An Overview of Metal Ion Chemistry

Metals, like many of the elements discussed in previous chapters, can exist in nature in several different oxidation states. When bonded to other 

Detroit River (import from Upper Lakes) — 1640 630 5220 

Mass median diameters determined by centrifugal sedimentation. 

Metals exist in nature primarily in positive oxidation states, and many form stable com-poimds in more than one oxidation state. The formal oxidation number of the most common form can range from -t-1 to +6. The stable form in a given environment depends on the oxidation potential and chemical composition of that environment. Often the stable form at the Earth s surface in the presence of molecular 

Thermodynamically, virtually all metals in the elemental form are unstable with respect to redox reactions in environments where they are exposed to air and water, i.e., virtually all environments where they are used. Those metals least likely to oxidize (corrode) were long ago given the distinguished title noble metals. Efforts to prevent metals from corroding, and the cost of repairing and replacing metal structures that have done so, runs into the billions of dollars annually. Thus, one characteristic feature of the society s use of metals is that the metals are continuously, albeit slowly, degrading to a less useful form from the moment they are put into use. 

Metals, like many of the elements discussed in previous chapters, can exist in nature in several different oxidation states. When bonded to other elements, metal ions are almost always assigned a positive oxidation number and are somewhat electrophilic. Because of this, they are stabilized by association with electron-rich atoms. In particular, atoms that have a free electron pair can donate some of their electron density to the metal to form a bond. The most common and environmentally important donor atoms are oxygen, nitrogen, and sulfur. The bonds they form with metal ions range in strength from relatively weak associations such as those between a dissolved metal ion and water to very strong covalent bonds. These types of bonds are significant in both aqueous phase reactions and in the formation of insoluble compounds. 

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