Manganese (Mn) is a metallic chemical element with atomic number 25. Its only stable isotope is 55Mn, with 25 protons and 30 neutrons.
One of the uses of manganese is that it's often included in steel alloys. In nature, manganese if primarily found in the form of manganese dioxide (MnO2). Manganese dioxide can be used in batteries, and it is also used as a pigment in glass and ceramics. It has even been used as paint in prehistoric cave paintings.