Cell notation or cell representation in

chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

is a shorthand method of expressing a reaction in an

electrochemical cell An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic o ...

. In cell notation, the two half-cells are described by writing the formula of each individual

chemical species A chemical species is a chemical substance or ensemble composed of chemically identical molecular entity, molecular entities that can explore the same set of molecular energy levels on a characteristic or delineated time scale. These energy levels ...

involved in the

redox reaction Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

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 In electrochemistry, a salt bridge or ion bridge is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. It maintains electrical neutrality within the int ...

(which generally contains an

electrolyte solution An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

such as possasium nitrate or sodium chloride that is left unwritten). It is common practice to represent the

anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...

to the left of the double bar and the

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...

to the right, and to put aqueous species closest to the double bar. Cell notation may be used to represent other information that is not essential to the reaction but still useful to include. For example, the electrode's species may be marked by a

degree symbol The degree symbol or degree sign, , is a typographical symbol that is used, among other things, to represent degrees of arc (e.g. in geographic coordinate systems), hours (in the medical field), degrees of temperature or alcohol proof. The symbo ...

. The standard abbreviations for the phases of each species are often included as subscripts, in a manner similar to the notation in

chemical equations A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and chemical formulas. The reactant entities are given on the left-hand side and the product entities on the right-hand side with a plus sign between t ...

. Sometimes, the initial concentrations of dissolved species may be written to the right in parentheses (see example below). Some examples of this notation are: : This means that the left electrode (anode) is made of zinc, while the other one (right, cathode) is composed of a silver wire covered by a silver chloride layer which is not soluble. Both of the electrodes are immersed into aqueous media where zinc and chloride ions are present.Bard, A. J. and Faulkner, L. R. "Electrochemical methods. Fundamentals and applications", John Whiley & Sons, Inc, 2nd edition, USA, 2001 : This cell is very famous: the

Daniell cell The Daniell cell is a type of electrochemical cell invented in 1836 by John Frederic Daniell, a British chemist and meteorologist, and consists of a copper pot filled with a copper (II) sulfate solution, in which is immersed an unglazed earthenw ...

. If the electrodes are connected, a spontaneous reaction takes place. Zinc is oxidized, and copper ions are reduced. Sometimes the state of each species into the cell is written. For example, in the zinc cell (shown above), we can write that zinc, silver and silver chloride are solids, while zinc cation and chloride anion are in aqueous medium. So, the new notation will be: : It is possible to express the ion concentration too. For example, in the Galvanic cell: : In this case, all ions (sulfate, zinc and copper) are in a concentration equal to 1 mol/L.

References

Electrochemistry {{Electrochem-stub