Redox Reactions in Terms of Electron Transfer Reactions

NCERT Reference: Chapter 7 – Redox Reactions– Page 128 (Part I)

Quick Notes

Oxidation = loss of electrons
Reduction = gain of electrons
Redox reactions = electron transfer between species
Example: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
- Zn is oxidized (loses 2e⁻)
- Cu²⁺ is reduced (gains 2e⁻)
Electron transfer underpins many chemical, biological, and industrial processes.
Competitive electron transfer: a more reactive metal displaces a less reactive metal from its salt solution.

Full Notes

The electron transfer concept offers a modern and universal way of understanding redox (reduction–oxidation) reactions. It’s especially useful in reactions where oxygen or hydrogen aren’t obviously involved.

Redox in Terms of Electrons

Oxidation is defined as the loss of electrons.

Reduction is defined as the gain of electrons.

A redox reaction involves the transfer of electrons from one substance to another.

Oxidising agent: electron acceptor
Reducing agent: electron donor

This idea applies broadly – whether the reaction involves ions, molecules, or more complex compounds.

For Example:

Electron transfer: Zn gives electrons to Cu2+; Zn is oxidized to Zn2+ and Cu2+ is reduced to Cu.

Zinc loses two electrons and becomes Zn²⁺ = oxidation
Copper ion gains two electrons and becomes Cu = reduction

Electrons move from Zn to Cu²⁺. This shows that oxidation and reduction always happen together — they’re part of a single process.

The pairs Zn/Zn²⁺ and Cu²⁺/Cu are known as redox couples.

Competitive Electron Transfer Reactions

Some redox reactions involve a kind of “competition” between metals to gain or lose electrons. This helps us rank metals by their reactivity – shown in the activity series.

Activity Series of Metals

Different metals have different tendencies to lose electrons and form cations.
Metals higher in the series are more reactive – they lose electrons more easily.
Such a metal can displace a less reactive one from its salt solution.

Example 1 Displacement of Cu by Zn

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

Zinc placed in copper sulfate solution deposits copper; zinc dissolves to give Zn2+.

Zn → Zn²⁺ + 2e⁻ (oxidation)
Cu²⁺ + 2e⁻ → Cu (reduction)

Example 2 Displacement of Ag by Cu

Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)

Copper wire in silver nitrate solution forms silver crystals; copper goes into solution as Cu2+.

Cu → Cu²⁺ + 2e⁻ (oxidation)
Ag⁺ + e⁻ → Ag (reduction)

These examples help us understand:

Which direction electrons move in a redox reaction
Which metals are stronger reducing agents
How to predict if a redox reaction will occur

You can think of it as a kind of electron tug-of-war, where the stronger metal pulls the electrons away from the weaker one.

Summary

Oxidation is loss of electrons.
Reduction is gain of electrons.
Every redox process has simultaneous oxidation and reduction.
Activity series shows how easily metals lose electrons and can be used to predict outcomes of displacement reactions.