom with the greater
electronegativity, resulting in a partial negative charge on that atom. The atom with
the smaller electronegativity value acquires a partial positive charge. In a nonpolar
covalent bond, the electrons are shared equally, and there is no unequal distribution
of charge.

Molecules made up of covalently bonded atoms can be classified as either polar or
nonpolar. The geometry of the molecule determines whether it is polar or not. For
example, if polar bonds are symmetrically arranged around a central atom, their
charges may cancel each other out and the molecule is nonpolar. If, on the other hand,
the arrangement of the polar bonds is asymmetrical, the electrons will be attracted
more to one end of the molecule and a polar molecule or dipole results.
2.
Tell students that in this activity, they will construct ball-and-stick models of covalent
molecules and name the geometry and the polarity of each molecule.
Procedure
1.
2.
Distribute molecular model kits (or toothpicks and small Styrofoam balls or gum drops) to
each team of students. Provide each group with enough parts to build several models before
having to take them apart to build new ones.
Have students build models of assigned molecules by following these steps:

Sum all of the molecule’s valence electrons.

Place the central atom, which is usually the first atom except for H.

Arrange the remaining atoms around the central atom.

Arrange the electrons around the atoms to obey the octet rule for all elements except
H. (C, N, O, and F always obey the octet rule.)

Obey the duet rule for H.

Form single bonds if possible. (Form multiple bonds only if absolutely necessary.)

Elements in the third row or below on the periodic table can hold extra electrons if
they are the central atom. (They have d-orbitals that can hold the extra electrons).
Have each student draw Lewis dot diagrams for the following atoms or molecules:
N
S
CH4
H2
N2
Cl2
H2O
HCN
NH3
CO2
H2O2
O3
SO42−
BrF3
XeO4
H2Se
CO32−
ICl3
CH2Cl2
C2H2
C6H6
3.
4.
Answer the following assessment questions:
a. Draw the Lewis diagram for oxygen.
b. Draw the Lewis diagram for SF4.
c. How many lone pairs of electrons are on the sulfur atom in the sulfite ion, SO32− ?
d. Use the VSEPR theory to predict the molecular geometry of SO2.
e. Use the VSEPR theory to predict the molecular geometry of H2Se.
f. Use the VSEPR theory to predict the molecular geometry of NH4+.
g. What is the polarity of the water molecule? Explain your answer.
Follow-up/extension

Reinforce the concept of conservation of mass in a chemical reaction by doing the
following:

Have students build models of the compounds CH4 and O2.

Have students write and balance the equation for the reaction that occurs between
CH4 and O2 to form CO2 and H2O

Then, have students build the number of CH4 and O2 molecules that are present in the
balanced equation.

When these models are complete, have students “react” the methane and oxygen
models by breaking the bonds in the reactants and reforming the product molecules.
They should see that they still have the same number of atoms in the product
molecules that they had in the reactants.
Vocabulary

The students need to know the following: atom, molecule, electron, valence electron,
polar, nonpolar, covalent, bond, linear, bent , trigonal planar, tetrahedral, trigonal
pyramidal (the 5 molecular shapes required by the VA SOLs).
Specific options for differentiating this lesson
For this lesson I would change the following things to differentiate:
For students with dysgraphia and dyslexia: Use a simulation that I could look at over their
shoulder so they would not have to write anything down on paper. A suitable website would be
http://phet.colorado.edu/en/simulation/molecule-shapes. It is not exactly like the lab, but it just
enough examples and opportunities to “draw” and build molecules. Students get to see the bond
angles, and the lone pairs of electrons. There is a student instruction sheet that goes with the lab
(attached in addition to this paper) that I have modified for our learning purposes. This
instruction sheet would be available on my Blackboard site for students to download so they
could type and make the table directly on the computer. They would they be able to print out
and turn in the assignment. Since I think doing hands on manipulation of the ball and stick
models are still important to understanding shapes, after they were done with the simulation, they
should join the members of the class that are completing the un-simulation version to what
practice with the manipulation.
Students with Attention Deficit/ Hyperactivity Disorder: Since students that have attention
deficit/hyperactivity may have a hard time organizing their thoughts I would provide them with a
data table to record all of their data. It would look something like this but expanded to fit all of
the different molecules they are going to be building.
Name
Formula
Dot Diagram
Hydrogen Gas
H2
H-H
3D
Representation
H-H
Molecular
Geometry
Linear
Molecular
Polarity
Nonpolar
For students that may have an issue visualizing the abstract concept of dot diagrams (this
can be any student): To draw the dot diagrams, students are able to use bingo chips in different
colors to represent the electrons around different elements. A bond is formed when the two
colors meet up in between the two atoms. I have found in the past that those students that use
this method end up understanding the concept of bonding better than they did before because
then can actually see the electrons moving and creating the bond through the manipulation of the
bingo chips.
Students with Asperger’s Syndrome: If the student would prefer, he or she could do the
computer simulation mentioned above. However, since I would like to encourage peer
communication, I would have the student work in a lab group with other students. I would keep
my eye of the student to make sure that students are not 1) making fun of the student, 2) being
patient and allowing for all students to be able to make the models, and 3) checking to make sure
that there is proper communication between the student and the other group members. I would
also give the student a table that was premade for them as given above. I want to encourage any
student with Asperger’s to work in social situations but, depending on severity, I would closely
monitor that group.
Structure and Polarity of
Molecules Lab
Introduction
The purpose of this lab is to evaluate the geometries and polarities of simple covalent molecules.
Many physical and chemical properties of compounds depend upon the shape or geometry of the
molecule and its polarity. A hemoglobin molecule, for example, becomes ineffective as an
oxygen transport vehicle if its shape is altered. Molecular shape determines a compound’s
boiling point, freezing point, and viscosity. A molecule’s polarity determines whether it
dissolves in water or not.
Molecular Geometries
The geometry of a small molecule can be predicted by examining the central atom. The valence
electron pairs that surround the central atom will repel each other. The electron pairs will
position themselves so that there is a maximum distance between them. This rule is called the
VSEPR theory. (Valence Shell Electron Pair Repulsion) The electron pairs include the covalent
bonds (shared pairs) and the unshared pairs of electrons.
Molecular Geometry Charts
Basic Shapes
Total # of e−
pairs
2
3
3
4
# of bonding
pairs
2
3
2
4
# of lone e−
pairs
0
0
1
0
4
3
1
4
4
2
1
2
3
Molecular
geometry
Linear
Trigonal planar
Bent
Tetrahedral
Trigonal
pyramidal
Bent
Linear
Bond
angles
180
120
<120
109.5
<109.5
<109.5
180
More Advanced Shapes
Total # of e−
pairs
# of bonding
pairs
# of lone e−
pairs
5
5
0
5
4
1
5
5
6
6
6
6
6
3
2
6
5
4
3
2
2
3
0
1
2
3
4
Molecular
geometry
Trigonal
bipyramidal
Bond
angles
90, 120
180, 90,
<120
T-shaped
90
Linear
180
Octahedral
90
Square pyramidal <90
Square planar
90
T-shaped
90
Linear
180
See-saw
Molecular Polarity:
Covalent molecules can be classified as polar or nonpolar. A polar molecule contains polar
covalent bonds that are asymmetrically arranged. This lack of symmetry causes an uneven
electron distribution around the central atom that leaves part of the molecule with a more
negative region, and part of the molecule with a more positive region. Remember that polar
bonds are covalent bonds between 2 atoms that have different electronegativities. (In the 0.5 to
1.9 range.)
Model Kits:
The model kits are used to demonstrate the shapes of small molecules. They are useful because they represent the
molecules in three dimensions, as opposed to two-dimensional drawings. The different colored balls represent
certain atoms, according to the chart:
Color
Element
Black
Yellow
Red
Blue
Carbon
Hydrogen
Oxygen
Nitrogen or Phosphorous
Orange
Bromine
Green
Purple
Chlorine
Iodine
# of holes
4
1
2
3 or 5
1
1
1
The smaller springs are used to represent single covalent bonds. The larger springs are used to
represent a double bond (2 springs used between two atoms) or a triple bond (2 springs used
between two atoms.
Procedure:
Make a table that includes molecular name, molecular formula, Dot Diagram, 3-D
Representation of the molecule after you have made it, Molecular Shape (name), and
Molecular polarity for each molecule listed in the box.
To properly fill in the table with all of the necessary information and get the correct
shape and diagram do the following for each molecule:
1.
determine the total number of e− pairs
2.
draw the Lewis structure
3.
determine the number of bonding e− pairs
4.
determine the number of lone e− pairs
5.
state the shape of the molecule
6.
state whether the molecule is polar or nonpolar.
H2
N2
CO2
O2
CH4
HBr
H2O
NH3
C2H5OH
HCN
H2O2
SO3
SeBr2
PCl3
CF4
C2H2
CH3NH2
BCl3
−
XeOF4
Br3
SeF4
IF5
AsF5
XeF4
IF3
BH2−
COCl2
N2F2
C6H6
CH2O
CH3CH2CH2OCH2CH2CH3
CH3CHCHCH2CH2CH3
C6H12
Acetone
isopropyl alcohol
acetic acid
boric acid