- Manganese (Mn) is a hard, brittle, silvery-gray transition metal with atomic number 25, positioned in Group 7 of the periodic table.
- It has seven valence electrons—two in the 4s subshell and five in the 3d subshell—and exhibits oxidation states from −3 to +7, with +2, +4, and +7 being the most common in stable compounds. Its atomic structure consists of twenty-five protons, typically thirty neutrons, and twenty-five electrons arranged in four shells.
- Naturally occurring manganese is composed of a single stable isotope, manganese-55 (⁵⁵Mn), though several radioactive isotopes are known and used in research.
- Manganese is the twelfth most abundant element in Earth’s crust, making up about 0.10% by weight. It is not found in its pure metallic form in nature due to its reactivity but occurs in many minerals, including pyrolusite (MnO₂), rhodochrosite (MnCO₃), and manganite (MnO(OH)). The largest manganese reserves are located in South Africa, followed by Ukraine, Australia, Brazil, and India. Pyrolusite is the primary commercial ore, mined extensively for metallurgical and chemical uses.
- The element was first recognized in 1774 by Swedish chemist Carl Wilhelm Scheele, who studied pyrolusite and showed it contained a new element. The same year, his colleague Johan Gottlieb Gahn successfully isolated manganese metal by reducing manganese dioxide with carbon. The name “manganese” comes from the Italian manganese, itself derived from the Latin magnes, meaning “magnet,” due to the magnetic properties of some manganese-containing minerals.
- Manganese is essential to the steel industry, where it is primarily used as an alloying element and deoxidizing agent. Adding manganese to steel improves its strength, hardness, and wear resistance while also counteracting the brittleness caused by sulfur impurities. High-manganese steels, such as Hadfield steel (containing around 12% manganese), are exceptionally tough and wear-resistant, making them suitable for railroad tracks, prison bars, and mining equipment.
- In addition to steelmaking, manganese compounds have significant industrial applications. Manganese dioxide (MnO₂) is used in dry-cell batteries (such as alkaline and zinc-carbon cells) as a depolarizer. Potassium permanganate (KMnO₄), with manganese in the +7 oxidation state, is a powerful oxidizing agent used in water treatment, disinfection, and organic synthesis. Manganese compounds are also used in pigments, fertilizers, and ceramics.
- Chemically, manganese is versatile, forming compounds across a wide range of oxidation states. Mn²⁺ compounds are typically pale pink, Mn⁴⁺ compounds are dark brown or black, and MnO₄⁻ ions are deep purple. Manganese metal oxidizes slowly in air, forming a surface oxide layer, and reacts readily with acids, releasing hydrogen gas.
- Biologically, manganese is an essential trace element for humans, plants, and animals. It plays a crucial role in enzyme activation, metabolism, bone formation, and antioxidant defense through the enzyme manganese superoxide dismutase (MnSOD). Deficiency in humans is rare but can impair growth, reproductive health, and metabolism. However, excessive exposure to manganese dust or fumes—particularly in occupational settings like mining and welding—can cause a neurological disorder known as manganism, with symptoms similar to Parkinson’s disease.
- Environmentally, manganese is generally considered safe in natural concentrations, but mining and industrial discharges can elevate levels in water and soil. High environmental concentrations can impact ecosystems, particularly aquatic life, by disrupting physiological processes.
