View source for Redox

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	Reduction<br />
	Oxidant + e<sup>&ndash;</sup> &xrarr; Product<br />
	(Electrons '''gained'''; oxidation number '''decreases''')<br />
	<br />
	Oxidation<br />
	Reductant &xrarr; Product + e<sup>&ndash;</sup><br />
	(Electrons '''lost'''; oxidation number '''increases''')
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|caption = The two parts of a redox reaction
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[[Image:Rust03102006.JPG|thumb|250px|Rusting iron]]
[[Image:Large bonfire.jpg|thumb|250px|A bonfire. Combustion consists of redox reactions involving [[Radical (chemistry)|free radicals]].]]
{{TopicTOC-Chemistry}}

'''Redox''' (shorthand for '''reduction/oxidation''') describes all [[chemical reaction]]s in which atoms have an increase or decrease in [[oxidation number]] ([[oxidation state]]).<ref>This can be a simple redox process, such as the [[oxidation]] of [[carbon]] to yield [[carbon dioxide]], the reduction of carbon by [[hydrogen]] to yield [[methane]] (CH<sub>4</sub>), or a complex process such as the oxidation of sugar in the human body, through a series of very complex [[electron transfer]] processes.</ref>

An oxidation number is a number assigned to an [[element]] in chemical combination that represents the number of electrons lost (or gained, if the number is negative), by an atom of that element in the compound.

The term ''redox'' comes from the two concepts of '''red'''uction and '''ox'''idation. It can be explained in simple terms:
*'''''Oxidation''''' describes the '''''loss''''' of [[electron]]s by a [[molecule]], [[atom]] or [[ion]]
*'''''Reduction''''' describes the '''''gain''''' of electrons by a molecule, atom or ion

Whether an electron is gained or lost can be easily memorised by the abbreviation OIL RIG, which stands for, "Oxidation Is Loss," or losing electrons, and "Reduction Is Gain," or gaining electrons. Redox reactions can also happen by sharing electrons to form a product by [[covalent bond|covalent bonding]].  

In an oxidation reduction reaction, the cation gives an electron to the anion because both ions will have a different charge to attract each other with. In an oxidation reduction reaction, the oxidizing [[reagent]] pulls an electron from the other atom to have a net positive charge. The reducing reagent gives an electron to have a net negative charge. However, there are exceptions.<ref>Oxidation and reduction properly refer to ''a change in oxidation number'' – the actual transfer of electrons may never occur. Thus, oxidation is better defined as an ''increase in oxidation number'', and reduction as a ''decrease in oxidation number''. In practice, the transfer of [[electrons]] will always cause a change in oxidation number, but there are many reactions which are classed as "redox" even though no electron transfer occurs (such as those involving [[covalent]] bonds).</ref> 

== Chemical process ==
Redox is a chemical process. It can be described in [[chemical formula]]<nowiki/>s. This example describes the process that occurs in a [[blast furnace]], where [[iron]] (Fe) reacts with carbon (C):
:<math>\mathrm{1) \ C + O_2 \longrightarrow CO_2}</math>

:<math>\mathrm{2) \ CO_2 + C \rightleftharpoons 2 \ CO}</math>

:<math>\mathrm{3) \ Fe_2O_3 + 3 \ CO \longrightarrow 3 \ CO_2 + 2 \ Fe}</math>
:<small>Now elementary iron has been processed.</small>

==Related pages==
* [[Electrochemistry]]

== Notes ==
{{reflist}}

== Other websites ==
{{wikibooks|General Chemistry/Redox Reactions}}
* [http://www.shodor.org/UNChem/advanced/redox/redoxcalc.html Redox reactions calculator]
* [http://www.chemguide.co.uk/inorganic/redox/definitions.html#top Redox reactions at Chemguide]
* [http://www.webqc.org/balance.php Online redox reaction equation balancer, balances equations of any half-cell and full reactions]

{{Basic reaction mechanisms}}


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[[Category:Chemical reactions]]