Everything about Oxidised totally explained
Redox (shorthand for
reduction/oxidation reaction) describes all
chemical reactions in which atoms have their
oxidation number (
oxidation state) changed.
This can be either a simple redox process such as the oxidation of
carbon to yield
carbon dioxide, or the reduction of
carbon by
hydrogen to yield
methane (CH
4), or it can be a complex process such as the oxidation of
sugar in the human body through a series of very complex
electron transfer processes.
The term
redox comes from the two concepts of
reduction and
oxidation. It can be explained in simple terms:
Though sufficient for many purposes, these descriptions are not precisely correct. 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).
Non-redox reactions, which don't involve changes in
formal charge, are known as
metathesis reactions.
Oxidizing and reducing agents
Substances that have the ability to
oxidize other substances are said to be
oxidative and are known as
oxidizing agents,
oxidants or
oxidizers. Put another way, the oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it's also called an
electron acceptor.
Oxidants are usually chemical substances with elements in high oxidation numbers (for example,
H2O2,
MnO4−,
CrO3, Cr
2O
72−,
OsO4) or highly
electronegative substances that can gain one or two extra electrons by oxidizing a substance (
O,
F,
Cl,
Br).
Substances that have the ability to
reduce other substances are said to be
reductive and are known as
reducing agents,
reductants, or
reducers. Put in another way, the reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it's also called an
electron donor. Reductants in chemistry are very diverse.
Metal reduction—electropositive elemental
metals can be used (Li, Na, Mg, Fe, Zn, Al). These metals donate or
give away electrons readily. Other kinds of reductants are
hydride transfer reagents (NaBH
4, LiAlH
4), these reagents are widely used in
organic chemistry, primarily in the reduction of
carbonyl compounds to
alcohols. Another useful method is reductions involving hydrogen gas (H
2) with a
palladium,
platinum, or
nickel catalyst. These
catalytic reductions are primarily used in the reduction of carbon-carbon double or triple bonds.
The chemical way to look at redox processes is that the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or
reducing agent loses electrons and is oxidized and the oxidant or
oxidizing agent gains electrons and is reduced. The pair of an oxidizing and reducing agent that are involved in a particular reaction is called a
redox pair.
Examples of redox reactions
A good example is the reaction between
hydrogen and
fluorine:
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