The study of the three-dimensional shapes of molecules
Valence Shell Electron Pair Repulsion (VSEPR) Theory
can be used to predict molecular geometry, which in turn can be determined
from Lewis-dot diagrams of molecules and the arrangement of electron pairs
of the outermost (valence) electron energy level of the central atom.
Click on each shape diagram to view a
photo of a molecular model
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STEREOCHEMISTRY OF SOME COMMON MOLECULES
Compound
Lewis
Diagram
# of Lone Pairs Around
Central Atom
# of Bonding Electron Groups
Around Central Atom
Name of
Shape
*Shape Diagram and
Bond Dipoles
Polar
C2H2
H : C ::: C : H
0
2
linear
no
C2H4
0
3
trigonal
planar
no
CH4
0
4
tetrahedral
no
NH3
1
3
pyramidal
yes
H2O
2
2
v-shaped
(bent)
yes
*NOTE:
For the shape diagrams:
Solid lines represent bonds that are in the same
plane as that of the page
Dashed lines represent bonds that are directed into
the plane of the page
A wedge indicates bonds that are directed out
of the plane of the page
When determining the shapes of molecules the electron pairs of a multiple
bond count as a group since the bonds formed are all in the same direction
