Oxidation-Reduction Balances of the Earth System

Just as was the case with acid-base interactions, numerous elements are involved in 

Oxidation-reduction reactions in water are dominated by the biological processes of photosynthesis and organic matter oxidation. A very different set of oxidation reactions occurs within the gas phase of the atmosphere, often a consequence of photochemical production and destruction of ozone (O3). While such reactions are of great importance to chemistry of the atmosphere - e.g., they limit the lifetime in the atmosphere of species like CO and CH4 - the global amount of these reactions is trivial compared to the global O2 production and consumption by photosynthesis and respiration. 

Iron Fe(II) Fe, Fe(OH)2, FeCOsfs) (ferrous ion, ferrous hydroxide, ferrous carbonate solid) 

Manganese Mn(II) Mn , MnC03(s) (manganous ion, manganous carbonate solid) 

Normally in chemistry one does not expect reaction rates or sequences to follow thermodynamic energy gain. Rather, they are dictated by 

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