Manganese

Manganese ([Ar]3d5 4s2) can use any number of its seven valence electrons, giving it oxidation states from −3 to +7, the widest range of any element in the first transition row. The +2 state is the most stable in water, because Mn2+ keeps a half-filled d subshell; its salts are pale pink. Manganese dioxide (+4) is a brown-black solid used in batteries, and purple permanganate (+7) is a strong oxidizing agent used to treat water and to analyze iron.

The metal itself is hard and brittle, so it is almost never used on its own. About 90 percent of manganese goes into steel, where it removes oxygen and binds sulfur as manganese sulfide, preventing the steel from cracking when it is hot-rolled. Nearly every tonne of steel contains manganese. In living things, a cluster of four manganese atoms and one calcium atom in photosystem II splits water during photosynthesis, releasing the oxygen in Earth's atmosphere.

Discovery

Black manganese oxide was used as a pigment in prehistoric cave paintings and by ancient glassmakers to remove green tints from glass. In 1774 Carl Wilhelm Scheele recognized that the mineral pyrolusite contained a new element, and that same year his colleague Johan Gottlieb Gahn isolated impure manganese by heating the oxide with carbon. The name comes, through Italian, from magnesia, the Latin name for black minerals from the Magnesia region of Greece.