1. Lewis Dot Diagrams Edward A. Mottel Department of Chemistry
Rose-Hulman Institute of Technology

2. Bonding Theories Ionic Model Skeleton Diagrams
Identifies how atoms are linked together
Fails to describe the bonding in ions and certain molecules (e.g., CO, NH4+, CN–)
Fails to explain the geometry of molecules
Lewis Dot Diagrams
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3. Lewis Dot Diagrams 1s2 F H H F H F H F H F H F H F H F F H
Each dot represents an electron in the
outer (valence) shell in one of the atoms.
1s2 • F H • H F • H F • H F • H F
Each atom
attempts to attain
a stable outer shell
electronic configuration • H F • H F • H F
by sharing
electrons with
other atoms. • F H
(typically a noble gas electronic configuration)
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4. Didn’t your mother always tell you
to share?
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5. Lewis Dot Diagrams F H Each atom sharing an electron can count
that electron towards attaining its stable
electronic configuration.
isoelectronic
with helium
(DUET)
isoelectronic
with neon
(OCTET) • F H
Each pair of electrons which are shared
forms a bond between those atoms.
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6. Lewis Dot Diagrams
Bonding electrons may come from both atoms or they may only come from one atom.
The most stable bonding results when both atoms donate electrons to the bond.
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7. Carbon Monoxide Diagram
C 4 valence e–
eight electrons {
O 6 valence e– • O C • • • •
total valence e– {
eight electrons 10 8 2 6 4
Three pairs of electrons is a triple bond.
Both atoms are isoelectronic with neon.
C º O •
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8. Carbon Dioxide Diagram
eight
electrons { {
eight
electrons
C 4 valence e–
two O 12 valence e– • • • • C O
total valence e– • • {
eight
electrons 14 16 10 12 6 8 2 4
Carbon dioxide has two double bonds.
All three atoms are isoelectronic with neon. C O •
Draw the skeleton diagram for carbon dioxide.
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Determine the total number of valence e- available.

9. { { Ammonia Diagram eight electrons N 5 valence e–• N H
three H 3 valence e–
total valence e– {
two electrons
Nitrogen is isoelectronic with neon.
Each hydrogen is isoelectronic with helium.
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10. Carbon Tetrachloride Diagram
eight electrons {
C 4 valence e–
total valence e–
four Cl 28 valence e– • Cl C
eight electrons
Carbon is isoelectronic with neon.
Each chlorine is isolectronic with argon.
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11. Draw the Skeleton Diagram and Lewis Dot Diagram for Each of the Following
methane
dioxygen
ozone
water
hydrogen peroxide
ammonium ion
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12. Types of Bonds
The degree with which electrons are shared determines the type of bond that forms.
Covalent Bonds
Ionic Bonds
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13. Covalent Bonding
Results when each atom equally shares with the other atoms the electrons in its bonds.
One pair of shared electrons equals one bond.
Occurs with atoms of about the same electronegativity. C H
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14. Ionic Bonding Na Cl Results when "bonding" electrons are
transferred completely to one of the atoms.
Occurs with atoms of greatly different electronegativity. - + • Cl
atom with low
electronegativity
loses control
of the electron Na • • • •
atom with high
electronegativity
gains complete
control of the electron
isoelectronic
with argon
isoelectronic
with neon
Lewis Dot structures are more appropriate
for covalent bonding.
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15. Methanol methyl alcohol, wood alcohol, CH4O
Skeleton diagram
Lewis Dot diagram
C 4 valence e– H C O
H 4 valence e– •
O 6 valence e–
Lines or pairs of dots
can be used to
represent a bond.
total valence e–
How many electrons
are shown?
7 e– pairs
All valence electrons are represented as
bonds and nonbonding electrons
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16. Methanol methyl alcohol, wood alcohol, CH4O
Lewis Dot diagram
oxygen needs 8 e–
to complete its
outer shell • O H C
carbon needs
8 electrons to
complete its
outer shell of
electrons
(1s2 2s2 2p6)
each hydrogen only
needs 2 e– to complete
its outer shell (1s2)
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Next

17. Pair Activity Lewis Dot Structures
Develop a procedure to draw a Lewis Dot diagram.
Initially, one person should be responsible for writing all the information.
The other person should be responsible for saying what should be written.
Hint: Draw a valid skeleton diagram, and use that information to help draw the dot diagram.
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18. Lewis Dot Structures On a card or a piece of paper
write each sequential step necessary to draw a Lewis Dot diagram.
number each step.
amend and update the list. Either person may do this.
draw the Lewis Dot diagram of acetic acid, CH3COOH.
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19. Acetic Acid C • H O
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21. Formal Charge Edward A. Mottel Department of Chemistry
Rose-Hulman Institute of Technology

22. Formal Charge H C O Assume bonding electrons
belong 1/2 to each bonding atom. H C O •
The formal charge is the net charge on each atom.
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23. Formal Charge e– shared formal unshared = e– donated - - charge2
formal
charge
unshared
electrons
= e– donated - - H C O •
formal charge
of oxygen
6 valence
electrons
4/2 shared
electrons
4 unshared
electrons = - -
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24. Formal Charges of Atoms Methanol
4 - 8/2 - 0 = 0 • • C O H •
1 - 2/2 - 0 = 0
6 - 4/2 - 4 = 0 •
Atoms with low formal charges generally indicate the
correct bonding pattern of chemically stable molecules.
Formal charge =
valence electrons - electrons shared/2 - electrons not shared
C: 4 - 8/2 - 0 = 0
H: 1 - 2/2 - 0 = 0
O: 6 - 4/2 - 4 = 0
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25. Incorrect Diagrams for Methanol
What are the formal charges for each atom
in the following structures? • O H C H C O •
C: 4 - 6/2 - 2 = -1
H: 1 - 2/2 - 0 = 0
O: 6 - 6/2 - 2 = +1
C: 4 - 4/2 - 4 = -2
H: 1 - 2/2 - 0 = 0
O: 6 - 8/2 - 0 = +2
Validity Check
The sum of the formal charges always equals
the charge on the molecule or ion.
Validity Check
The sum of the formal charges always equals
the charge on the molecule or ion.
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26. Incorrect Diagrams for Methanol
If either of these structures was stable,
which one would more likely be stable? • O H C • O H C
C: 4 - 6/2 - 2 = -1
H: 1 - 2/2 - 0 = 0
O: 6 - 6/2 - 2 = +1
C: 4 - 4/2 - 4 = -2
H: 1 - 2/2 - 0 = 0
O: 6 - 8/2 - 0 = +2
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27. Cyanide Ion Lewis Dot diagram Skeleton diagram C 4 valence e–•
Lewis Dot diagram
Skeleton diagram
C 4 valence e– • • • C N • •
N 5 valence e–
charge 1 e–
total valence e–
C: 4 - 6/2 - 2 = -1
Convert to a
Lewis Dot diagram
N: 5 - 6/2 - 2 = 0
5 e– pairs
total charge = -1
What are the formal charges for each atom in this ion?
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28. Cyanide Ion C N C N • • Which “end” of cyanide ion is negative?
total charge = -1
Cyanide ion reacts with iron(III) ion
to make the hexacyanoferrate(III) ion.
Does the iron(III) ion bond to carbon or nitrogen?
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29. Hexacyanoferrate(III) ion• 3-
Carbon is the negative end of the cyanide ion.
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30. In an ion, some atom must have a non-zero formal charge.
Ammonium Ion
Lewis Dot diagram
Skeleton diagram • N H + N H + •
N 5 valence e–
total valence e–
H 4 valence e–
charge -1 e–
H: 1 - 2/2 - 0 = 0
N: 5 - 8/2 - 0 = +1
total charge = +1
Nitrogen usually
forms 3 bonds
4 e– pairs
In an ion, some atom must have a non-zero formal charge.
Why?
Which atoms have a non-zero formal charge?
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31. Formal Charges What are the formal charges on the atoms in
hydroxide ion
hydronium ion (oxonium ion)
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32. Chlorate Ion – Cl-O-O-O – Cl O Skeleton diagram
usually the unique atom is in the center
two possibilities – O Cl
Cl-O-O-O –
chain structures
are uncommon
correct
structure
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33. Chlorate Ion Lewis Dot diagram Skeleton diagram Cl 7 valence e–• O Cl O Cl
O 18 valence e–
charge 1 e–
total valence e–
Cl: 7 - 6/2 - 2 = +2
O: 6 - 2/2 - 6 = -1
total charge = -1
Only 6 electrons
shown
(3 pairs)
13 e– pairs
Complete the Lewis Dot diagram
Why is chlorate ion a good oxidizing agent?
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34. Perchlorate Ion Lewis Dot diagram Skeleton diagram O 24 valence e–
total valence e–
charge 1 e–
Cl 7 valence e– • O Cl O O O Cl O
Cl: 7 - 8/2 - 0 = +3
O: 6 - 2/2 - 6 = -1
total charge = -1
Only 8 electrons
shown
(4 pairs)
Why are
organic perchlorate salts
potentially explosive?
16 e– pairs
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