Cell notation or cell representation in chemistry is a shorthand method of expressing a reaction in an electrochemical cell. In cell notation, the two half-cells are described by writing the formula of each individual chemical species involved in the redox reaction across the cell, with all other common ions and inert substances being ignored. Each species is separated by a vertical bar, with the species in each half-cell grouped together, and the two half-cells separated by two bars or slashes representing a salt bridge (which generally contains an electrolyte solution such as possasium nitrate or sodium chloride that is left unwritten). It is common practice to represent the anode to the left of the double bar and the cathode to the right, and to put aqueous species closest to the double