Manganese oxidation states/valences

Ground-state electronic configuration is ls 2s 2p 3s 3p 3i 4s. Manganese compounds are known to exist in oxidation states ranging from —3 to +7 (Table 2). Both the lower and higher oxidation states are stabilized by complex formation. In its lower valence, manganese resembles its first row neighbors chromium and especially iron ia the Periodic Table. Commercially the most important valances are Mn, Mn ", or Mn ". ... 

As the oxidation state of manganese increases, the basicity declines, eg, from MnO to Mn20y. Oxyanions are more readily formed ia the higher valence states. Another characteristic of higher valence-state manganese chemistry is the abundance of disproportionation reactions. 

Note that the occurrence of a maximum oxidation state, corresponding to the removal of all the valence shell electrons and the adoption of a configuration, does not occur after manganese. In Chapter 9 we see how this reflects the contraction of the poorly penetrating 3d orbitals as the nuclear charge increases and it becomes progressively more difficult to remove electrons. 

Except for the elements at the ends of the rows, each transition metal can exist in several different oxidation states. The oxidation states displayed by the 3d transition metals are shown in Table 20-1. The most important oxidation states are highlighted in the table. The most common oxidation state for the 3d transition metals is +2, known for all the elements except Sc. Chromium, iron, and cobalt are also stable in the +3 oxidation state, and for vanadium and manganese the -H4 oxidation state is stable. Elements from scandium to manganese have a particularly stable oxidation state corresponding to the loss of ah the valence electrons configuration). 

Palenik, G. J. (1997c). Bond valence sums in coordination chemistry using oxidation state independent i o values. A simple method for calculating the oxidation state of manganese in complexes containing only Mn-O bonds. Inorg. Chem. 36, 4888-90. 

Table III shows the abundance of various elements in the earth s crust and the oxidation states they frequently occupy. The table indicates that of the 14 most abundant elements, only six participate in redox reactions in the surface layers of the earth. [PH3 seems to be extremely rare (42) and will not be discussed.] Because by definition free oxygen as 02 is absent in the anoxic zone, it is evident that oxides of Fe(III) are the most important oxidizers in anoxic environment and that S042 and higher oxides of manganese are of importance only locally. Reducing compounds of importance are organic matter and sulfides, the latter frequently from volcanic emanations. Hydrogen is commonly combined with other elements, as in H20, CH4, and NH3 but may locally occur free as H2. Since iron is the most widespread element that can serve as an oxidizer in the anoxic environment the distribution of the valence states of iron in various rocks is of interest (see Table IV). Sandstones frequently have a high Fe203/Fe0 ratio, but shales and clays may also be highly oxidized as shown in Tables IV and V. Since approximately 75% of the earth s surface is covered with sediments and since the sediments...

Many of the transition elements exhibit more than one valence state, resulting from the possible removal of successive electrons from the inner partially filled d subshell. These d electrons may be removed singly or in groups thus the various oxidation states of an element may differ by one unit or hy more than one unit. As examples, the important oxidation states of vanadium are +3, +4, and +5 those for chromium are +2, + 3, and +6 and those for manganese are +2, +3, +4, +6, and +7. Among families of transition metals, the higher valence states become the more stable near the bottom of each family for example, in the chromium group the stability of the +6 states decreases in the order ... 

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