Manganese ( ) is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals. As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

Manganese ions have various colors, depending on their oxidation state, and are used industrially as pigments. The permanganates of sodium, potassium and barium are powerful oxidisers. Manganese dioxide is used as the cathode (electron acceptor) material in standard and alkaline disposable dry cells and batteries.

Manganese(II) ions function as cofactors for a number of enzymes in higher organisms, where they are essential in detoxification of superoxide free radicals. The element is a required trace mineral for all known living organisms. In larger amounts, and apparently with far greater activity by inhalation, manganese can cause a poisoning syndrome in mammals, with neurological damage which is sometimes irreversible.

Physical

Manganese is a gray–white metal, resembling iron. It is a hard metal and is very brittle, fusible with difficulty, but easily oxidized. Manganese metal and its common ions are paramagnetic. While manganese metal does not form a permanent magnet, it does exhibit strong magnetic properties in the presence of an external magnetic field.

Occurrence

See also manganese minerals.

Manganese makes up about 1000 ppm (0.1%) of the Earth's crust, making it the 12th most abundant element there. Soil contains 7–9000 ppm of manganese with an average of 440 ppm. Seawater has only 10 ppm manganese and the atmosphere contains 0.01 µg/m³.

Manganese occurs principally as pyrolusite (MnO₂), braunite, (Mn²⁺Mn³⁺₆)(SiO₁₂), psilomelane (Ba,H₂O)₂Mn₅O₁₀, and to a lesser extent as rhodochrosite (MnCO₃). Land-based resources are large but irregularly distributed. Over 80% of the known world manganese resources are found in South Africa and Ukraine. Other important manganese deposits are in China, Australia, Brazil, Gabon, Ghana, India, and Mexico.

Vast quantities of manganese exist in manganese nodules on the ocean floor. Attempts to find economically viable methods of harvesting manganese nodules were abandoned in the 1970s.

Isotopes

Main: Isotopes of manganese Naturally occurring manganese is composed of 1 stable isotope; ⁵⁵Mn. 18 radioisotopes have been characterized with the most stable being ⁵³Mn with a half-life of 3.7 million years, ⁵⁴Mn with a half–life of 312.3 days, and ⁵²Mn with a half–life of 5.591 days. All of the remaining radioactive isotopes have half lives that are less than 3 hours and the majority of these have half lives that are less than 1 minute. This element also has 3 meta states.