Transcript Chemistry - Weird Science With Mrs. Niki

Chemistry 8.3
8.3
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8.3
Bonding Theories
This car is being painted by
a process called
electrostatic spray
painting. The negatively
charged droplets are
attracted to the auto body.
You will learn how
attractive and repulsive
forces influence the
shapes of molecules.
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8.3
Bonding Theories > Molecular Orbitals
Molecular Orbitals
How are atomic and molecular orbitals
related?
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8.3
Bonding Theories > Molecular Orbitals
When two atoms combine, the molecular orbital
model assumes that their atomic orbitals overlap
to produce molecular orbitals, or orbitals that
apply to the entire molecule.
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8.3
Bonding Theories > Molecular Orbitals
Just as an atomic orbital belongs to a
particular atom, a molecular orbital
belongs to a molecule as a whole.
A molecular orbital that can be occupied by two
electrons of a covalent bond is called a bonding
orbital.
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8.3
Bonding Theories > Molecular Orbitals
Sigma Bonds
When two atomic orbitals combine to form a
molecular orbital that is symmetrical around the
axis connecting two atomic nuclei, a sigma
bond is formed.
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8.3
Bonding Theories > Molecular Orbitals
A Sigma Bond
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8.3
Bonding Theories > Molecular Orbitals
When two fluorine atoms combine, the p orbitals
overlap to produce a bonding molecular orbital.
The F—F bond is a sigma bond.
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8.3
Bonding Theories > Molecular Orbitals
Pi Bonds
In a pi bond (symbolized by the Greek letter ),
the bonding electrons are most likely to be found
in sausage-shaped regions above and below the
bond axis of the bonded atoms.
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8.3
Bonding Theories > Molecular Orbitals
Pi-bonding Molecular Orbital
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8.3
Bonding Theories > VSEPR Theory
VSEPR Theory
How does VSEPR theory help predict
the shapes of molecules?
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8.3
Bonding Theories > VSEPR Theory
The hydrogens in a methane molecule are at
the four corners of a geometric solid. All of the
H—C—H angles are 109.5°, the tetrahedral
angle.
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8.3
Bonding Theories > VSEPR Theory
The valence-shell electron-pair repulsion theory,
or VSEPR theory, explains the threedimensional shape of methane.
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8.3
Bonding Theories > VSEPR Theory
According to VSEPR theory, the
repulsion between electron pairs
causes molecular shapes to adjust
so that the valence-electron pairs
stay as far apart as possible.
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8.3
Bonding Theories > VSEPR Theory
The measured H—N—H bond angle is only
107°.
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8.3
Bonding Theories > VSEPR Theory
The measured bond angle in water is about
105°.
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8.3
Bonding Theories > VSEPR Theory
The carbon dioxide molecule is linear.
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8.3
Bonding Theories > VSEPR Theory
Nine Possible Molecular Shapes
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8.3
Bonding Theories > Hybrid Orbitals
Hybrid Orbitals
In what ways is orbital hybridization
useful in describing molecules?
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8.3
Bonding Theories > Hybrid Orbitals
Orbital hybridization provides information
about both molecular bonding and
molecular shape.
In hybridization, several atomic orbitals mix
to form the same total number of equivalent
hybrid orbitals.
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8.3
Bonding Theories > Hybrid Orbitals
Hybridization Involving Single Bonds
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8.3
Bonding Theories > Hybrid Orbitals
Hybridization Involving Double Bonds
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8.3
Bonding Theories > Hybrid Orbitals
Hybridization Involving Triple Bonds
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Bonding Theories > Hybrid Orbitals
Simulation 7 Compare sp, sp2, and sp3
hybrid orbitals.
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8.3 Section Quiz.
Assess students’ understanding
of the concepts in Section 8.3.
Continue to:
-or-
Launch:
Section Quiz
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8.3 Section Quiz.
1. A molecular orbital belongs to a
a. specific atom.
b. molecule as a whole.
c. specific pair of atoms.
d. central atom.
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8.3 Section Quiz.
2. VSEPR theory enables prediction of 3dimensional molecular shape because the
valence electron pairs
a. are attracted to each other.
b. form molecules with only four possible
shapes.
c. stay as far apart as possible.
d. always form tetrahedral shapes.
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8.3 Section Quiz.
3. Orbital hybridization provides information
about
a. both molecular bonding and molecular
shape.
b. both molecular bonding and bond energy.
c. neither molecular bonding nor molecular
shape.
d. neither molecular bonding nor bond
energy.
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