Redox Reaction
Ag+(aq) + e- → Ag (s)
According to modern theory, the gain of electrons is called reduction.
Cu(s) → Cu2+(aq) + 2e-
According to modern theory, the loss of electrons is called oxidation.
Theory suggests that the total number of electrons gained in a reaction must equal the total number of electrons lost. Also, oxidation and reduction are separate processes. This theoretical description requires oxidation and reduction to occur simultaneously rather than sequentially. Oxidation–reduction reactions are often simply called “redox” reactions.
Electron Transfer Theory
A redox reaction is a chemical reaction in which electrons are transferred between particles.
• The total number of electrons gained in the reduction equals the total number of electrons lost in the oxidation.
• Reduction is a process in which electrons are gained.
• Oxidation is a process in which electrons are lost.
Oxidation State
In order to describe oxidation and reduction of molecules and polyatomic ions, chemists have developed a method of “electron bookkeeping” to keep track of the loss and gain of electrons. The method is arbitrary but it works well. In this system, the oxidation state of an atom in an entity is defined as the apparent net electric charge that an atom would have if electron pairs in covalent bonds belonged entirely to the more electronegative atom.
Oxidation number a positive or negative number corresponding to the apparent charge that an atom in a molecule or ion would have if the electron pairs in covalent bonds belonged entirely to the more electronegative atom