Electrode
Definition and meaning of Electrode in chemistry.
Electrode refers to an electrical conductor, typically a metal, graphite, or other electron-conducting material, that makes contact with an electrolyte in an electrochemical cell to carry current into or out of solution via oxidation or reduction reactions.
In more detail
Electrodes are classified by the reaction occurring at their surface: the anode is where oxidation takes place (electrons are released into the external circuit), and the cathode is where reduction occurs (electrons are consumed). Electrodes may be active, undergoing their own chemical change as in a zinc or copper electrode, or inert, merely providing a surface for electron transfer without being consumed, as with platinum or graphite. Electrodes are central to both galvanic (voltaic) cells, which generate electrical energy from spontaneous reactions, and electrolytic cells, which use electrical energy to drive nonspontaneous reactions.
Key facts
| Field | Physical Chemistry |
|---|---|
| Anode | Site of oxidation (electron loss) |
| Cathode | Site of reduction (electron gain) |
| Common inert materials | Platinum, graphite |
In a Daniell cell, a zinc metal electrode acts as the anode (Zn oxidized to Zn2+ + 2e-) while a copper metal electrode acts as the cathode (Cu2+ + 2e- reduced to Cu), with the two half-cells connected by a salt bridge.
Frequently asked questions
What is the difference between an electrode and an electrolyte?
The electrode is the solid conductor where electron transfer occurs, while the electrolyte is the ionic solution or molten compound that carries current between electrodes through ion movement rather than electron flow.
Is the anode always the negative electrode?
No. In a galvanic (voltaic) cell the anode is negative, but in an electrolytic cell the anode is connected to the positive terminal of the external power source. In both cases, however, oxidation always occurs at the anode by definition.