Name: _________________________________
Date: _____________ Period: ____
Lab – Molecular Models
Introduction:
Lewis structures can be used to predict molecular and ionic geometries (shapes), as well as polarity.
Generally, atoms have eight electrons in their outer shell (octet rule). In addition, valence electrons exist in
electron domains around atoms in either bonded pairs or non-bonded (lone) pairs. These electron domains
can be used to predict the overall geometry of a molecule because electrons repel each other. This method is
termed valence-shell electron-pair repulsion (VSEPR) theory.
Materials: molecular models kits
Methods and Analysis:
Construct each of 12 molecular species, and then complete a data table including the following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Total valence electrons
Lewis structure
Total electron domains
Total lone pairs (nonbonded)
ABnEm category
Predicted molecular geometry (shape)
Predicted bond angle(s)
Symmetry (symmetrical or asymmetrical)
Polarity (yes or no)
Tips for Modeling Kit:
-Yellow wood spheres are H and any atom forming only one bond (like F, Cl, etc.).
-Red wood spheres are usually O (forms two bonds).
-Black wood spheres can be any atom with 4 domains (4 bonds) (3 bonds & 1 E pair) (2 bonds & 2 E pairs).
-Clay sphere is the central atom if exactly 3 domains are needed.
-Wood sticks are for single bonds (shared E pairs) and/or lone E pairs on the central atom only.
-Double or Triple Bonds are made with springs NOT wooden pegs.
1
Total
Lewis Structure:
Valence
Electrons:
H2 O
8
OR
Total
Molecular
Electron
Geometry
Domains: 4 (Shape):
# of Lone
Pairs: 2
ABmEn:
AB2E2
Total
Lewis Structure:
Valence
Electrons:
bent
Polar Molecule:
Bond Angle(s):
Total
Lewis Structure:
Valence
Electrons:
Molecular
Geometry
(Shape):
Total
Lewis Structure:
Valence
Electrons:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
# of Lone
Pairs:
ABmEn:
Symmetrical
or
Asymmetrical
Polar Molecule:
# of Lone
Pairs:
NH3
Yes or No
109.5o
# of Lone
Pairs:
HCN
CCl4
Total
Electron
Domains:
Symmetrical
or
Asymmetrical
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
Bond Angle(s):
Yes or No
2
CF2Cl2
Total
Lewis Structure:
Valence
Electrons:
Molecular
Geometry
(Shape):
# of Lone
Pairs:
(CFC
or
chlorofluorocarbon)
Total
Lewis Structure:
Valence
Electrons:
Total
Lewis Structure:
Valence
Electrons:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
Total
Lewis Structure:
Valence
Electrons:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
Symmetrical
or
Asymmetrical
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
# of Lone
Pairs:
ABmEn:
Yes or No
Polar Molecule:
# of Lone
Pairs:
H2S
Symmetrical
or
Asymmetrical
Polar Molecule:
# of Lone
Pairs:
BF3
HF
Total
Electron
Domains:
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
Bond Angle(s):
Yes or No
3
Total
Lewis Structure:
Valence
Electrons:
Total
Lewis Structure:
Valence
Electrons:
H
H
C
O
H
CH3OH
H
Total
Lewis Structure:
Valence
Electrons:
C2H6
Total
Lewis Structure:
Valence
Electrons:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
# of Lone
Pairs:
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
ABmEn:
Bond Angle(s):
Total
Electron
Domains:
Molecular
Geometry
(Shape):
# of Lone
Pairs:
ABmEn:
Symmetrical
or
Asymmetrical
Polar Molecule:
# of Lone
Pairs:
(two
central
atoms)
(two
central
atoms)
Molecular
Geometry
(Shape):
# of Lone
Pairs:
O2
C2H4
Total
Electron
Domains:
Yes or No
Symmetrical
or
Asymmetrical
Polar Molecule:
Bond Angle(s):
Yes or No
4