In a voltaic (galvanic) cell, the anode is the electrode where oxidation occurs.
This means:
- The substance at the anode loses electrons.
- These electrons then flow through the external circuit toward the cathode.
- As a result, the chemical species at the anode is oxidized (its oxidation state increases).
In simple terms, the anode gives away electrons and is the site where the chemical reaction loses electrons.
For example, in a zinc-copper cell, zinc metal at the anode loses electrons and goes into the solution as zinc ions.
So, in a voltaic cell, the anode is always the site of oxidation.