Sunday, July 17, 2011
Manganese Is Neither Transgendered Nor Racist
The words manganese and magnesium are related. Their entwined roots stem back to a place called Magnesia in ancient Greece where they were both found in abundance. Some speculate that Spartan swords were exceptionally hard because of manganese content in their iron. Manganese's word history is parsed here and van der Krogt has his take here.
Manganese has been used since antiquity both to color and to decolorize glass. The Venetians perfected "glassmaker's soap," making high art with it. Glass always contains iron in trace amounts and this imparts a greenish "coke bottle" tinge. The addition of manganese to the molten glass produces a reddish-brown tinge which equalizes the absorption across the visible spectrum and gives so-called colorless glass. More reading on colored glass can be found here.
Manganese also demarcates an important trend in the Periodic Table. Moving from left to right across the first transition metal series, i.e., Sc -> Ti -> V -> Cr -> Mn, each element adds one more positive charge to its core (and one surrounding electron). Yet those electrons can be stripped by oxygen. A tipping point is reached between manganese and iron. Manganese is the last metal in that series to exhaustively lose all of its valence electrons to oxygen. Thus the manganese atom in permanganate MnO4-, is fully oxidized back to having an argon core. But moving just one element further to the right (to iron) is just enough change in electronegativity that iron retains two valence electrons: there is a ferrate but no perferrate.
Ironically, despite its reputation for rusting, iron retains an inner core of two valence electrons, even when completely surrounded by rapacious oxygen. Iron is one step closer to the noble metals.