Vsepr Theory & Hybridization Cont. Wood County Schools

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VSEPR T
& h
hEoRy
ybRidizaTion
Study Guides
Big Picture
Lewis structures are two-dimensional diagrams, but molecules are actually three-dimensional. The VSEPR (Valence
Shell Electron Pair Repulsion) theory allows us to visualize a molecule’s shape and the relative locations of a molecule’s
electrons. The size, shape, and orientation of these electron orbitals play an important role in an atom’s bonding
patterns. Orbital hybridization and molecular orbitals explain the nature of these orbitals.
Key Terms
Steric Number: The number of atoms bonded to the central atom plus the number of lone pairs.
Hybridization: When two or more orbitals “mix” to form two or more orbitals of an “average” size and energy.
sp-hybridized orbital: One of two orbitals created by hybridizing one s orbital with one p orbitals, producing two
orbitals at 180° degrees apart. Atoms forming two double bonds will hybridize in this fashion, leaving two un-
hybridized p orbitals.
sp
-hybridized orbital: One of three orbitals created by hybridizing one s orbital with two p orbitals, producing
2
3 orbitals at 120° degrees apart. Atoms forming one double bond will hybridize in this fashion (leaving one
un-hybridized p orbital).
sp
-hybridized orbital: One of four orbitals created by hybridizing one s orbital with three p orbitals, producing 4
3
orbitals at 109.5° degrees apart. Most atoms forming only single bonds will form this type of orbital.
sp
d-hybridized orbital: One of five orbitals created by hybridizing one s orbital, 3 p orbitals, and 1 d orbital,
3
producing three orbitals 120° degrees apart and two more orbitals 180° degrees apart on the vertical.
sp
3
d
2
-hybridized orbital: One of six orbitals created by hybridizing one s orbital, 3 p orbitals, and 2 d orbitals,
creating 6 orbitals 90° degrees apart.
Sigma Bond: A chemical bond involving s orbitals, p orbitals, or hybridized orbitals.
Pi Bond: A chemical bond involving un-hybridized p orbitals.
Molecular Geometry
The VSEPR theory helps to predict the molecular geometry. In VSEPR theory, the valence-electron pairs move as far
away from each other as possible in order to minimize repulsion between electron pairs (see table below).
The geometry is determined by the steric number.
A lone pair repels more strongly than paired electrons.
sp
sp
2
sp
3
sp
3
d
sp
3
d
2
This guide was created by Steven Lai, Rory Runser, and Jin Yu. To learn more
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about the student authors, visit
v1.1.12.2012
interns.

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