Railsback's Some Fundamentals of Mineralogy and Geochemistry The multiple forms of oxygen Fully-reduced Not-fully-reduced oxygen; oxygen unstable at some time scale Mineralogists think of oxygen in Nominal its 2- oxidation state in minerals, oxidation and geochemists additionally think number -2 -1 0 about it as elemental diatomic Name of Elemental oxygen (O2) in redox geochemistry. Oxide However, that's just a beginning if state oxygen one additionally considers chemical processes in the atmosphere. As Oxide minerals Diatomic the table at right shows with its blue e.g., MgO oxygen region, atmospheric chemistry additionally deals with ozone, with Oxysalt minerals peroxide, and with oxide gases. O2 The interaction of the less-reduced e.g., CaCO3 Hydroxyl forms of oxygen with the not-fully- & MgFeSiO4 radical Ozone oxidized gases (SO2, NO, NO2, Examples 0 etc.) provides much entertainment Hydroxide minerals OH O3 in atmospheric chemistry. e.g., Al(OH) 3 Hydrogen Atomic One very important point to note here is the difference between OH, ology Hydroxide ion peroxide oxygen the highly reactive hydroxyl radical, Minera - and the hydroxide ion OH-, the OH H2O2 O entity found in water that we can Hydroperoxyl Significant think of as dissociated H2O. In the Water & its vapor in the upper table at right, the OH representing radical atmosphere the peroxide radical has a "0" H2O (>85 km) superscript to remind readers of its HO2 overall neutral charge, but most Aqueous/redox Oxide gases One O0 & authors and printers leave it simply geochemistry e.g., CO, CO , SO one O- as an unadorned "OH". Thus the 2 2 names and chemical symbols for N2O, NO, & NO2 C N OFNe OH and OH- look much alike, but Atmospheric Si P S Cl Ar the two chemical entities are very chemstry different. As Se Br Kr LBR OxygenForms04 3/2008.