Balancing Redox Equations

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Oxidation-Reduction Reaction Noun

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[ok-si-day-shun ri-duk-shun ree-ak-shun]

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Oxidation-Reduction Reaction

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A chemical reaction involving the complete or partial transfer of electrons from one substance to another, also known as a redox reaction.

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Example: This image shows a balanced chemical reaction where atoms in the reactants (left) are rearranged to form the products (right), with no atoms lost.

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Oxidation Noun

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[ok-si-day-shun]

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Oxidation

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The chemical process where an atom or ion loses one or more electrons, causing an increase in its oxidation number.

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Example: This diagram shows that oxidation is the process where an atom (A) loses an electron, causing its charge to become more positive.

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Reduction Noun

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[ri-duk-shun]

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Reduction

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The chemical process where an atom or ion gains one or more electrons, causing a decrease in its oxidation number.

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Example: This diagram shows atom B gaining an electron from atom A. This gain of a negatively charged electron is called reduction.

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Oxidation Number Noun

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[ok-si-day-shun num-ber]

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Oxidation Number

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A number assigned to an element in a compound that represents its degree of oxidation or the electrons lost or gained.

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Example: In a water molecule, each hydrogen atom has an oxidation number of +1, and the oxygen atom has an oxidation number of -2.

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Oxidizing Agent Noun

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[ok-si-dy-zing ay-jent]

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Oxidizing Agent

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A substance in a redox reaction that accepts electrons from another species, thereby causing oxidation and becoming reduced itself.

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Example: In this reaction, iron oxide (Fe₂O₃) gives its oxygen to carbon monoxide (CO). Because it causes oxidation and is itself reduced, Fe₂O₃ is the oxidizing agent.

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Reducing Agent Noun

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[ri-doo-sing ay-jent]

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Reducing Agent

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A substance in a redox reaction that donates electrons to another species, thereby causing reduction and becoming oxidized itself.

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Example: This diagram shows that a reducing agent (A) is a substance that loses electrons and becomes oxidized in a chemical reaction.

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Species Noun

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[spee-sheez]

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Species

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In chemistry, any kind of chemical unit involved in a process, which can be an atom, molecule, or ion.

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Example: This key defines different chemical species, which are the atoms, ions, or molecules like Na+ or H2O that participate in a chemical reaction.

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Half-Reaction Noun

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[haf ree-ak-shun]

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Half-Reaction

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An equation showing either the oxidation or the reduction part of a redox reaction, including the electrons lost or gained.

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Example: This diagram shows a chemical reaction split into two parts. Each part is a 'half-cell' where one 'half-reaction' happens: the oxidation half-cell and the reduction half-cell.

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Oxidation Half-Reaction Noun

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[ok-si-day-shun haf ree-ak-shun]

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Oxidation Half-Reaction

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The part of a redox reaction equation that shows the species being oxidized and the corresponding electrons that are lost.

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Example: The top equation shows an iron ion (Fe²⁺) changing into a different iron ion (Fe³⁺), which is the oxidation half of a larger reaction.

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Reduction Half-Reaction Noun

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[ri-duk-shun haf ree-ak-shun]

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Reduction Half-Reaction

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The part of a redox reaction equation that shows the species being reduced and the corresponding electrons that are gained.

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Example: In the beaker on the left, copper ions (Cu²⁺) gain two electrons (2e⁻) to become solid copper (Cu), which is a reduction half-reaction.