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Oxidation and Reduction

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  • Oxidation-reduction or redox reactions involve the transfer of electrons between one reactant and another in such a way that the oxidation state of the reactants changes.

    IUPAC has defined oxidation as follows:[1]

    1. The complete, net removal of one or more electrons from a molecular entity (also called ‘de-electronation’).
    2. An increase in the oxidation number of any atom within any substrate.
    3. Gain of oxygen and/or loss of hydrogen of an organic substrate.

    Reduction is defined as the reverse:[2]

    "The complete transfer of one or more electrons to a molecular entity (also called ‘electronation’), and, more generally, the reverse of the processes described under oxidation (2) and (3)."

    An oxidant or oxidising agent is a substance which causes another substance to be oxidised, and the oxidant will itself be reduced in the redox reaction.

    Wikipedia describes redox reactions as follows:

    "Redox (portmanteau for reduction-oxidation) reactions describe all chemical reactions in which atoms have their oxidation state changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of glucose (C6H12O6) in the human body through a series of complex electron transfer processes.
    Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid-base reactions. Fundamentally, redox reactions are a family of reactions that are concerned with the transfer of electrons between species.
    The term comes from the two concepts of reduction and oxidation. It can be explained in simple terms:
    • Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
    • Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion."

    Redox experiments

    Note that links in red represent pages that still need to be created.

    Intermediate level

    Suitable for UK GCSE level and US high schools. Corrosion and rusting

    The experiments in this section illustrate oxidation and reduction processes such as corrosion and rusting.

    Based on the Experimentation hub collection: [1]

    Quizzes covering redox chemistry

    Intermediate level

    Suitable for UK GCSE level.


    Chemical Mahjong from Stetson University - default game is on oxidation numbers.


    • Martin A. Walker (Dept. of Chemistry State University of New York at Potsdam)