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Oxidation and Reduction
reduction, often associated with producing metals from compounds
oxidation, often associated with reactions with oxygen, combustion and corrosion
Electron Transfer Theory

every redox reaction is made up of two simultaneous half reactions

electrons are gained in one of the half reactions (reduction) and lost in the other half reaction (oxidation)
Example:
a piece of copper placed into silver nitrate solution
Cu
+
AgNO3
Cu(NO3)2
Cu0
Half Reactions:
Cu2+
Ag+
2e1Ag
LEO says GER
the nitrate ion is a spectator ion
number of electrons gained must equal electrons lost
Cu0(s)
2Ag+(aq)
+ 2e+
2 Ag (aq) + Cu
Therefore:



Ag
+
e1-
+
Copper loses two electrons- oxidation
Silver gains one electron- reduction


+
Cu2+(aq) +
2e2 Ag(s)
Cu2+ + 2 Ag
(x2)
net ionic equation: add both half reactions
Oxidizing agent: causes a substance to be oxidized
Reducing agent: causes a substance to be reduced
Oxidation States

more complicated compounds need better electron tracking

oxidation state: apparent net charge that the more electronegative atom would have if it owned shared
electrons completely
Oxidation Numbers
Atom or Ion
all atoms in elements
Hydrogen in most compounds
Hydrogen in hydrides
oxygen in all compounds
Oxygen peroxides
all monatomic ions
Oxidation number
charge on ion
Example:
Find the oxidation number for nitrogen in sodium nitrate NaNO3
total charge must on all compounds is = 0
+1
Na
x
N
0 = +1
+
x
-2
O
-6
x=5
The oxidation number for nitrogen in NaNO3 is +5.
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Some oxidation numbers change in a redox reaction
-2
O
-2
O