04_Oxidation Numbers_Worksheet1 - Name:_ Page | 1...

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REDOX REACTIONS & OXIDATION NUMBERS
INTRODUCTION
Oxidation-Reduction (redox) reactions take place in the world at every moment. The
way batteries produce electricity, the process by which iron rusts, photosynthesis,
bleaching your hair—all of these are examples of redox reactions. Redox reactions
refer to the pair of reactions: Reduction (the gain of electrons by one reactant) and
Oxidation (the loss of electrons by the other reactant.) These processes always occur
together—if one substance is being reduced, that means the other species is being
oxidized. And since the electrons lost by one species are being gained by the other
species, there is no net gain/loss of electrons overall.
As the term “oxidation” might suggest, many redox reactions involve the reaction of a
substance with oxygen, for example, the rusting of iron:
4 Fe (s) + 3 O
2
(g)  2 Fe
2
O
3
(s)
In this reaction, iron is being oxidized, while oxygen is being reduced. However, IT IS
IMPORTANT TO REMEMBER that many redox reactions do not involve oxygen at all,
for example, the formation of sodium chloride:
2 Na (s) + Cl
2
(g)  2 NaCl(s)
This gives rise to the fundamental definition of Oxidation: Loss of Electrons , and
conversely fundamental definition of Reduction: Gain of Electrons.