What is Redox reaction - explained

Redox reaction


A reaction in which reduction and oxidation both takes place is termed as redox reaction.

General introduction 

Chemistry deals with the study of composition, structure and properties of varieties of matter and the change of one kind of matter into another. This transportation if one kind of matter into another occur through different types of reactions. 

One important type of such reaction is
Reduction-Oxidation or simply Redox reaction.
Where red from reduction and ox from oxidation. All these reactions are always accompanied by energy changes in form of light, heat or electricity.

Oxidation - Reduction 

1.(a)- Oxidation

Oxidation can be defined as given below 

  • Additition of oxygen or
  • Removal of hydrogen.
  • Addition of electronegative element or
  • Removal of electropositive element

(b)- Oxidizing agent or Oxidant 

A substance which supplies oxygen or any other electronegative element, or removes hydrogen or any electropositive element.
An oxidizing agent after carring oxidation is itself reduced.


2.(a)- Reduction 

Reduction can be defined as given below.
  • Addition of hydrogen.
  • Removal of oxygen.
  •  Addition of electropositive element.
  • Removal of electronegative element.

(b)- Reducing agent or Reducant

A reducing agent or reducant may be defined as a substance which supplies hydrogen or any other electropositive element, or removes oxygen or any other electronegative element. A reducing agent after carrying out reduction is itself oxidised in a chemical reaction.

Oxidation number

As we already know that, oxidation-reduction reaction involve the transfer of electrons from one atom or ions to another. In case of ionic reactions, it's very easy to determine the total number of electrons transferred from one ion or atom to another. 

However, in many redox reactions involving covalent compound, it's not so easy to determine (1). Direction of transfer of electrons and (2). Number of electrons transferred from one reactant to the other simply by looking at the chemical equations. For eg. 

2H(2) + O(2) 👉 2H(2)O 

In this following redox reaction both reactant and products are covalent. From our knowledge of chemical bonding, we know that during the formation of H(2)O molecule, an electron pair is shared between each hydrogen and oxygen atom and that electron is not completely transferred from hydrogen to oxygen atom.

Yet in H2O molecule, O atom has higher electron density, and thus there is a partial transfer of electronic charge better called as electrons shift from hydrogen to oxygen. In other words we can easily say a cat hydrogen is is oxidized and oxygen is reduced what is said about the reaction between hydrogen and oxygen main bit true for a a number of other reactions involving covalent compounds.

With a view to identify oxidizing and reducing agents by keeping track of number another both in ionic and covalent compound and to help in balancing of equation the concept of oxidation number was introduced. 

Oxidation number of an element may be defined as a charge which an atom of the element has in its ion or or appears to have and present in the combined state with other items oxidation number are also called oxidation States.

Rules for oxidation number 

The following rules are applied to determine the oxidation number of an atom in a molecule or an ion.

1. The oxidation number of all the atom of different elements in their respective elementary States and allotropic forms is taken as zero. 
For eg :- Nitrogen, chlorine, Hydrogen, Helium sulphur, carbon, sodium, aluminium, iron etc is taken as 0. The oxidation number of each atom is zero.

2. The oxidation number of a monoatomic ion is the same as charge on it.
For eg :- oxidation number of Na+¹, mg+², al+³ lions are +1, +2, +3 respectively.

3. The oxidation number of hydrogen is +1 when combined with non metal and is -1 when combined with active metal called metal hydride such as LIH, KH, MgH(2) etc.

4. The oxidation number of oxygen is -2 in most of its compound except in peroxide like H(2)O(2), BaO(2) etc. Where it's -1. Other interesting exceptions are found in compounds : oxygen difluoride and dioxide difluoride where the oxidation state oxygen +2 and -1. This is due to the fact that chlorine being the most electronegative element known has always and oxidation number of -1

5. In compound formed by union of metal with nonmetal the metal will have positive oxidation number and and non metal will have negative oxidation number.

6. In compound formed by the union of different element the more electronegative atom will have negative oxidation number whereas the less electronegative atom will have positive oxidation number.

7. In neutral compounds the sum of oxidation number of all the atom is zero

8. In complex Ion the sum of oxidation number of all the atom in the iron is equal to the charge on the ion.

9. In polyatomic Ion the algebraic sum of the oxidation number of all the atom in iron is equal to the charge on the ion.

Note :- oxidation number in notes the oxidation state of an element in a compound.


Oxidation in term of Oxidation no.

Oxidation may be defined as a chemical change in which there occurs an increase in oxidation number of an atom or atoms.

Oxidising agent in term of oxidation no.

An oxidizing agent or an oxidant may be defined as as a substance the oxidation number of whose atom or atoms decreases.

Saints oxidizing agents are electron acceptor an acceptance of electrons case the corresponding decrease in oxidation number.

Reduction in tem of oxidation no.

Seduction may be defined as a chemical change in which there occurs a decrease in oxidation number of an atom or atoms.

Reducing agent in term of oxidation no.

A reducing agent or reductant may be defined as a substance the oxidation number of whose atom or atoms increases.

Since reducing agents are electron donors and donation of electrons case a corresponding increase in oxidation number.


Hope you all understand it easily..

Thank you for reading 

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