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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
Lewis Dot
Ionic vs. Molecular Compounds
Ionic Compounds
Metal + Non-Metal
Stealing of Electrons
Called Salts
Clumps of Ions
No prefixes, may need
Roman #
Lewis Dot
Molecules
Two Non-metals
Sharing of electrons
(Covalent or Polar Cov.)
Separate Molecules
Polar and Non-Polar
Molecules (H2O vs CH4)
Prefixes
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
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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Lewis Dot
L. Dot for Ionic Compounds
Lewis Dot
Why do Ionics steal? To gain an Octet
Draw Lewis Dot Pictures for:
NaCl
CaCl2
BaO
Li2O
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
Lewis Dot
Lewis Dot
Melting Point and Charge
MgCl2
(778 oC)
MgO
(2800 oC)
CaCl2
(772 oC)
CaO
(2528 oC)
Lewis Dot
Lewis Dot
Which would have a higher lattice energy?
Molecular Compounds
CH4
CO2
a. NaCl or KCl
b.CaBr2 or Ca3N2
c. NaCl or NaBr
d.CaI2 or CaO
H2O
Old School Lewis Dots
HCN
C2H4
C2H2
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Lewis Dot
Lewis Dot
Michael Faraday's Benzene Sample (1825)
Lewis Dot
Lewis Dot
Lewis Dots
Rules
The Lone
Pear(Pair)
rides again!
Lewis Dot
NH3
NCl3
SF6
CO2
HCN
ClF5
Lewis Dots
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
Lewis Dots
You try:
SF4
H2SO4
KrF4
Cl2O
NH2CH3
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CH3CH2CHCH2
Lewis Dots
Lewis Dots
CNICl4BrO3NO+
CHCCH2NCl2
Lewis Dot
Lewis Dots
Lewis Dot
Warm-Up:
You try:
CO32IBr4BF4SO42-
Examples
NO2-
Lewis Dot
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
Resonance
Structures
-
CHO2
Benzene
HNO3
Which needs resonance, SO3 or
SO32Order the species in the previous
problem from shortest to longest
bond length.
Resonance Structures
SO2
SO22-
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Lewis Dot
Less Than an Octet
• Hydrogen Only gets 2
• Beryllium, Boron, and Aluminum
BeCl2
BF3
AlF3
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Lewis Dot
More Than an Octet
• Just follow the rules and you
will be able to draw these
• Ex: AsF6-
Lewis Dot
Strengths of Covalent Bonds
Single < Double < Triple
Bond
C-C
C=C
C=C
N=N
Lewis Dot
Calculating Enthalpies of Reaction
Hrxn =
Hbroken –
made
Calculate the heat of reaction for the following
reaction.
CH4(g) + Cl2(g)  CH3Cl(g) + HCl(g)
Strength
(kJ/mole)
348
614
839
941
Bond Length
(Å)
1.54
1.34
1.20
1.10
Lewis Dot
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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Lewis Dot
Lewis Dot
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)
Lewis Dot
Lewis Dot
Calculate the H for the following reaction:
Bonds Broken
6 C-H
1 C-C
7/2 O2
Lewis Dot
Lewis Dot
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)]
Bonds Made
4 C=O
6 O-H
Calculate the H for the following reaction:
Hrxn = -1416 kJ (Exothermic reaction)
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Lewis Dot
Lewis Dot
Double Bonds
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)
Lewis Dot
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)
Lewis Dot
Double Bonds
Calculate the enthalpy change for the following
reaction.
If the enthalpy change for the following reaction is
0 kJ, calculate the C-Cl bond energy.
H H
| |
H-C=C-H + 2H2  H-C-C-H
| |
H H
(ANS: -289 kJ)
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)
Lewis Dot
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)
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IUPAC Names of Alkanes
Name the following and write the chemical formula
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
Lewis
Dot
16. BaF
CsCl
14. [Ca]2+2[F]- (8 ve- around F)
Li3N
Al2O3
2
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
2
Lewis
Dot 2 2
b) O has a double bond, shorter bond length
34. a) Draw LD of H O and O
2
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 < SO3
Lewis
Dot
2-
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.
Lewis
Dot
Lewis Dot
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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