The electrode that is always oxidized is the anode.
Understanding Oxidation at the Anode
Oxidation is a fundamental electrochemical process defined by the loss of electrons by a chemical species. Regardless of the type of electrochemical cell—be it an electrolytic cell or a galvanic (voltaic) cell—this crucial reaction consistently occurs at the anode.
Why Oxidation Occurs at the Anode
At the anode, species, particularly negative ions, are attracted to its surface. These ions then surrender their electrons to the electrode, resulting in their oxidation. For instance, in an electrolytic setup, the anode is deliberately made the positive electrode. This positive charge acts as a powerful magnet for negatively charged ions (anions), drawing them in to undergo electron loss.
The key aspects of oxidation at the anode include:
- Electron Loss: The defining characteristic of oxidation.
- Attraction of Anions: Negative ions (anions) are drawn to the anode's surface.
- Discharge: These anions lose electrons and are converted into neutral atoms or molecules, or ions of a higher oxidation state.
Anode Polarity: A Key Distinction
While oxidation always happens at the anode, its electrical polarity can vary depending on the type of electrochemical cell:
| Feature | Electrolytic Cell | Galvanic (Voltaic) Cell |
|---|---|---|
| Anode Polarity | Positive (+) | Negative (-) |
| Reaction Type | Non-spontaneous, driven by external power | Spontaneous, produces electrical energy |
| Electron Flow | Electrons flow away from the anode | Electrons flow away from the anode |
| Process | Anions are drawn to the positive anode, lose electrons. | The anode material itself spontaneously oxidizes, releasing electrons. |
Despite the difference in polarity, the core function of the anode remains the same: it is the site where oxidation occurs and electrons are released into the external circuit. This makes the anode an indispensable component in all electrochemical systems.
