Concept of Oxidation and reduction

The formal name for a redox reaction is "oxidation reduction reaction," and you can see that "redox" is just shorthand for the words reduction and oxidation. Thus, in a redox reaction, two things happen. You guessed it -- oxidation and reduction. These two have to happen together. You cannot have an oxidation reaction without a corresponding reduction reaction. It’s a bit like the idea behind a blood transfusion or an organ transplant. You cannot have a recipient unless you have a donor, and it does not make any sense to be a donor unless there is a recipient. You may have noticed that "oxidation" starts with the same prefix as oxygen, suggesting that oxygen may be somehow involved in this process.

Oxidation is the gaining of bonds to oxygen

Organic fuel substances (such as wood, coal or gas) are examples of compounds that can be oxidized. In the process of burning, the carbon in these substances becomes bonded with oxygen, while some of the oxygen used to "burn" the fuel bonds to the hydrogen atoms from the fuel.

Reduction is the gaining of hydrogen

Therefore, combustion reactions are good examples of redox reactions where one molecule gains oxygen (is oxidized) and one molecule gains hydrogen (is reduced). For example, let’s look at what happens when gasoline in your car is burned as you drive around town.

C7H12 + 11O2 = 7O2 + 8H2O

Note how the carbon atoms in heptane are oxidized (because the carbon atoms in heptane become bonded with oxygen atoms), while the oxygen is reduced (becomes bonded with hydrogen atoms).

These definitions of oxidation and reduction are useful. However, more general definitions of oxidation and reduction involve the movement of electrons between the compounds involved in the redox reaction.