Definition+3

Oxidation is the loss of electrons .

When you reach Definition 4, you will realise that the gain or loss of electrons may not be truly the best definition for redox.

This third definition is best used in situations whereby equations are written in ionic form.

__Example 1__ Zn + Cu 2+ → Zn 2+ + Cu Zinc is more reactive than copper, thus zinc displaces copper(II) ions from its aqueous solution. Details of such displacement will be introduced in the chapter on Metals.

Based on atomic structure, each Zn atom will lose two valence electrons to form the octet, stable structure, Zn 2+ . Thus, Zinc has been ** oxidised ** to form Zn 2+ . The substance playing the role of the oxidising agent is Cu 2+ .

__Example 2__ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">2Fe <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">3+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> + H <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">S → 2Fe <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">2+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> + 2H <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> + S <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">Fe <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">3+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> gains one electron to form Fe <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">2+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">. Thus, Fe <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">3+ <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> has been reduced and H <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">S is the reducing agent.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">But how do we use this definition if the equation is not an ionic, but a chemical balanced equation? <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Then we will have to interpret the substance by "looking into the formula".

<span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">__Example 3__ <span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">Cl <span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">(g) + 2KI(aq) → 2KCl(aq) + I <span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">(aq) <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;"> <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">at this point, we will have to apply our knowledge of atomic structure and bonding before we can decide what happen to the reactants. <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">for Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">, two chlorine atom share their valence electrons to form a chlorine molecule. <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">for Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> to become Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">- <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> in KCl, Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> has to gain 2 electrons to form 2Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: super;">- <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">. <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;">Thus Cl <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif; vertical-align: sub;">2 <span style="color: #810081; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> has been reduced and KI is the reducing agent. Read this link which summarises the three definitions of oxidation. []

<span style="color: #008000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">the following video will help you to understanding more about gain and loss of electrons.

<span style="color: #0000ff; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 120%;">[[media type="youtube" key="a6RR4kPsnlE" height="344" width="425"]]