IB Chemistry on Redox, Oxidation states, oxidation number

1. http://lawrencekok.blogspot.com
Prepared by
Lawrence Kok
Video Tutorial on Redox, Oxidation, Reduction and
oxidation number.

2. Cations/Metals/+ve ions
Gp 1 Gp 2 Gp 3 Transition metals ions
( variable oxidation states)
Oxidation
state
+1
Oxidation
state
+2
Oxidation
state
+3
Sc
+3
Ti
+2
+3
V
+2
+3
Cr
+2
+3
+6
Mn
+2
+3
+6
+7
Fe
+2
+3
Co
+2
+3
Ni
+2
Cu
+1
+2
Zn
+2
Li 1+
Be2+ Sc 3+
Ti 2+
Ti3+
V 2+
V 3+
Cr 2+
C r3+
Cr6+
Mn 2+
Mn 3+
Mn 6+
Mn 7+
Fe 2+
Fe 3+
Co2+
Co 3+
Ni2+
Cu1+
Cu2+
Zn2+
Na 1+
Mg2+ Al 3+
K1+
Ca2+
Anion/Non metal
Gp 5 Gp 6 Gp 7
Oxidation
state
Oxidation
state
Oxidation
state
-3 -2 -1
N3-
O2-
F-1
P3-
S2-
CI-1
Br-1
I-1
Metal/Cations/+ve ions
Non Metal/
Anions/
-ve ions
Ionic Compound
Li2O MgCI2 Al2O3 FeO
Iron(II) oxide
NiO
Nickel(II) oxide
CuO
Copper(II) oxide
Li3N Mg3N2 AlN Fe3N2
Iron(II) nitride
Ni3N2
Nickel(II) nitride
Cu3N2
Copper(II) nitride
Oxidation state/Charge ion → Li1+
O2-
Formula compound Li2
O1
Video on polyatomic ions
Writing Chemical Formula
Step 1 : Write Oxidation state/charge
Step 2 : Balance it, (electrically neutral)
by cross multiply – as subscript

3. Polyatomic ions
Group of non-metals bonded together
Oxidation
state
Oxidation
state
Oxidation
state
-1/+1 -2 -3
(OH)-1
Hydroxide
(SO4)2-
Sulphate
(PO4
)3-
Phosphate
(CN)-1
Cyanide
(SO3
)2-
Sulphite
(SCN)-1
Thiocyanate
(CO3
)2-
Carbonate
(NO3
)-1
Nitrate
(S2
O3
)2-
Thiosulphate
(NO2)-1
Nitrite
(Cr2O7)2-
Dichromate
(NH4
)+1
Ammonium
Polyatomic ions
Li2(CO3) Mg(CO3) Al2(CO3)3 Fe(CO3) Ni(CO3) Cu(CO3)
Li(OH) Mg(OH)2 Al(OH)3 Fe(OH)2 Ni(OH)2 Cu(OH)2
Li2(SO4) Mg(SO4) Al2(SO4)3 FeSO4 Ni(SO4) Cu(SO4) Video on polyatomic ions
Ionic Compound
Writing Chemical Formula
Metal/Cations/+ve ions
Cations/Metals/+ve ions
Gp1 Gp 2 Gp3 Transition metals ions
( variable oxidation states)
Oxidation
state
+1
Oxidation
state
+2
Oxidation
state
+3
Sc
+3
Ti
+2
+3
V
+2
+3
Cr
+2
+3
+6
Mn
+2
+3
+6
+7
Fe
+2
+3
Co
+2
+3
Ni
+2
Cu
+1
+2
Li 1+
Be2+ Sc 3+
Ti 2+
Ti3+
V 2+
V 3+
Cr 2+
C r3+
Cr6+
Mn 2+
Mn 3+
Mn 6+
Mn 7+
Fe 2+
Fe 3+
Co2+
Co3+
Ni2+
Cu1+
Cu2+
Na 1+
Mg2+ Al 3+
K1+
Ca2+
Oxidation state/Charge ion → Li1+
(CO3)2-
Formula compound Li2
(CO3
)1
Step 1 : Write Oxidation state/charge ion
Step 2 : Balance it, (electrically neutral)
by cross multiply – as subscript

4. Redox (Oxidation and Reduction)
Oxidation – Gain of oxygen ↑
Oxidation – Loss of hydrogen ↓ Reduction – Gain of hydrogen ↑
Reduction – Loss of oxygen ↓
Oxidation Reduction
Gain oxygen ↑ Loss oxygen ↓
Gain oxidation
Number ↑
Loss oxidation
Number ↓
Loss hydrogen ↓ Gain hydrogen ↑
Loss electron ↓ Gain electron ↑
Ca + O2 CaO→ CH4 + 2O2 CO→ 2+ 2H2O
gain oxygen gain oxygen
Zn + CuO ZnO + Cu→ PbO + CO Pb + CO→ 2
loss oxygen loss oxygen
H2S + CI2 S +2HCI→
loss hydrogen
H2S + CI2 S + 2HCI→
Redox- Oxidation state change
- Electron transfer
CH4 + 2O2 → CO2 + 2H2O
gain hydrogen
Zn + CuSO4 → ZnSO4 + Cu Zn + CI2 → ZnCI2
No gain/loss
oxygen/hydrogen
Redox
gain oxygen
gain hydrogen
Reduction
Oxidation
Are these redox rxns?

5. Redox- Oxidation state change
- Electron transfer
Zn + CuSO4 → ZnSO4 + Cu Zn + CI2 → ZnCI2No gain/loss
oxygen/hydrogen
Are these redox rxns?
Yes – change in oxidation number
Yes – loss/gain of electron
Yes – change in oxidation number
Yes – loss/gain of electron✓ ✓
• Assuming bond are ionic with diff EN values (unless bet same element)
• Assign each atom, measure of electron control relative to atom in pure element
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
• + means lose electron
• - means gain electron
Oxidation State/Number/ON Rules
Oxidation Reduction
Gain oxygen ↑ Loss oxygen ↓
Gain oxidation
Number ↑
Loss oxidation
Number ↓
Loss hydrogen ↓ Gain hydrogen ↑
Loss electron ↓ Gain electron ↑
H CI
xx
xx
•
x
∂-∂+
+1 -1Oxidation number
Oxidation state (sign, number) +2 NOT 2+
Oxidation state and formal charge useful tool for electron book- keeping. They are not REAL!
- Oxidation state -Assume bond ionic with diff EN values (unless bet same element)
- Formal charge – Assume bond covalent
Redox (Oxidation and Reduction)

6. Redox (Oxidation and Reduction)
• Assuming bond are ionic with diffEN values (unless bet same element)
• Assign each atom, measure of electron control relative to atom in pure element
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
• + means lose electron
• - means gain electron
Oxidation Number/ON Rules
H CI
xx
xx
•
x
∂-∂+
+1 -1Oxidation number
Oxidation state (sign, number) +2 NOT 2+
Oxidation state and formal charge useful tool for electron book- keeping. They are not REAL!
- Oxidation state -Assume bond ionic with diff EN values (unless bet same element)
- Formal charge – Assume bond covalent
xx
CI CI
Oxidation Number/ON Rules
H CI Na CI
Imagine electron move to more EN element
O C O
oo
o
o
xxoo
oo xx
xx
o
x
Equal sharing
xx
xx
xx
o
x
+1 -1
Unequal sharing
0 0
xx
xx
xx
o
x
+1 -1
Complete transfer
ox
ox
o
o
oo
oo
oo
oo
o
o
xo
xo
Unequal sharing
-2 +4 -2
H O H
CI2
H CI Na CI C O2
+1 -1 -1+1 +4 -2
oo
o
x
o
x
+1 -2 +1
Unequal sharing
H N H
H
o
x
o
x
o
x
oo
+1 -3 +1
+1
Unequal sharing
H2 O N H3
H C H
H
H
o
x
o
xo
x
o
x
+1
+1
+1
+1 -4
C H4
+1 -2 -3 +1 -4 +1
CI C CI
CI
CI
-1
-1
-1
-1
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
xx
xo
xo
ox
ox
+4
C CI4
+4 -1
0

7. Exceptions
Element ON Exception Example
Hydrogen +1
H +1
-1
Bond to metal
Metal hydride
NaH
CaH2
Oxidation Number/States/ON Rules Imagine electron move to more EN element
• Assuming bond are ionic with diff EN values (unless bet same element)
• Assign each atom, measure of electron control relative to atom in pure element
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
H CI
xx
∂-
xx
•
x
Oxidation number +1 -1
∂+
xx
H CI
xx
xx
xx
+1 -1
o
x
Unequal sharing
H CI
+1 -1
Na Ho
x
+1 -1
Complete transfer
Na H
+1 -1
Exceptions
Element ON Exception Example
Oxygen -2
O -2
+2
Bond to
fluorine
F2O
Exceptions
Element ON Exception Example
Oxygen -2
O-2
-1
Peroxide
(O-O)
H2O2
H O H F O F
oo
oo
o
x
o
x
+1 -2 +1
Unequal sharing
H2 O
+1 -2
oo
oo
xx
xx
xx
xx
xx
xx
ox
ox
-1 +2 -1
Unequal sharing
F2 O
-1 +2
O O HH
O-O single bond
oo
oo
oo
oo
ox
ox
o
o
equal sharing
+1 -1 -1 +1
Unequal sharing
H2 O2
+1 -1
EN fluorine higher ↑EN oxygen higher ↑
Oxidation Number/ON Rules Imagine electron move to more EN element
O O H O H
Oxidation state O different – depend element bond with – different EN values !
F O F O O
xx
xx
xx
xx
xx
xx
Equal sharing
0 0
O2
0
oo
oo
oo
oo
ox
ox
+1 -2 +1
Unequal sharing
H2 O
+1 -2
xx
xx
xx xx
xxxx
ox
ox
-1 +2 -1
F2 O
-1 +2
H H
oo
oo
oo
oo
o
o
ox
ox
+1 -1 -1 +1
H2 O2
+1 -1
Unequal sharing Unequal sharing

8. Oxidation Number/ON Rules Imagine electron move to more EN element
• Assuming bond are ionic with diff EN values (unless bet same element)
• Assign each atom, measure of electron control relative to atom in pure element
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
H CI
xx
∂-
xx
•
x
Oxidation number +1 -1
∂+
xx
Oxidation Number/ON Rules Imagine electron move to more EN element
O O H O H
Oxidation state O different – depend element bond with – different EN values !
F O F O O
xx
xx
xx
xx
xx
xx
Equal sharing
0 0
O2
0
oo
oo
oo
oo
ox
ox
+1 -2 +1
Unequal sharing
H2 O
+1 -2
xx
xx
xx xx
xxxx
ox
ox
-1 +2 -1
F2 O
-1 +2
H H
oo
oo
oo
oo
o
o
ox
ox
+1 -1 -1 +1
H2 O2
+1 -1
Unequal sharing Unequal sharing
Oxidation Number/ON Rules Imagine electron move to more EN element
Oxidation state N different – depend element bond with – different EN values !
H N H
H
H
H O N O H O N O N O N
O
O O
O
ox
ox
o x
x x
x x
+1 -3 +1
+1
-2
[N H4 ]
-3 +1 +1
Unequal sharing
xx
ox
ox
xo
xo
xx
oo
oo oo
oo
+1 -2 +3 -2
Unequal sharing
H N O2
+1 +3 -2
O
ox
ox
xo
xo
xx
oo
o
o
o
o
+1 -2 +5 -2
-2
Unequal sharing
H N O3
+1 +5 -2
ox
ox
xx
oo
xx
oo
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
oo oo -2
-2 -2
-5 -5-2
N2 O5
Unequal sharing
-5 +2
+1
+

9. Oxidation Number/ON Rules
Atoms uncombined free element state = ON = 0
Ion form – ON same as charged on ion
1
2
Mg
Mg2+
Na
Na+
O2 S8
O2-
3 ON for element same as its most common ion/group
ON metal from Gp 1 – 3
ON non metal Gp 5 - 7
Anion/Non metal
Gp 5 Gp 6 Gp 7
Oxidation
state
Oxidation
state
Oxidation
state
- 3 - 2 - 1
N 3-
O 2-
F1-
P 3-
S2-
CI 1-
Cation/Metal
Gp 1 Gp 2 Gp 3
Oxidation
state
Oxidation
state
Oxidation
state
+1 +2 +3
Na1+
Mg2+
Al 3+
K1+
Ca 2+
Ga 3+
4
CI2
0 0 0 0 0
+1 +2 -2 -1 -2
CI- S2-
ON for transition metal varies
Transition metal ions
Transition metals ions
(variable oxidation states)
Sc
+3
Ti
+2
+3
V
+2
+3
Cr
+2
+3
+6
Mn
+2
+3
+6
+7
Fe
+2
+3
Co
+2
+3
Ni
+2
Cu
+1
+2
Zn
+2
Sc 3+
Ti 2+
Ti3+
V 2+
V 3+
Cr 2+
Cr 3+
Cr 6+
Mn 2+
Mn 3+
Mn 6+
Mn 7+
Fe 2+
Fe 3+
Co 2+
Co 3+
Ni 2+
Cu 1+
Cu 2+
Zn 2+
Oxidation
number
Diff ON
Charge on ion
Click here on oxidation rulesClick here view simple step
Notes
Sc3+
Charge on Sc
Oxidation
number
+3
Oxidation
state
-+
3+

10. ON all atoms in polyatomic ion add up to
charge of polyatomic ion
ON all atoms in neutral molecule add up to 0
CO3
2-
SO4
2-
H2SO4 CO2
5
Oxidation Number/ON Rules
HNO3
(+1)2 + (+6) + (-2)4 = 0
+1 +6 -2
(+4) + (-2)2 = 0 (+1) + (+5) + (-2)3 = 0
+4 -2 +1 +5 -2
(+4) + (-2)3 = -2
+4 -2
(+6) + (-2)4 = -2
NO3
1-
+6 -2
(+5) + (-2)3 = -1
+5 -2
7 ON atom/molecule of element = 0
(NOT combined)
H2 CI2 O2 Fe Cu Mg
0 0 0 0 0 0
8 Monoatomic ion – ON same as charged on ion
Ionic
compound
Charge ion Oxidation number
MgF2 Mg 2+
F 1-
Mg (+2) F (-1)
NaCI Na 1+
CI 1-
Na (+1) CI (-1)
KBr K1+
Br 1-
K (+1) Br (-1)
CaI2 Ca 2+
I 1-
Ca (+2) I (-1)
Li3N Li 1+
N 3-
Li (+1) N (-3)
Al2O3 Al 3+
O 2-
AI (+3) O (-2)
9
Formula
compound
Charge Oxidation
number
Name using oxidation
number
FeO Fe 2+
or 2+ +2 Iron (II) oxide
Fe2O3 Fe 3+
or 3+ +3 Iron (III) oxide
Cu2O Cu 1+
or 1+ +1 Copper (I) oxide
CuO Cu 2+
or 2+ +2 Copper (II) oxide
MnO2 Mn 4+
or 4+ +4 Manganese (IV) oxide
MnO4
-
Mn 7+
or 7+ +7 Manganese (VII) oxide
K2Cr2O7 Cr 6+
or 6+ +6 Potassium dichromate
(VI)
Cr2O3 Cr 3+
or 3+ +3 Chromium (III) oxide
Click here view chemguide notes
6

11. Oxidation Number/ON Rules
9 Metal more than one oxidation states, Roman numeral used
Manganese Chromium
Ionic
compound
MnSO4 MnO2 K2MnO4 KMnO4 K2Cr2O7 Cr2O3
Oxidation
Number
(+2) + (+6) + (-2)4 = 0
Mn (+2)
(+4) + (-2)2 = 0
Mn (+4)
(+1)2 + (+6) + (-2)4 = 0
Mn (+6)
(+1) + (+7) + (-2)4 = 0
Mn (+7)
(+1)2 + (+6)2 + (-2)7 = 0
Cr (VI)
(+3)2 + (-2)3 = 0
Cr (III)
IUPAC
name
Manganese
(II)
sulphate
Manganese
(IV)
oxide
Manganese
(VI)
Manganese
(VII)
Chromium
(VI)
Chromium
(III)
Iron Copper
Ionic
compound
FeCI2 FeCI3 CuCI CuCI2
Oxidation
Number
(+2) + (-1)2 = 0
Fe (+2)
(+3) + (-1)3 = 0
Fe (+3)
(+1) + (-1) = 0
Cu (+1)
(+2) + (-1)2 = 0
Cu (+2)
IUPAC
name
Iron (II) chloride Iron (III) chloride Copper (I) chloride Copper (II) chloride
Vanadium
VO2
+
VO 2+
(+5) + (-2)2 = +1
V (+5)
(+4) + (-2) = +2
V (+4)
Vanadium (V) Vanadium (IV)
ON for underlined element in ionic compound10
Na2SO3 Na2SO4 NaNO2 NaNO3 (SO3)2-
(SO4)2-
(+1)2 + (+4) + (-2)3 = 0 (+1)2 + (+6) + (-2)4 = 0 (+1)+ (+3) + (-2)2 = 0 (+1)+ (+5) + (-2)3 = 0 (+4) + (-2)3 = -2 (+6) + (-2)4 = -2
ON for S = +4 ON for S = +6 ON for N = +3 ON for N = +5 ON for S = +4 ON for S = +6
+1 +4 -2 +1 +6 -2 +1 +3 -2 +1 +5 -2 +4 -2 +6 -2

12. Oxidation Number/ON Rules
11 ON for underlined element in compound
OH-1
PO4
3-
S2O3
2-
CN-1
OCI-1
H2O2 (HCO3)-1
(-2) + (+1) = -1 (+5) + (-2)4 = -3 (+2)2 + (-2)3 = -2 (+4) + (-5) = -1 (-2) + (+1) = -1 (+1)2 + (-1)2 = 0
ON for O = -2 ON for P = +5 ON for S = +2 ON for C = +4 ON for O = -2 ON for O = -1 ON for C = +4
(+1) + (+4) + (-2)3 = -1
-2 +1 +5 -2 +2 -2 +4 -5 -2 +1 +1 -1 +1 +4 -2
Oxidation Reduction
Gain oxygen ↑ Loss oxygen ↓
Loss hydrogen ↓ Gain hydrogen ↑
Redox (Oxidation and Reduction)
Rxn involve gain/loss of oxygen/hydrogen
CH4 + 2O2 → CO2 + 2H2O
Gain hydrogen
Oxygen reduction
gain oxygen
Carbon oxidation
Rxn involve gain/loss of electron
Oxidation Reduction
Gain ON ↑ Loss ON ↓
Loss electron ↓ Gain electron ↑
- broader definition
- cover more rxn types
PbO + CO Pb + CO→ 2
Lead Reduction
gain oxygen
Carbon oxidation
(-4) (+4)
(0) (-2)
ON ↑
ON ↓
oxygen reduced
carbon oxidized
PbO + CO Pb + CO→ 2
(+2) (0)
lead reduced
(+2) (+4)
CH4 + 2O2 → CO2 + 2H2O
ON ↑
carbon oxidized
ON ↓
loss oxygen

13. Redox (Oxidation and Reduction)
• Assuming bond are ionic with diff EN values (unless bet same element)
• Assign each atom, measure of electron control relative to atom in pure element
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
Oxidation Number/ON Rules
H CI
xx
xx
•
x
∂-∂+
+1 -1Oxidation number
Oxidation state (sign, number) +2 NOT 2+
Oxidation state useful tool for electron book- keeping. They are not REAL!
- Oxidation state -Assume bond ionic with diff EN values (unless bet same element)
xx
Na CI
Oxidation Number/ON Rules Imagine electron move to more EN element
xx
xx
xx
o
x
+1 -1
Complete transfer
Na CI
+1 -1
Ionic compound
H CI
Covalent compound
xx
xx
+1 -1
xx
o
x
H CI
Unequal sharing
+1 -1
Organic Covalent compound
H C O H
H
H
o
x
o
x
o
X
o
X
o
x
oo
-2
+1
+1
+1
+1 -2
C H4 O
Unequal sharing
Still covalent bond
Treat as imaginary ionic (loss/gain of electron control)
Bonds are still covalent NOT ionic, keep track where electron going
-2 +1 -2
(+1) + (-1) = 0 (+1) + (-1) = 0
(-2) + (+1)4 + (-2) = 0
O S O
O
oo
xx
oo
xx
oo
xx
-2 +6 -2
-2
S O3
+6 -2
(+6) + (-2)3 = 0Click here note ON for organic carbon
oo oo
oo
o
o
o
o
o
o

14. ON for carbon
is NOT -2
Oxidation Number/ON Rules
• Assuming bond are ionic with diff EN values (unless bet same element)
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
- Oxidation state useful tool for electron book- keeping. They are not REAL!
Oxidation state (sign, number) +2 NOT 2+
Click here here note ON carbon
H C C H
Oxidation state Carbon compound
-4 CH4
-3 C2H6
-2 CH3CI
-1 C2H2
0 CH2CI2
+1 CHCI2-CHCI2
+2 CHCI3
+3 C2CI6
+4 CCI4
ON carbon (Organic molecules)
Average oxidation number bet carbon is taken!
Different ON states
Don’t need to take average ON bet carbons
Oxidation
state
Carbon
compound
-3 and -1 CH3CH2OH
-3 and +1 CH3CHO
Different ON states
o
x
o
x
+1 -1 -1 +1
C2 H2
-1 +1
ox
ox
ox
Equal sharing
(-1)2 + (+1)2 = 0
H C C O H
H
H
o
X
o
x
o
X
o
X
oo
o
x
o
x
H
H
o
X
oo
o
x
+1
+1
-2
+1
+1
+1
+1-1-3
C2 H6 O1
x +1 -2
2x + 6 -2 = 0
x = -2
ON C in CH3 = -3
ON C in CH2 = -1
Average ON C = -2
H C C O
H
o
x
+1
H
H
o
X
o
X
o
x
o
X
oo
xo
xo
oo
+1
+1 +1
-3
-2
+1
C2 H4 O1
x +1 -2
2x + 4 -2 = 0
x = -1
ON for carbon
is NOT -1
ON C in CH3 = -3
ON C in CH = +1
Average ON C = -1

15. ON C in CH3 = -3
ON C in COOH = +1
Average ON C = 0
+3
Oxidation Number/ON Rules
• Assuming bond are ionic with different EN values (unless bet same element)
• Apparent/imaginary charge it has when bonded to diff elements
• Unequal sharing electron based on electronegativity
- Oxidation state useful tool for electron book- keeping. They are not REAL!
Oxidation state (sign, number) +2 NOT 2+
Click here here note ON carbon
ON carbon (Organic molecules)
Average oxidation number bet carbon is taken!
Oxidation
state carbon
Carbon
compound
-3 and +3 CH3COOH
H C C O H
H
H
o
X
o
x
o
X
o
X
oo
o
x
o
x
H
H
o
X
oo
o
x
+1
+1
-2
+1
+1
+1
+1-1
C2 H6 O1
x +1 -2
2x + 6 -2 = 0
x = -2
ON C in CH3 = -3
ON C in CH2 = -1
Average ON C = -2
H C C O
H
o
x
+1
H
H
o
X
o
X
o
x
o
X
oo
xo
xo
oo
+1
+1 +1
-3
-2
+1
C2 H4 O1
x +1 -2
2x + 4 -2 = 0
x = -1
ON for carbon
is NOT -2
ON for carbon
is NOT -1
ON C in CH3 = -3
ON C in CH = +1
Average ON C = -1
H C C O H
H O
H
+1
o
x
o
X
+1
+1
o
X
-3 -3
o
x
+1
oo
oo
oo
oo
xx
o
o
o
x
o
x
-2
ON for carbon
is NOT 0
C2 H4 O2
x +1 -2
2x + 4 -4 = 0
x = 0
Oxidation
state carbon
Carbon
compound
-3 and -1 CH3CH2OH
Oxidation
state carbon
Carbon
compound
-3 and +1 CH3CHO

16. NOT Redox rxn
•NO Loss/gain electron
•NO change in oxidation number
Concept Map
Type of chemical reaction
Combustion/Respiration rxn Displacement rxn
Synthesis rxn Decomposition rxn
Single
Displacement
Double
Displacement
Acid/Base rxn
Involve oxygen!!
CH4 + 2O2 CO→ 2+ 2H2O C6H12O6 +6O2 6CO→ 2+6H2O
Redox rxn
•Loss/gain electron
•Change in oxidation number
Zn + 2HCI H→ 2+ ZnCI2 Zn + CuO ZnO + Cu→
Redox rxn
•Loss/gain electron
•Change in oxidation number
KI + Pb(NO3)2 PbI→ 2 + KNO3
Type of chemical reaction
HCI + NaOH NaCI + H→ 2O MgO + 2HCI MgCI→ 2 + H2O 2H2 + O2 2H→ 2O 2KCIO3 2KCI + 3O→ 2
Redox rxn
•Loss/gain electron
•Change in oxidation number
Redox rxn
•Loss/gain electron
•Change in oxidation number
NOT Redox rxn
•NO Loss/gain electron
•NO change in oxidation number
H CI + Na O H NaCI + H→ 2 O
+1 -1 +1 -2 +1 +1 -1 +1 -2
2H2 + O2 2H→ 2O
0 0 +1 -2
2K CI O3 2K CI + 3O→ 2
+1 +5 -2 +1 -1 0
C6 H12 O6 + 6O2 6C O→ 2 + 6H2 O Zn + 2H CI H→ 2 + Zn CI2
0 +1 -1 0 +2 -1
K I + Pb (N O3)2 Pb I→ 2 + K N O3
+1 -1 +2 +5 -2 +2 -1 +1 +5 -20 +1 -2 0 +4 -2 +1 -2

17. Oxidation
state
Carbon
compound
-4 CH4
-3 C2H6
-2 CH3CI
-1 C2H2
0 CH2CI2
+1 CHCI2-CHCI2
+2 CHCI3
+3 C2CI6
+4 CCI4
Different ON/ states for Carbon Different ON/ states for sulphur
Carbon attach to H
– ON lower ↓
- Carbon less oxidized
- Carbon attract electron
Carbon attach to CI/O (EN ↑)
– ON higher ↑
- Carbon more oxidized
- Carbon lose electron
Oxidation
state
Sulphur
compound
-2 H4S
0 S8
+2 SCI3
+4 SO2
+4 SO3
2-
+6 SO3
+6 H2SO4
Sulphur attach to H /CI
– ON lower ↓
- Sulphur less oxidized
- Sulphur attract electron
Sulphur attach to O (EN ↑)
– ON higher ↑
- Sulphur more oxidized
- Sulphur lose electron
Oxidation numbers and name
Formula
ion
Charge Oxidation
number
Name using ON
CrO4
2-
2- ON for Cr +6 Chromate (VI)
Cr2O7
2-
2- ON for Cr +6 Dichromate (VI)
MnO4
-
1- ON for Mn +7 Manganate (VII)
MnO4
2-
2- ON for Mn +6 Manganate (VI)
CIO-
1- ON for CI +1 Chlorate (I)
CIO3
-
1- ON for CI +5 Chlorate (V)
CIO2
-
1- ON for CI +3 Chlorate (III)
CIO4
-
1- ON for CI +7 Chlorate (VII)
Formula
compound
Charge Oxidation
number
Name using oxidation
number
FeO Fe 2+
or 2+ +2 Iron (II) oxide
Fe2O3 Fe 3+
or 3+ +3 Iron (III) oxide
Cu2O Cu 1+
or 1+ +1 Copper (I) oxide
CuO Cu 2+
or 2+ +2 Copper (II) oxide
MnO2 Mn 4+
or 4+ +4 Manganese (IV) oxide
MnO4
-
Mn 7+
or 7+ +7 Manganese (VII) oxide
K2Cr2O7 Cr 6+
or 6+ +6 Potassium dichromate
(VI)
Cr2O3 Cr 3+
or 3+ +3 Chromium (III) oxide

18. Period 2
Shared electron cloud closer to O
Electronegativity
Electronegativity (EN)
•Tendency of atom to attract/pull shared/bonding electron to itself
•EN value higher – pull/attract electron higher (EN value from 0.7 – 4)
EN highestEN lowest
Factors affecting EN value
•Size of atom/distance – small size/distance – stronger attraction for electron
•Nuclear charge – higher nuclear charge – stronger attraction for electron
Electronegativity
•EN increase up a Group
•EN increase across a Period
F
CI
Br
I
Size increase 
Attraction electron decrease 
EN lower 
Size
Be
+4
Li
+3
B
+5 N
+7
O
+8 F
+9
EN increase  across period 2
Nuclear charge
EN increase  across period 2
Nuclear charge increase 
Strong attraction for electron 
EN increase 
Gp 17
C
+6
EN decrease  down gp 17

19. FORMAL CHARGE (FC)
Tool/Model for comparing which Lewis structures is more acceptable
Lewis structure SO2
Which is
acceptable?
Lewis structure SO3
Formal Charge
•Treats covalent bond with equal electron distribution no EN diff bet atom
•Electronegative atom has negative while least electronegative atom has positive formal charge.
Formula formal charge
Click here video formal chargesClick here video formal charges
V - valence electrons of atom
L – Lone pair electron
B - electrons shared in covalent bonds in the molecule
✓ ✓
All resonance structure contribute to electronic structure.
Real structure is combination of them.
Lowest formal charge (stable), contribute more than less stable structure.
Sum of formal charges must be zero for neutral or equal to charge on ion.
L +
Formal charge
concept
Formal charge NOT real !!

20. Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenses
http://creativecommons.org/licenses/
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorial
http://lawrencekok.blogspot.com