Shapes of Molecules Worksheet

Name _______________________Date __________
Shapes of Molecules
In this laboratory you will use the wooden balls and sticks to construct models of the molecules listed
below. While it is possible to find the answers in your book or on-line, the object of this laboratory is
not to get the answers, but to understand the structures. You will get this understanding by building
these structures and then examining them. Molecules are really three dimensional, even the very best
drawing can only approximate a real three dimensional structure.
Pre-Lab Questions:
In this exercise we will consider only molecules where the central atom has not more than 4 pairs
of electrons. The electron pairs below are on the surface of the central atom. You should enter the name
of the shape. The spaces with the line are to be left blank, because molecules with these characteristics
do not exist.
Number of electron domains
Two
Three
Four
Electron domain geometry
Molecular geometry with no
lone pairs
Molecular geometry with one
lone pair.
__________
Molecular geometry with two
lone pairs.
_________
_________
1. Define isomer and give a specific example.
2. Define resonance and give a specific example.
3. What conditions must exist for a molecule to be polar? Give a specific example.
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Shapes of Molecules
Green=F; Yellow=H; Red=O; Black=C; Purple=Br; Blue= N/S
Procedure:
1) Draw the Lewis Structure
2) Build the model of the molecule. Use springs for the double / triple bonds. Your Lewis structure
must be consistent with your model. If you can’t make the molecule using the model kit, then it
probably is not one! When there are more than two central atoms, the questions above refer to the
underlined atom or to the first carbon atom in the structure as you drew it.
3) Sketch the molecule that you created (as best you can). Try to indicate the three-dimensionality and
shape of it.
4) Determine the electron domain geometry
5) Determine the molecular geometry around the indicated atom.
6) Examine the sketch/model to determine whether the molecule is polar or non-polar. Draw in bond
dipoles in the sketch to see if they cancel each other out. Explain your answer in Analysis Question #1.
7) Try rearranging the atoms in your molecule. Is it possible to form isomers of the original compound?
If so, draw Lewis Structures for each isomer in Analysis Question #2.
8) If your compound has a double bond, can you change the location of that bond? Or in other words
does the molecule show resonance? Is so, draw the the resonance structures in Analysis Question #3.
Data Sheet:
Lewis Structure
Sketch w/ bond dipoles
CH4
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________ *
*Please explain in Analysis Question #1 now.
Isomers? ___________ **
** If “yes” go to Analysis question #2 now.
Resonance? __________***
*** If “yes” go to Analysis question #3 now.
Lewis Structure
Sketch w/ bond dipoles
CH3F
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
2
Lewis Structure
Sketch w/ bond dipoles
CH3OH
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
H2O
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
NH3
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar ? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
HF
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar ? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
H2O2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
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Lewis Structure
Sketch w/ bond dipoles
CO3-2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? __N/A (ionic)__
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
CO2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
C2H4
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
C2H2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
C2H2F2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
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Lewis Structure
Sketch w/ bond dipoles
SO2
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
Use a black sphere for S in this case.
SO3
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
HNO3
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
H2CO3
Electron domain geometry _________
Molecular geometry ___________
Polar or non-polar? __N/A (ionic___
Isomers? ___________**
Resonance? __________***
Lewis Structure
Sketch w/ bond dipoles
CH3COOElectron pair geometry _________
Molecular geometry ___________
Polar or non-polar? __N/A (ionic)__
Isomers? ___________**
Resonance? __________***
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Lewis Structure
Sketch w/ bond dipoles
C2H6O
Electron pair geometry _________
Molecular geometry ___________
Polar or non-polar? ____________*
Isomers? ___________**
Resonance? __________***
Analysis Questions:
1) For each Lewis structure you drew above, explain your choice of polar / nonpolar:
Molecule
Brief explanation of why you chose polar or nonpolar
CH4
CH3F
CH3OH
H2O
NH3
HF
H2O2
CO2
C2H4
C2H2
C2H2F2
SO2
SO3
HNO3
H2CO3
C2H6O
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2) For the molecules you answered “yes” to isomers, draw the Lewis Structure for each isomer and
determine whether or not the isomer(s) is polar or nonpolar.
3) For the molecules/ions you answered “yes” to resonance, draw all resonance structures for each
molecule.
Is there a “best” resonance structure for this ion or molecule?? Explain.
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