Name _________________________________________ Block _____
Phet Molecule Shapes VSEPR Activity
Introduction
Since we write and draw in a two dimensional plane on paper, it is often difficult to visualize the true geometry/shape of
molecules. This activity and the program you are about to use allows you to view the molecules on a more 3dimensional scale.
Go to https://phet.colorado.edu/en/simulation/molecule-shapes or Google “phet simulations molecule shape.” Make
sure you are looking at the HTML 5 version. Click play.
Part 1
1. Click on Model. Take a moment to familiarize yourself with the screen. Notice you may add bonds and lone pairs of
electrons by clicking on those icons. Once you add a bond or lone pair you may click on the “X” to remove it.
Click on “Remove All” so the simulation may start with one atom. In the name box check “Molecule Geometry” and in
the options box check “Show Bond Angles”.
2. Add a single bond to the purple atom. Take your finger and drag it across the atom/bond you added. Notice how it
can be rotated. Draw the compound in the box.
How many atoms are in this compound?
What is the shape/geometry of this molecule?
# of bonds = _____________
# of lone pairs=_______________
Remove the single bond and add one double bond. How many atoms are in the compound? What is the shape?
Remove the double bond and add one triple bond. How many atoms are in the molecule? What is the shape?
3. Click “Remove All”. Add two single bonds to the purple atom. Next, add two lone pairs. Use your finger to spin the
molecule around. Draw the compound in the box.
How did the bond angle change when the lone pairs were added?
What is the shape/geometry of the molecule?
# of bonds = _____________
# of lone pairs=_______________
4. Click “Remove All”. Add three single bonds. Use your finger to spin the molecule around. Draw the compound in the
box.
Why do you think this shape is call trigonal planar? (HINT:
# of bonds = _____________
What does plane mean in math?)
# of lone pairs=_______________
5. Add one lone pair to your molecule. Use your finger to spin the molecule around. Draw the compound in the box.
What did the addition of the lone pair do to the bond angles?
What is the name of this shape?
# of bonds = _____________
# of lone pairs=_______________
6. Click “Remove All”. Add four single bonds to the purple central atom. Use your finger to spin the molecule around.
Draw the compound in the box.
What is the name of this shape?
# of bonds = _____________
# of lone pairs=_______________
7. Click “Remove All”. Add two double bonds to the purple central atom. Use your finger to spin the molecule around.
Draw the compound in the box.
What is the shape of this molecule?
# of bonds = _____________
# of lone pairs=_______________
Part 2
1. Click on “Real Molecules” on the bottom of the screen. Check “Molecule Geometry”.
H2O
2. Select “H2O”.
Which color represents oxygen? (look at the formula to help)
Which color represents hydrogen?
Which element is the central atom?
# of lone pairs
(on central atom)
# of bonds
(on central atom)
shape
3. Select “CO2”.
CO2
# of lone pairs
Which color represents oxygen? (look at the formula to help)
(on central atom)
Which color represents carbon?
(on central atom)
Which element is the central atom?
# of bonds
shape
4. Select “BF3”.
BF3
# of lone pairs
Which color represents boron? (look at the formula to help)
(on central atom)
Which color represents fluorine?
(on central atom)
Which element is the central atom?
# of bonds
shape
5. Select “NH3”.
NH3
# of lone pairs
Which color represents hydrogen? (look at the formula to help)
(on central atom)
Which color represents nitrogen?
(on central atom)
Which element is the central atom?
# of bonds
shape
6. Select “CH4”.
CH4
# of lone pairs
Which color represents carbon? (look at the formula to help)
(on central atom)
Which color represents hydrogen?
(on central atom)
Which element is the central atom?
# of bonds
shape
Analysis:
1. What geometry/shape does 1 single bond and no lone pairs produce?
2. What shape does 2 single bonds and 2 lone pairs produce?
3. What shape has 4 single bonds and no lone pairs?
4. What is the only shape that a molecule with only two atoms can produce?
5. Describe the difference between trigonal planar and trigonal pyramidal. Include a drawing for both.