The galvanic cell consisting of solid and oxidized zinc is a redox couple. This particular cell is referred to as the Daniell cell. The oxidized form of the element is written first, so that the redox couples in the cell are
By contrast, the reduced form of the metal is written first when the electrode is described. Thus the two bars in the Daniell cell are described as The redox reactions that occur in an electrochemical cell can be represented by a cell diagram. A cell diagram traces the path of the electrons. The reduced form of the metal to be oxidized at the anode is written first, followed by its oxidized form, then the oxidized form of the metal to be reduced at the cathode, and finally the reduced form of the metal at the cathode. The cell diagram for the Daniell cell is
Example:
Write the cell diagram for the following galvanic cell: one beaker has solid magnesium in an aqueous solution of magnesium sulfate, the other beaker has solid lead in an aqueous solution of lead sulfate. In this cell, magnesium is being oxidized.
The electrons are flowing from magnesium to lead, so the cell diagram must have the order
