Editing Electrochemical cell (section)

==== Half cells ====
Galvanic cells consists of two half-cells.  Each half-cell consists of an [[electrode]] and an [[electrolyte]] (both half-cells may use the same or different electrolytes).{{cn|date=December 2024}}

The chemical reactions in the cell involve the electrolyte, electrodes, and/or an external substance ([[fuel cell]]s may use [[Hydrogen|hydrogen gas]] as a [[Reagent|reactant]]). In a full electrochemical cell, species from one half-cell lose electrons ([[Redox|oxidation]]) to their electrode while species from the other half-cell gain electrons ([[Redox|reduction]]) from their electrode.{{cn|date=December 2024}}

A ''[[salt bridge]]'' (e.g., filter paper soaked in KNO<sub>3,</sub> NaCl, or some other electrolyte) is used to ionically connect two half-cells with different electrolytes, but it prevents the solutions from mixing and unwanted side reactions. An alternative to a salt bridge is to allow direct contact (and mixing) between the two half-cells, for example in simple [[electrolysis of water]].{{cn|date=December 2024}}

As electrons flow from one half-cell to the other through an external [[Electrical network|circuit]], a difference in charge is established. If no ionic contact were provided, this charge difference would quickly prevent the further flow of electrons. A salt bridge allows the flow of negative or positive ions to maintain a steady-state charge distribution between the oxidation and reduction vessels, while keeping the contents otherwise separate. Other devices for achieving separation of solutions are porous pots and gelled solutions. A porous pot is used in the [[Bunsen cell]].{{cn|date=December 2024}}