Lewis Dot
Lewis Dot
Types of Bonds
A. Electronegativity - The ability of an atom to
attract electrons to itself in a bond
1. Periodic Trends (link to size)
Metals – Low Electronegativity
Non- Metals – High Electroneg
The smaller the atom, the higher the
electronegativity
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Ionic vs. Molecular Compounds
Ionic Compounds
Metal + Non-Metal
Stealing of Electrons
Called Salts
Clumps of Ions
No prefixes, may need
Roman #
Molecules
Two Non-metals
Sharing of electrons
(Covalent or Polar Cov.)
Separate Molecules
Polar and Non-Polar
Molecules (H2O vs CH4)
Prefixes
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Lewis Dot
Types of Bonds
3. Types of bonds
Electroneg. Difference
Ionic
>2
Polar Cov.
0.2 – 1.9
Covalent
<0.2
Example: Li - F
Lewis Dot
Which of the following form predominantly ionic,
covalent, or polar covalent bonds?
B-Cl
Na-F
C-Cl
P-H
P-Cl
O-H
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L. Dot for Ionic Compounds
Why do Ionics steal? To gain an Octet
Draw Lewis Dot Pictures for:
NaCl
CaCl2
BaO
Li2O
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Lattice Energy – Energy required to convert a mole
of an ionic solid to its gaseous ions
NaCl(s)  Na+(g) + Cl-(g)
• Increases as distance (d) decreases
• Increases with increasing charge (Q)
U = k Q1Q2
d
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Melting Point and Charge
MgCl2
(778 oC)
MgO
(2800 oC)
CaCl2
(772 oC)
CaO
(2528 oC)
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Which would have a higher lattice energy?
a. NaCl or KCl
b.CaBr2 or Ca3N2
c. NaCl or NaBr
d.CaI2 or CaO
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Old School Lewis Dots
Molecular Compounds
CH4
CO2
H2O
HCN
C2H4
C2H2
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Michael Faraday's Benzene Sample (1825)
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The Lone
Pear(Pair)
rides again!
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Lewis Dots
Rules
1. Sum all valence electrons, including
charges
2. Single Bonds
3. Outer atoms get an octet except H
4. Center gets rest even if it violates the octet
5. Double/triple bonds if center atom still
does not have an octet
Lewis Dot
NH3
NCl3
SF6
CO2
HCN
ClF5
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You try:
SF4
H2SO4
KrF4
Cl2O
NH2CH3
Lewis Dots
CH3CH2CHCH2
CHCCH2NCl2
Lewis Dots
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CNICl4BrO3NO+
Lewis Dots
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You try:
CO32IBr4BF4SO42-
Lewis Dots
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Warm-Up:
Resonance Structures
O3
Definition – When a molecule can exist in
more than one arrangement of electrons
1. Atoms remain static
2. Only the electrons move
Examples
NO2-
Resonance
Structures
-
CHO2
HNO3
Which needs resonance, SO3 or
SO32-
Order the species in the previous
problem from shortest to longest
bond length.
Benzene
SO2
SO22-
Resonance Structures
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Less Than an Octet
• Hydrogen Only gets 2
• Beryllium, Boron, and Aluminum
BeCl2
BF3
AlF3
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More Than an Octet
• Just follow the rules and you
will be able to draw these
• Ex: AsF6-
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Strengths of Covalent Bonds
Single < Double < Triple
Bond
C-C
C=C
C=C
N=N
Strength
(kJ/mole)
348
614
839
941
Bond Length
(Å)
1.54
1.34
1.20
1.10
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Calculating Enthalpies of Reaction
Hrxn =  Hbroken – made
Calculate the heat of reaction for the following
reaction.
CH4(g) + Cl2(g)  CH3Cl(g) + HCl(g)
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Let’s look at bonds broken and made
H-CH3 + Cl-Cl  Cl-CH3 + H-Cl
Bonds broken: One mol C-H, One mol Cl-Cl
Bonds made: One mol C-Cl, One mol H-Cl
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Hrxn =  Hbroken – made
Hrxn = [1(C-H) + 1(Cl-Cl)] – [1(C-Cl) + 1(H-Cl)]
Hrxn = [413 kJ + 242 kJ] – [328 kJ + 431 kJ]
Hrxn = -104 kJ (Exothermic reaction)
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Lewis Dot
Calculate the H for the following reaction:
Lewis Dot
Bonds Broken
6 C-H
1 C-C
7/2 O2
Bonds Made
4 C=O
6 O-H
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Hrxn =  Hbroken – made
Hrxn = [6C-H + 1C-C + 7/2O2] – [4C=O + 6O-H]
Hrxn = [6(413) + 1(348) + 7/2(495)]
– [4(799) + 6(463)]
Hrxn = -1416 kJ (Exothermic reaction)
Lewis Dot
Calculate the H for the following reaction:
Lewis Dot
Bonds Broken
Bonds Made
4 N-H
1 N=N
1 N-N
2 H-H
Hrxn =  Hbroken – made
Hrxn = [4N-H + 1 N-N] – [1 N=N + 2 H-H]
Hrxn = [4(391) + 1(163)] – [1(941) + 2(436)]
Hrxn = -86 kJ (Exothermic reaction)
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Double Bonds
Calculate the enthalpy change for the following
reaction. Be sure to always break the multiple
bond and remake a single C-C bond.
Br Br
| |
H-C=C-H + Br2  H-C-C-H
| |
| |
H H
H H
(ANS: -93 kJ)
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Double Bonds
Calculate the enthalpy change for the following
reaction.
H H
| |
H-C=C-H + 2H2  H-C-C-H
| |
H H
(ANS: -289 kJ)
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If the enthalpy change for the following reaction is
0 kJ, calculate the C-Cl bond energy.
CH3Cl(g) + H2O(g)  CH3OH(g) + HCl(g)
Bond energy
H-Cl
430 kJ/mol
C- O
360 kJ/mol
O-H
460 kJ/mol
(ANS: 330 kJ/mol)
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If the enthalpy change for the following reaction is
-1995 kJ, calculate the bond energy of C=O.
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
Bond energy
C-C
345 kJ/mol
C-H
415 kJ/mol
O2
495 kJ/mol
O-H
460 kJ/mol
(800 kJ)
Organic Naming
Suffix
Suffix
Class
Characteristic
-ane
Alkane
All single bonds
-ene
Alkene
Double bond(s)
-yne
Alkynes
Triple bond(s)
IUPAC Names of Alkanes
Suffix = -ane
# of C
atoms
Name & Formula
# of C
atoms
Name & Formula
1
Methane CH4
6
Hexane C6H14
2
Ethane C2H6
7
Heptane C7H16
3
Propane C3H8
8
Octane C8H18
4
Butane C4H10
9
Nonane C9H20
5
Pentane C5H12
10
Decane C10H22
Name the following and write the chemical formula
14. [Ca]2+2[F]- (8 ve- around F)
Lewis
Dot
16. BaF2
CsCl
Li3N
Al2O3
20 a) KF has a larger LE because F- is much smaller than
Clb) Na – Cl ~ 2.8 A
K-F ~ 2.7A
22. a) (i) Increases with charge (ii) decreases with d
b) KBr < NaF < MgO < ScN
24 a) Ca2+ is smaller than Ba2+, higher LE
b) NaCl is smallest pair, highest LE
c) BaO has highest charges, highest LE
34. a) Draw LD of H2O2 and O2
Lewis
Dot
b) O2 has a double bond, shorter bond length
38. a) O
b) Al c) Cl d) F
40. a) O-F < C-F < Be-F
b) S-Br < C-P < O-Cl
c) C-S < N-O < B-F
50.Bond Length SO2 < SO3 < SO32Lewis Dot
52. CO2 (no resonance needed)
54. Bond Length NO+ < NO2- <NO366. a) -104 kJ b) 20 kJ c) 5 kJ
68. a) -2023 kJ b) -1255 kJ
c) -192 kJ
70. a) -124 kJ b) -137 kJ
1. a) C2H3Cl3O2
b) Same
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62.
100. In2S (I) [Kr]5s24d10
InS (II) [Kr]5s14d10
In2S3 (III) [Kr]4d10
In(III) is smallest (least mutual electron repul)
In(III) has the highest lattice energy
102.a) C2H3Cl3O2
b) C2H3Cl3O2
c) Structure CCl3CH(OH)2
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