GRC Mini Grant Prototype
Storyboard #1
Lewis Structure and Molecular
Geometry
Lewis Structure and Molecular Geometry Outline
1.1 Structure and Geometry of Methane - build a 2D Lewis structure,
consider 3D representations, select the correct one, observe differences.
recording (slides 4-8)
1.2 Structure and Geometry of Ammonia - build a 2D Lewis structure,
consider 3D representations, select the correct one, observe differences.
recording (slides 9-13)
1.3 Structure and Geometry of Water - build a 2D Lewis structure,
consider 3D representations, select the correct one, observe differences.
recording (slides 14-18)
1.4 The Connection to Biology - roll over activity to consider the unique
properties of water resulting from its geometry/polarity. (slide 19)
Tracking Sheet
1.1_v1.ppt by rjh 7.2.08
1.1_v1.ppt by blg 7.11.08
Learning Goals
-To understand how to go from the Lewis structure to the shape of a
molecule, both based on electron pair geometry and molecular geometry.
- To understand the differences between representing a molecule in two
dimensional space and three dimensional space.
Barbara Gonzalez:
Suggestions for learning goals expressed in terms that are amenable to assessable outcomes.
After completing this module, the learner will be able to:
-Determine the electron pair or steric number geometry of a molecule from a Lewis structure representation.
-Determine the molecular or coordination
number geometry of a molecule from a Lewis structure representation.
-Compare and contrast two- and three-dimensional representations of molecules.
1.1.1
Here’s the formula for methane (CH4). Build a Lewis structure below
for the methane molecule. Begin by dragging the central atom from
the supply on the left to the stage in the middle.
atoms
C H
bonds
l
electrons
(stage)
.
pairs
..
Barbara Gonzalez:
“Another convention that chemists use to represent shared electrons is to use a line to
represent a bond. Edit your Lewis structure to conform to this convention.
Metadata
Where will students be asked to explain how they built their structure?
1.1.2
Now that you’ve built a methane molecule in two dimensional space,
let’s represent methane in three dimensional space. Below are two
possible 3-D representations of a central atom bonded to four other
atoms. Click start on each representation to explore the arrangement
of the bonds.
A
square planar
start >
Barbara Gonzalez:
Now that you have built a methane molecule in twodimensional space using a Lewis structure, let’s
represent methane in three-dimensional space. Below
are two possible three-dimensional representations of
the central atom bonded to four other atoms. Click
START on each representation to explore the
arrangements of the bonds in each of the
representations.
Do we need a message to students who only explore one
of the geometries to take a look at both of them?
B
tetrahedral
start >
1.1.3
Now that you have explored the two possible arrangements, select
which arrangement is the correct 3-D representation for methane by
dragging it to the stage.
A
square planar
stage
B
tetrahedral
Barbara Gonzalez:
Please explain why you selected this representation?
 Please explain, why did you select this representation?
1.1.4
Now that you have explored the two possible arrangements, select
which arrangement is the correct 3-D representation for methane by
dragging it to the stage.
A
square planar
stage
B
tetrahedral
Bonds are more stable when
they are as far apart in space
as possible. Have you really
considered three dimensional
space? Try again.
 Please explain, why did you select this representation?
1.1.5
Click start on example A to see a 3-D representation of methane,
considering only the electron pairs that surround the central atom.
Click start on example B to see a representation of methane,
considering only the atoms.
A
B
Electron pair geometry
atom geometry
start >
Barbara Gonzalez:
Click START on Box A to see a three-dimensional
representation of methane that depicts only the electron
pairs that surround the central atom. Click START on
Box B to see a three-dimensional representation of
methane that depicts only the bonding electron pairs
that surround the central atom.
start >
Notice that they are the same.
1.2.1
Here’s the formula for ammonia (NH3). Create a Lewis structure
below for the ammonia molecule. Begin by dragging the central atom
from the supply on the left to the stage in the middle.
atoms
N H
bonds
l
electrons
stage
.
pairs
..
Barbara Gonzalez:
“Another convention that chemists use to represent shared electrons is to use a line to
represent a bond. Edit your Lewis structure to conform to this convention.
Metadata
Where will students be asked to explain how they built their structure?
1.2.2
Now that you’ve built an ammonia molecule in two dimensional space, let’s represent
ammonia in three dimensional space. Below are five possible 3-D representations of a
central atom bonded to three other atoms. Click start on each representation to
explore the arrangement of the bonds.
A
D
T shaped
Square planar
start >
B
start >
Barbara Gonzalez:
Now that you have drawn a representation of an
ammonia molecule in two-dimensional space, how is the
ammonia molecule represented in three-dimensional
space? Below are five possible three-dimensional
representations of a central atom bonded to three other
atoms. Click START on each representation to explore
the arrangements of the bonds.
E
Trigonal planar
start >
C
Trigonal pyramidal
start >
Tetrahedral
start >
stage
1.2.3
Now that you have explored the possible arrangements, select which
arrangement is the correct 3-D molecular geometry for ammonia by dragging it to
the stage.
A
Barbara Gonzalez:
Now that you have explored the possible arrangements,
select which arrangement is the correct threedimensional geometry for ammonia by dragging it into
the stage.
D
T shaped
B
Trigonal planar
Square planar
E
stage
Tetrahedral
C
Trigonal pyramidal
 Please explain, why did you select this representation?
Barbara Gonzalez:
Please explain, why you selected this representation.
Now that you have explored the possible arrangements, select which
arrangement is the correct 3-D molecular geometry for ammonia by dragging it to
the stage.
1.2.4
A
Barbara Gonzalez:
Now that you have explored the possible arrangements,
select which arrangement is the correct threedimensional geometry for ammonia by dragging it into
the stage.
D
T shaped
B
Trigonal planar
C
Square planar
stage
E
Tetrahedral
Barbara Gonzalez;
Bonds are more stable when they are as far apart in
space as possible. Have you really considered
three dimensional space? Try again.
Bonds are more stable when
they are as far apart in space
as possible, have you really
considered three dimensional
space? Try again.
Trigonal pyramidal
 Please explain, why did you select this representation?
Barbara Gonzalez:
Please explain, why you selected this representation.
1.2.5
Click start on example A to see a 3-D representation of ammonia,
considering only the electron pairs that surround the central atom.
Click start on example B to see a representation of ammonia,
considering only the atoms.
Barbara Gonzalez:
Click START on Box A to see a three-dimensional representation of the ammonia molecule that depicts only the
electron pairs that surround the central atom.
A START on Box B to see a three-dimensional representation
B of the ammonia molecule that depicts only the
Click
bonding electron pairs that surround the central atom.
Electron pair geometry
atom geometry
start >
Notice that the two geometries are different.
The electron pair geometry considers all of the
regions of electron density and the molecular
geometry considers only the atoms bonded to the
central atom.
start >
1.3.1
Here’s the formula for water (H2O). Build a Lewis structure below for
the water molecule. Begin by dragging the central atom from the
supply on the left to the stage in the middle.
atoms
O H
bonds
l
electrons
stage
.
pairs
..
Barbara Gonzalez:
“Another convention that chemists use to represent shared electrons is to use a line to
represent a bond. Edit your Lewis structure to conform to this convention.
Now that you’ve built a water molecule in two dimensional space, let’s represent water
in three dimensional space. Below are four possible 3-D representations of a central
atom bonded to two other atoms. Click on each representation to explore the
arrangement of the bonds.
1.3.2
A
C
linear
B
bent
square planar
Barbara Gonzalez:
Now that you have drawn a representation of a water
molecule in two-dimensional space, how is the water
molecule represented in three-dimensional space?
Below are five possible three-dimensional
representations of a central atom bonded to two other
atoms. Click START on each representation to explore
the arrangements of the bonds.
D
tetrahedral
stage
1.3.3
Now that you have explored the possible arrangements, select which
arrangement is the correct 3-D molecular geometry for water by dragging it to the
stage.
A
C
linear
B
bent
square planar
Barbara Gonzalez:
Now that you have explored the possible arrangements,
select the correct three-dimensional representation for
the molecular geometry of water by dragging it to the
stage.
D
tetrahedral
stage
 Please explain, why did you select this representation?
Barbara Gonzalez:
Please explain why you selected this representation?
1.3.4
Now that you have explored the possible arrangements, select which
arrangement is the correct 3-D molecular geometry for water by dragging it to the
stage.
A
C
linear
B
bent
square planar
stage
D
tetrahedral
Bonds are more stable when
they are as far apart in space
as possible. Have you really
considered three dimensional
space? Try again.
 Please explain, why did you select this representation?
Barbara Gonzalez:
Please explain why you selected this representation?
1.3.5
Click start on example A to see a 3-D representation of water,
considering only the electron pairs that surround the central atom.
Click start on example B to see a representation of water, considering
only the atoms.
A
B
Electron pair geometry
atom geometry
start >
start >
Barbara Gonzalez:
Click START on Box A to see a three-dimensional representation of a water molecule that depicts only the
electron pairs that surround the central atom.
Click START on Box B to see a three-dimensional representation of a water molecule that depicts only the
bonding electron pairs that surround the central atom.
 Are these two geometries the same? Why or
why not?
1.4