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Chapter 10.7 and 11.3-11.4

CHEM 112 Chapter Notes - Chapter 10.7 and 11.3-11.4: Trigonal Bipyramidal Molecular Geometry, Trigonal Planar Molecular Geometry, Chemical Polarity


Department
Chemistry
Course Code
CHEM 112
Professor
Gang Wu
Chapter
10.7 and 11.3-11.4

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Chemistry Week 6
10-7
The lewis structure for water gives the impression that the constituent atoms are arranged in a straight line
However the molecule is not linear, it is bent
To have a complete description of the shape of a molecule, we must determine the bond lengths, distances between nuclei of bonded atoms and
the bond angles
All diatomic molecules are linear
Triatomic molecules can be angular, bent or v-shaped
VSEPR Theory
o The shape of a molecule is established by experiment or by a quantum mechanical calculation
o Electron pairs repel each other whether they are in chemical bonds or lone pairs, electron pairs assume orientations about an atom to
minimize repulsions
o The dash wedge symbolism
Ordinary lines are used to represent bonds that lie in the plane of the paper
Solid wedges are used to represent bonds that point toward the viewer,
in front of the plane of the paper
Dashed wedges are used to represent bonds that point away from the
viewer, behind the plane of the paper
o The geometric distribution of electron groups is the electron-group geometry
o The geometric arrangement of atomic nuclei (the actual determinant of molecular
shape) is the molecular geometry
o VSEPR notation
A represents a central atom
X represents a terminal atom
E- represents a lone pair
Possibilities for electron-group distributions
o Electron group geometry
Two electron groups linear
Three electron groups trigonal planar
Four electron groups tetrahedral
Five electron groups trigonal bipyramidal
Six electron groups octahedral
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