Question

explain this reaction

Answer 1

In cathode cu gains 2 electrons so become negative charge. In anode the cu loses 2 electrons so become positive charge.

Answer 2

Oxidation is defined as loss of electrons. This causes increase in oxidation number.
Reduction is defined as gain of electrons. This causes decrease in oxidation number.

When copper loses electrons it is said to be oxidised. The oxidation state changes from zero to +2.
The oxidation reaction is:
Cu → Cu2+ + 2e-

When copper ion gains electrons it is said to be reduced. The oxidation state changes from +2 to 0.
The reduction reaction is:
Cu2+ + 2e- → Cu

Hope this will help u... :-)