1. Displacement reactions
recombine ions
Acid-Base reactions
H+ transfer
Fe2O3 (s)
+ Al (s) 
Al2O3 (s)
+ Fe
(l)
thermite reaction
Oxidation-Reduction reactions
(redox)
e- transfer
Fe2O3 =
iron ( )
III
oxide
Fe3+
Fe (l) =
Fe0
Fe3+ has_____ protons 26
Fe0 has _____ protons 26
Fe3+ has ____ electrons 23
Fe0 has ____ electrons 26
Fe3+ gained 3 electrons
gaining e- =
reduction
reducing the oxidation state 3+ 

2. Fe2O3 (s)
+ Al (s) 
Al2O3 (s)
+ Fe
(l)
Al (s) =
Al0
Al2O3
aluminum oxide
Al0 has _____ electrons 13
Al3+has ______ electrons 10
oxidation state =
oxidation state = 3+
Al0 loses___ e- 3
losing e-
= oxidation
increase oxidation number  3+
LEO
GER
Lose
Electrons
Oxidation
Gain
Electrons
Reduction

3. Rules for oxidation numbers
1. Oxidation number for elements is zero.
N2,
O2,
Na(s),
Co(s),
He (g)
Oxidation number of monatomic ions
is the same as their charge
Group IA = +1
Al3+, Zn2+, Cd2+, Ag+
Group IIA = +2
Oxidation number of oxygen in most compounds
is –2. Exceptions:
H2O2,
O2-
(peroxides) –1
4. Oxidation number of hydrogen is +1
Exceptions:
bonded to metals LiH
5. Fluorine is always –1.
Other halogens are –1.
Exceptions:
bonded to O, they are positive

4. Assign oxidation numbers to all of the elements:
Li2O
Li = +1
O = -2
PF3
P = +3
F = -1
HNO3
H = +1
N = +5
O = -2
MnO4-
Mn = +7
O = -2
Cr2O72-
Cr = +6
O = -2

5. What is the oxidation state of the highlighted element?
P2O5 +5
diphosphorous pentoxide
NaH -1
sodium hydride
SnBr4 +4
tin (IV) bromide
BaO2 -1
barium peroxide

6. Redox reactions +1 +2
Zn (s)
+ 2H+ (aq) 
H2 (g)
+ Zn 2+ Zn  +2
increase
oxidation state
lose
electrons
oxidized
reducing agent H +1 
decrease
oxidation state
gain
electrons
reduced
oxidizing agent

7. +1 -2
2H2(g)
+ O2 (g) 
2H2O(l) H
loses or gains electrons
is oxidized or reduced
oxidizing or reducing agent O
loses or gains electrons
is oxidized or reduced
oxidizing or reducing agent

8. +7 +3 +4
2H2O
+ Al(s)
+ MnO4- 
Al(OH)4-
+ MnO2
H2O
What is being oxidized? Al
What is oxidation?
MnO4-
LEO
Al(OH)4-
MnO2
How many e-?
What is being reduced?
GER
What is the reducing agent?

9. What is the oxidation state of S in each of these
compounds:
H2S
S = -2
H = +1 S8
S =
SCl2
S = +2
Cl = -1
Na2SO3
S = +4
O = -2
Na = +1
SO42-
S = +6
O = -2
Which of these compounds can not act as a
reducing agent?
Which of these compounds can not act as a
oxidizing agent?

10. +4 -2 +1 -2 +2 -2 +1 +2 -2 +1
Cd(s)
+ NiO2
+ 2H2O 
Cd(OH)2
+ Ni(OH)2
What is being oxidized?
What is being reduced?
What is the oxidizing agent?
What is the reducing agent?
How many electrons are transferred?