When zinc metal placed in CuSO₄ solution, following reaction take place:
Zn_(s)  +  CuSO_4(aq) ZnSO_4(aq)  +  Cu_(s)

Oxidation:   Zn_(s) Zn⁺² + 2e^-1
Reduction:  Cu⁺² + 2e^-1 Cu
Overall:      Zn_(s) + Cu⁺² Zn⁺² + Cu_(s)
 
 

Electrons will not flow in the following apparatus:

But if  reaction carried out in the apparatus shown in Figure 21.2 (Cu/Ag system), electrons are transferred from Zn° to Cu⁺² through a wire producing electrical energy.

The salt bridge is necessary to complete the circuit and maintain charge neutrality.
Zn⁺²  cathode
SO₄^-2  anode
 

Anode	Cathode
Oxidation occurs	Reduction occurs
Eectrons produced	Electrons are consumed
Anions migrate toward	Cations migrate toward
Has negative sign	Has positive sign

Shorthand Notation for:
Zn° + Cu⁺²Zn⁺² + Cu°

 
 
 
 

Example
Write shorthand notation for:   Fe_(s) + 2Fe⁺³_(aq) 3Fe⁺²_(aq)
Fe^°Fe⁺²Fe⁺³Fe⁺²

Write shorthand notation for:   2Ag⁺¹_(aq)  +  Ni_(s) 2Ag_(s) + Ni⁺²_(aq)
Ni^°Ni⁺²Ag⁺¹Ag^°