CHEM 1111 Chapter Notes - Chapter 7: Trigonal Bipyramidal Molecular Geometry, Trigonal Planar Molecular Geometry, Valence Bond Theory
Chapter 7: Molecular Geometry,
Intermolecular Forces, and
Bonding Theories
7.1 Molecular Geometry
-valence-shell-electron-pair repulsion (VSEPR) model
•model that accounts for electron pairs in
the valence shell of an atom repelling one
another
•example: AB2 may be linear or bent
•example: AB3 may be planar, pyramidal of
T-shaped
The VSEPR Model
-basis of VSEPR model
•electron pairs in a valence shell of an atom repel one another
•refer to electron domains instead of electron pairs
-electron domain
•lone pair or bond, regardless of whether the bond is single, double or triple
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•model predicts that because these electron domains repel one another, they will arrange
themselves to be as far apart as possible, thus minimizing the repulsive interactions between
them
•Image displays the geometries of molecules: a) linear b) trigonal planar c) tetrahedral d)
trigonal bipyramidal and e) octahedral
Electron-Domain Geometry and Molecular Geometry
-electron-domain geometry
•arrangement of electron domains (bonds and lone pairs) around the central atom
-molecular geometry
•arrangement of bonded atoms
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-above image displays
ABx molecules in which
all the electron domains
are bonds—there are no
lone pairs on any of the
central atoms
•molecular geometry =
electron-domain
geometry
-bond angle
•angle between two
adjacent A—B bonds
-axial
•two bonds that form
an axis perpendicular
to the trigonal plane
-equatorial
•three bonds that are
arranged in a trigonal
plane
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find more resources at oneclass.com
Document Summary
Valence-shell-electron-pair repulsion (vsepr) model: model that accounts for electron pairs in the valence shell of an atom repelling one another, example: ab2 may be linear or bent, example: ab3 may be planar, pyramidal of. Basis of vsepr model: electron pairs in a valence shell of an atom repel one another, refer to electron domains instead of electron pairs. Electron-domain geometry: arrangement of electron domains (bonds and lone pairs) around the central atom. Molecular geometry: arrangement of bonded atoms. Abx molecules in which all the electron domains are bonds there are no lone pairs on any of the central atoms: molecular geometry = electron-domain geometry. Bond angle: angle between two adjacent a b bonds. Axial: two bonds that form an axis perpendicular to the trigonal plane. Equatorial: three bonds that are arranged in a trigonal plane. Molecular polarity: one of the most important consequences of molecular geometry, influences physical, chemical, and biological properties. Many molecules with polar bonds are nonpolar.
