Manganese (a designation deprecated by its similarity to magnesium) is a chemical element, symbol Mn, atomic number 25 (25 protons and 25 electrons) and atomic mass 55 u, solid at room temperature.

It is located in group 7 (7B) of the periodic classification of the elements, being an external transition metal. Used in alloys, mainly in steel, and also used for the production of batteries. It was discovered in 1774 by the Swedish Johan Gottlieb Gahn, reducing its oxide with carbon. Its main application is in the manufacture of metal alloys in which it is a sulphur-oxygen-removing agent and other uses of its main compounds include manganese dioxide in the manufacture of dry batteries and potassium permanganate in the laboratory as oxidizing agent in various chemical reactions.

It is the 12th most abundant element of the Earth’s crust and its main ores are pyrolusite and rhodochrosite.
The process of phosphating with manganese is used in the treatment against rust and corrosion of steel. Depending on their oxidation state, manganese ions have varying colours and are industrially used as pigments. The alkali and alkaline earth permanganates are powerful oxidants.

Manganese dioxide is used as a cathode (or electron acceptor) in standard dry cells and alkaline batteries available on the market. In biology, manganese ions function as coadjutants to a wide variety of enzymes that perform many functions. Manganese enzymes are particularly essential in the process of detoxifying superoxide free radicals in organisms that need to make use of elemental oxygen. Manganese also works in the oxygen-releasing complex of photosynthetic plants. The element is a mineral required in minute quantities for all known living organisms.