DECEMBER, 1951
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A LECTURE REPRESENTATION OF OXIDATION-REDUCTION R. T. SANDERSON State University of Iowa, Iowa City, Iowa
MANYstudents of elementary chemistry have difficulty in understanding the concept of oxidationreduction, even in its simplest application to reactions mhich actually form ions. I n particular, it seems hard for them to comprehend that by the process of acting as an oxidizing agent, an atom becomes a reducing agent, and vice versa, and that whether or not an atom or ion will act as a reducing agent or oxidizing agent or neither depends on relative attractions for electrons. A very helpful demonstration of oxidation-reduction by electron transfer can he presented with the aid of a few permanent magnets, of progressively increasing strengths, to represent atoms of oxidizing agents, and an iron object t o represent an electron. For example, suppose one has four magnets, differing in strength, the strongest representing an atom of fluorine, the next strongest representing an atom of chlorine, the next an atom of bromine, and the weakest an atom of iodine. One may first demonstrate that each atom is capable of taking on an electron, and thus acting as an oxidizing
agent, by showing that each of the magnets can pick up a nail representing the electron. Pointing out that any atom mhich has taken on an electron can give it up again, thus acting as a reducing agent, one can then demonstrate that the iodine magnet, after taking on an electron to become an iodide ion, can give up the electron to the bromine, chlorine, and fluorine magnets. Similarly, one can show that the fluorine and chlorine magnets but not the iodine magnet can take an electron away from the hromine magnet, and that only the fluorine magnet can take the electron away from the chlorine magnet. In such a manner the relative oxidizing strengths of the halogen atoms and the relative reducing strengths of the halide ions can be demonstrated by an analogy which is easy for the student to understand and to extend to oxidation-reduction reactions in general. Magnets can easily he adjusted to the desired relative strengths by gluing a very few thicknesses of thin paper or Scotch tape over the ends.
