6/13/2015 one point quiz one quiz per table, list everyone’s name agree on an answer you have...
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04/18/23
One Point Quiz
One quiz per table, list everyone’s name Agree on an answer You have two minutes
04/18/23
Formal Charge
The formal charge is the net charge on each atom.
Assume bonding electronsbelong 1/2 to each bonding atom.
HC
H
H O
H
• •• •
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Formal Charge
formalcharge
unsharedelectrons= e– donated - e– shared
2-
formal chargeof oxygen
6 valenceelectrons
=4/2 sharedelectrons
- -4 unsharedelectrons
HC
H
H O
H
• •• •
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• •• •
••C OHH
HH••••
• •• •
4 - 8/2 - 0 = 0
••••
• •• •
••••
• •• •
••
• •• •
••1 - 2/2 - 0 = 0
••
6 - 4/2 - 4 = 0
• •• •
•• ••
Formal Charges of AtomsMethanol
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
Atoms with low formal charges generally indicate thecorrect bonding pattern of chemically stable molecules.
04/18/23
Incorrect Diagrams for Methanol
••O• •
• •••••H
H• •
H
• •C HC: 4 - 6/2 - 2 = -1
H: 1 - 2/2 - 0 = 0
O: 6 - 6/2 - 2 = +1Validity Check
The sum of the formal charges always equalsthe charge on the molecule or ion.
HCH O
H
H
• •• •
C: 4 - 4/2 - 4 = -2
H: 1 - 2/2 - 0 = 0
O: 6 - 8/2 - 0 = +2
What are the formal charges for each atomin the following structures?
Validity CheckThe sum of the formal charges always equals
the charge on the molecule or ion.
04/18/23
Incorrect Diagrams for Methanol
••O• •
• •••••H
H• •
H
• •C H HCH O
H
H
• •• •
C: 4 - 4/2 - 4 = -2
H: 1 - 2/2 - 0 = 0
O: 6 - 8/2 - 0 = +2
C: 4 - 6/2 - 2 = -1
H: 1 - 2/2 - 0 = 0
O: 6 - 6/2 - 2 = +1
••O• •
• •••••H
H• •
H
• •C H
If either of these structures was stable,which one would more likely be stable?
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C N
Cyanide Ion
N 5 valence e–
total 10 valence e–
C 4 valence e–
5 e– pairs
Skeleton diagram
What are the formal charges for each atom in this ion?
C N•• ••••
charge 1 e–
•••• •• •••••• •• •••••• •••••• ••
Convert to aLewis Dot diagram
C: 4 - 6/2 - 2 = -1N: 5 - 6/2 - 2 = 0total charge = -1
Lewis Dot diagram
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Cyanide Ion
C: 4 - 6/2 - 2 = -1
N: 5 - 6/2 - 2 = 0total charge = -1
C N•• •••• ••••
Which “end” of cyanide ionis negative?
C N•• •••• ••••
Cyanide ion reacts with iron(III) ionto make the hexacyanoferrate(III) ion.
Does the iron(III) ion bond to carbon or nitrogen?
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Hexacyanoferrate(III) ion
FeC
N•• •••• ••
••CN••••••••
••
CN••••••••
••C
N •••• ••
••••
C
N
• •• •• •
• •• •
N
C•••• ••
••••
3-
Carbon is the negative end of the cyanide ion.
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Ammonium Ion
Nitrogen usuallyforms 3 bonds
NH H
H
H +
• • N 5 valence e–
total 8 valence e–
H 4 valence e–
charge -1 e–
Skeleton diagramLewis Dot diagram
4 e– pairs
••N• •
• •••H H
H
H +
H: 1 - 2/2 - 0 = 0
N: 5 - 8/2 - 0 = +1
total charge = +1
Which atoms have a non-zero formal charge?In an ion, some atom must have a non-zero formal charge.Why?
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Formal Charges
What are the formal charges on the atoms in• hydroxide ion• hydronium ion (oxonium ion)
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Chlorate Ion
Cl-O-O-O –
–
OO
O
Cl
Skeleton diagram
two possibilitiesusually the unique atom is in the center
chain structuresare uncommon
correctstructure
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Chlorate Ion
O 18 valence e–
total 26 valence e–
charge 1 e–
Cl 7 valence e–
Only 6 electronsshown
(3 pairs)
OO
O
Cl
Skeleton diagramLewis Dot diagram
13 e– pairs
••O
• •• •
••••O• •
• •••
••O
• •• •
••
• •Cl
Cl: 7 - 6/2 - 2 = +2
O: 6 - 2/2 - 6 = -1
total charge = -1
O: 6 - 2/2 - 6 = -1O: 6 - 2/2 - 6 = -1
Why is chlorate ion a good oxidizing agent?
Complete the Lewis Dot diagram
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Perchlorate Ion
O 24 valence e–
total 32 valence e–
charge 1 e–
Cl 7 valence e–
Only 8 electronsshown
(4 pairs)
OO Cl
OO
Skeleton diagramLewis Dot diagram
16 e– pairs
••O
• •• •
••••O• •
• •••
••O
• •• •
••
••O• •
• •••
Cl••Cl: 7 - 8/2 - 0 = +3
O: 6 - 2/2 - 6 = -1
total charge = -1
O: 6 - 2/2 - 6 = -1O: 6 - 2/2 - 6 = -1O: 6 - 2/2 - 6 = -1
Why areorganic perchlorate salts
potentially explosive?
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Pair ActivityFormal Charges
Develop a procedure to determine the formal charges on a molecule or ion.• Initially, one person should be responsible
for writing all the information. • The other person should be responsible for
saying what should be written.
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Pair ActivityFormal Charges
On a card or a piece of paper• write each sequential step necessary to
determine the formal charges.• number each step.• amend and update the list.
Determine the formal charges on
• acetic acid, CH3COOH
• acetate ion, CH3COO–
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Acetic Acid and Acetate Ion
O ••••
HCH
H
H
CO
••
••••
O ••••
••
O ••
••
CH
H
H
C
O ••••
CH
H
H
CO
••
••••
C: 4 - 8/2 - 0 = 0
total charge = 0
H: 1 - 2/2 - 0 = 0O: 6 - 4/2 - 4 = 0O: 6 - 4/2 - 4 = 0
C: 4 - 8/2 - 0 = 0
total charge = -1
H: 1 - 2/2 - 0 = 0O: 6 - 2/2 - 6 = -1O: 6 - 4/2 - 4 = 0
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Formal Charges
What are the formal charges on the atoms in• ozone• sulfite ion• sulfur trioxide
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“Connection” diagram
Convert to aLewis Dot diagram
Carbonate Ion
charge 2 e–
O 18 valence e–
total 24 valence e–
C 4 valence e–
OO
O
C
2-
O ••• •
••••O• •
• •••
••O
• •• •
••
••C
2-
Lewis Dot diagram
12 e– pairsWhich oxygen atomhas the double bond?