Manganese and Its Congeners

The principal oxidation states of manganese are-f2,+3,+4,+6, and+7. The maximum oxidation number, +1, corresponds to the position of the element in the periodic table (group Vila). 

The principal ore of manganese is pyrolusite, Mn02 Pyrolusite occurs as a black massive mineral and also as a very fine black powder. Less important ores are braunite, MnoOa (containing some silicate) inanganite, MnO(OH) and rhodochrosite, MnCO.3. 

Impure manganese can be made by reducing manganese dioxide with carbon  

Manganese is a silvery-gray metal, with a pinkish tinge. It is reactive, and displaces hydrogen even from cold water. Its principal use is in the manufacture of alloy steel. 

Its oxidizing power also underlies its use in the ordinary dry cell (Chapter 11). 

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The congeners of manganese are very rare. The middle element of the group, technetium (Z = 43), has not been isolated from mineral sources, and there is good reason to suppose that detectable quantities do not occur naturally (Chap. 27, Exercise 7). Weighable amounts of this element and its compounds have been made from molybdenum by nuclear displacement and from uranium by nuclear fission (p. 474). Rhenium (Z =5 75) occurs naturally but in only tiny amounts. It has been estimated that there is one atom of rhenium present in the earth s crust for each two billion (2 X 109) atoms of silicon. Rhenium was discovered in 1925, technetium in 1937. 

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