Manganese is a chemical element with the symbol Mn and atomic number 25. It is one of the silvery white, hard, brittle metals of Group 7 (VIIb) of the periodic table. It was recognized as an element in 1774 by the Swedish chemist Carl Wilhelm Scheele while working with the mineral pyrolusite and was isolated the same year by his associate, Johan Gottlieb Gahn. Although it is rarely used in pure form, It is essential element to steelmaking.
It is second only to iron among the transition elements in its abundance in Earth’s crust; it is roughly similar to iron in its physical and chemical properties but is harder and more brittle.
It is essential to plant growth and is involved in the assimilation of nitrates in green plants and algae. It is an essential trace element in higher animals, in which it participates in the action of many enzymes. Lack of Mn causes testicular atrophy. An excess of this element in plants and animals is toxic.
Physical and Chemical Characteristics of Manganese
- It is a silvery-gray metal that resembles iron. It is hard and very brittle, difficult to fuse, but easy to oxidize. Mn metal and its common ions are paramagnetic.
- Manganese tarnishes slowly in air and oxidizes (“rusts”) like iron in water containing dissolved oxygen.
- It burns in air or oxygen at elevated temperatures, as does iron; decomposes water slowly when cold and rapidly on heating; and dissolves readily in dilute mineral acids with hydrogen evolution and the formation of the corresponding salts in the +2 oxidation state.
- Mn is quite electropositive, dissolving very readily in dilute non oxidizing acids.
- It also combines directly with boron, carbon, sulfur, silicon, or phosphorus but not with hydrogen.
- The most important manganese compound is manganese dioxide, in which manganese is in the +4 oxidation state, and the black mineral pyrolusite is the chief source of manganese and all of its compounds. It is also widely used as a chemical oxidant in organic synthesis.