What is a redox reaction?

• Oxidation is when an element combines with oxygen to give an oxide. For example, the oxide of hydrogen is water. Oxidation can be defined as the gain of oxygen, the loss of hydrogen, or the loss (or partial loss) of electrons.
• Reduction, the opposite chemical reaction of oxidation, occurs when oxygen is removed from a compound.

Because oxidation and reduction reactions occur simultaneously they are commonly referred to as redox-reactions.

Why is oxygen so reactive?

When oxygen reacts with any other element (except fluorine), electrons are pulled towards the oxygen and away from the other element in the bond. This attraction of the shared electrons by the oxygen results in the formation of a negative ion, which will react with any positively charged molecule.

Distribution of charges in a molecule of water. The slightly negative field around the oxygen results from its ability to pull electrons away from other elements—in this case, hydrogen. The hydrogens then have a slightly positive field.

Learn more about chemical bonding.