The Reactivity Series

Oxidation and Reduction.

What is Oxidation and What is Reduction?

Oxidation means losing electrons
and reduction means gaining electrons.

In the reaction between iron and copper(II) sulfate

Fe(s)  +  Cu2+(aq)   arrow   Fe2+(aq)  +  Cu(s)

Iron metal (Fe(s)) loses 2 electrons to form iron ions (Fe2+(aq))
Fe(s)  -  2e-(aq)   arrow   Fe2+(aq)
This is called oxidation. Iron is said to be oxidised.

Copper ions (Cu2+(aq)) gain 2 electrons to form copper metal (Cu(s))
Cu2+(aq)  +  2e-(aq)   arrow   Cu(s)
This is called reduction. Copper is said to be reduced.


To help you to remember that oxidation means losing electrons
and reduction means gaining electrons,
remember  O I L R I G
(Oxidation Is Loss, Reduction Is Gain - of electrons).

Oxidation and reduction always occur together.
They are called redox reactions
(pronounced "reed - ox" for reduction / oxidation).

Oxidation may also be defined as gaining oxygen
and reduction defined as losing oxygen.
For example, when copper(II) oxide is heated with carbon

copper(II) oxide + carbon  arrow    copper + carbon dioxide.
2CuO(s)      +     C(s)    arrow      2Cu(s)     +    CO2(g)

Carbon is oxidised by gaining oxygen to form carbon dioxide.
Copper (in CuO) is reduced by losing oxygen to form
copper metal.
Note that copper has changed from Cu2+ (in CuO) to Cu(s)
and so has gained electrons.
Cu2+(aq)  +  2e-(aq)   arrow   Cu(s)

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