An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron. Redox reactions are common and vital to some of the basic functions of life, including photosynthesis, respiration, combustion, and corrosion or rusting.

Oxidation and Reduction Reactions

Introduction:
Oxidation and reduction are two fundamental chemical processes that are commonly referred to as redox reactions. These reactions involve the transfer of electrons between reactant species. Oxidation refers to the loss of electrons by a substance, while reduction refers to the gain of electrons by a substance.

Definition:
- Oxidation: It is a process in which a substance loses electrons, resulting in an increase in its oxidation state.
- Reduction: It is a process in which a substance gains electrons, leading to a decrease in its oxidation state.

Key Concepts:
- Oxidation state: It is a measure of the degree of oxidation or reduction of an atom within a compound.
- Oxidizing agent: It is a species that causes the oxidation of another substance by accepting electrons.
- Reducing agent: It is a species that causes the reduction of another substance by donating electrons.

The Process:
1. Identify the reactants: Determine the substances involved in the redox reaction and their initial oxidation states.
2. Assign oxidation states: Assign oxidation states to each atom in the reactants. Oxidation states can be determined based on a set of rules.
3. Identify the oxidized and reduced species: Identify the species that undergo oxidation and reduction by comparing their initial and final oxidation states.
4. Write half-reactions: Separate the oxidation and reduction processes into individual half-reactions. In the oxidation half-reaction, the species that is oxidized is written on the left side of the equation, while in the reduction half-reaction, the species that is reduced is written on the left side of the equation.
5. Balance the atoms: Balance the number of atoms on both sides of each half-reaction by adding coefficients as needed.
6. Balance the charges: Balance the charges on both sides of each half-reaction by adding electrons as needed. The number of electrons gained in the reduction half-reaction should equal the number of electrons lost in the oxidation half-reaction.
7. Combine the half-reactions: Multiply each half-reaction by the appropriate factor so that the number of electrons gained in the reduction half-reaction equals the number of electrons lost in the oxidation half-reaction. Add the two half-reactions together to obtain the balanced overall redox reaction.
8. Check the balanced equation: Verify that the number of atoms and the charge are balanced on both sides of the overall redox reaction.

Conclusion:
The process of oxidation and reduction reactions involves the transfer of electrons between reactant species. By following the steps of identifying reactants, assigning oxidation states, and balancing half-reactions, a balanced overall redox reaction can be obtained. These reactions play a crucial role in various chemical and biological processes.