Chapter 1: Chemical Bonding

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Chapter 1 Chemical Bonding
Aspartame (Nutrasweet)
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I. Electronic Configurations of the Elements
Periodic Table Review periods principle quantum
numbers s-block, p-block, d-block groups s and
p atomic orbitals rules for filling atomic
orbitals core and valence electrons Question
1-1. From a periodic table, give the electron
configuration and Lewis structure for the
following atoms. Then click on the arrow to
check your answers. C N O F Cl
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I. Electronic Configurations of the Elements
Answer 1-1 Electron Configuration Lewis
Symbol C He2s22p2 N He2s22p3 O
He2s22p4 F He2s22p5 Cl Ne2s22p5
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II. Bonding and Molecular Structure
A. Ionic, covalent, and polar bonds
electronegativity
ionic bonds transfer of electrons
covalent bonds sharing of electrons
electronegativity, ? relative attraction for
electrons in a bond - increases going up and to
the right in the periodic table - Pauling
electronegativity scale (arbitrary) Table 1.2
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II. Bonding and Molecular Structure
A. Ionic, covalent, and polar bonds
electronegativity
HH C 2.1 2.1 DC 0 ? equal sharing of
electrons ClCl nonpolar covalent bond C
3.0 3.0 HCl DC 0.9 ? unequal sharing of
electrons C 2.1 3.0 polar covalent
bond NaCl DC 2.1 ? transfer of
electrons C 0.9 3.0 ionic
bond generally when DC covalent 1.9 ? ionic
nonmetal nonmetal
d d
metal nonmetal
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Question 1-2. Use a periodic table or use the
Pauling electronegativity values to classify each
of the following compounds as non-polar
covalent, polar covalent, or ionic. Click on the
arrow to check your answers.
F2 H2
HF NaF
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Answer 1-2. Compare your answers
F2 H2
HF NaF
Non-polar covalent Non-polar covalent Polar
covalent Ionic
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II. Bonding and Molecular Structure
B. Drawing Lewis structures
1. Count all the valence electrons add one for
each charge subtract one for each
charge 2. Draw single bonds between the atoms
(the connectivity of the atoms is determined
experimentally and is usually given in the
problem). 3. Using the remaining valence
electrons, place octets on all atoms (exception
H), in order of decreasing electronegativity. 4.
If atoms do not have octets, use lone pair
electrons on adjacent atoms to form double or
triple bonds to complete the octets. 5. Determine
formal charges. 6. The better Lewis structure is
the one -with fewer formal charges -with more
octets -with a charge on a more
electronegative atom, and vice versa
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II. Bonding and Molecular Structure
B. Drawing Lewis structures Question 1-3. Draw
Lewis structures of the following.
CCl4 CH2O C2H2 CH3OH CH3CHCH2 HCN
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II. Bonding and Molecular Structure
B. Drawing Lewis structures Answer 1-3. Draw
Lewis structures of the following.
CCl4 CH2O
C2H2
CH3OH CH3CHCH2 HCN
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II. Bonding and Molecular Structure
C. Formal charges
(Use the silly, complex formula in the textbook,
or use this easier method.) 1. Divide the
electrons in each bond equally between the two
atoms sharing them. 2. Count the number of
electrons each atom now has and compare this
number to its normal valence. -more electrons
than normal valence ? negative formal
charge -fewer electrons than normal valence ?
positive formal charge Question 1-4. Draw the
Lewis structures, then determine the formal
charge on each atom in the following molecules or
ions. Check your answer by clicking on the
arrow. H3O CH3O CH3 CO N3
Check Answer
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II. Bonding and Molecular Structure
C. Formal charges
Answer 1-4. Compare your answers.
or
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II. Bonding and Molecular Structure
C. Formal charges
When two or more nonequivalent Lewis structures
are possible, the better (more stable) one is the
one with 1. fewer formal charges 2. more
octets 3. a charge on a more electronegative
atom,or a charge on a more electropositive
atom Question 1-5. Draw the most stable Lewis
structure for each of the following compounds.
Check your answers by clicking on the
arrow. COCl2 BF3 (CH3)2SO HOCN
In decreasing order of importance
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II. Bonding and Molecular Structure
C. Formal charges
Answer 1-4. The preferred Lewis structures are
shown here. Note that formal charges for all
atoms in the preferred Lewis structure are 0.
not
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II. Bonding and Molecular Structure
D. Structural formulas of organic compounds
structural formula condensed formula bond-line
formula
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II. Bonding and Molecular Structure
D. Structural formulas of organic compounds
Question 1-6. Draw the first two compounds in a
bond-line formula. Draw the second two compounds
in a condensed formula. Click on the arrow to
check your answer.
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II. Bonding and Molecular Structure
D. Structural formulas of organic compounds
Answer 1-6. Draw the first two compounds in a
bond-line formula. Draw the second two compounds
in a condensed formula. Click on the arrow to
check your answer.
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II. Bonding and Molecular Structure
E. Constitutional isomers -different atoms
bonded to one another different connectivity
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II. Bonding and Molecular Structure
E. Constitutional isomers
Question 1-8. Draw all of the constitutional
isomers for the following. Check your answer by
clicking on the arrow. C4H9Cl C3H6O
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II. Bonding and Molecular Structure
E. Constitutional isomers
Answer 1-8. There are four constitutional isomers
and five constitutional isomers,
respectively. C4H9Cl C3H6O
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II. Bonding and Molecular Structure
F. Resonance structures -atomic positions
(connectivity) the same, but different
arrangement of electrons
delocalized electrons

• neither of these accurately describes the formate
  ion
• actual species is an average of the two

• greater number of equivalent resonance structures
  ? greater stability
• resonance stabilization

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II. Bonding and Molecular Structure
F. Resonance structures Question 1-8. Draw
resonance forms for the following. Indicate
whether the resonance forms are equivalent in
energy. If not, indicate the major resonance
contributor (most stable). Click on the arrow to
check your answers.
SCN- CH2N2 CH3CO2-
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II. Bonding and Molecular Structure
F. Resonance structures Answer 1-8. The major
resonance forms are marked. Formal charge is
indicated above the structure.
SCN-
More electronegative atom has negative charge.
CH2N2
More electronegative atom has negative charge.
CH3CO2-
equal in stability
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II. Bonding and Molecular Structure
G. Molecular geometry Question 1-9. Draw Lewis
structures and determine molecular geometry for
each of the molecules. Click on the arrow to
check.
e pair
molecular formula
geometry geometry (angle) C2H2 CH2O C
H4 HCN NH3 H2O
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II. Bonding and Molecular Structure
G. Molecular geometry Answer 1-9. Draw Lewis
structures and determine molecular geometry for
each of the molecules. Click on the arrow to
check.
e pair
molecular formula Lewis geometry
geometry (angle) C2H2 CH2O CH4 HCN NH3
H2O
linear linear
(180) trigonal planar trigonal planar
(120) tetrahedral tetrahedral
(109.5) linear linear
(180) tetrahedral trigonal
pyramidal (107) tetrahedral bent
(104.5)
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II. Bonding and Molecular Structure
H. Molecular polarity Question 1-10. Draw the
Lewis structures, give the molecular geometry,
and determine whether the following will be polar
or non-polar. Click on the arrow to check your
answers.
CCl4 CHCl3 CH2O CO2
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II. Bonding and Molecular Structure
H. Molecular polarity Answer 1-10. Draw the
Lewis structures, give the molecular geometry,
and determine whether the following will be polar
or non-polar. Click on the arrow to check your
answers.
CCl4
CHCl3
net dipole polar
no net dipole non-polar
CO2
CH2O
net dipole polar
no net dipole non-polar
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III. Other Bonding Theories
A. Molecular orbital theory H2
H H ? HH
Two electrons in s1s are lower energy than in the
separate atoms ? covalent bond
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III. Other Bonding Theories
B. Valence bond theory
1. sp3 hybridization
tetrahedral, 4 equivalent bonds
CH4 facts
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III. Other Bonding Theories
B. Valence bond theory
1. sp3 hybridization
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III. Other Bonding Theories
B. Valence bond theory
trigonal planar sp2
2. sp2 hybridization
all six atoms lie in same plane
C2H4 facts
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III. Other Bonding Theories
B. Valence bond theory
2. sp2 hybridization
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III. Other Bonding Theories
B. Valence bond theory
3. sp hybridization
C2H2 facts
linear sp
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III. Other Bonding Theories
B. Valence bond theory
3. sp hybridization
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III. Other Bonding Theories
B. Valence bond theory
Question 1-11. What is the hybridization of each
indicated atom in the following compound? Click
on the arrow to check your answers.
17-ethynylestradiol (The Pill)
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III. Other Bonding Theories
B. Valence bond theory
Answer 1-11. What is the hybridization of each
indicated atom in the following compound? Click
on the arrow to check your answers.
sp
17-ethynylestradiol (The Pill)