Oxidation Half Reaction: Ca(s) à Ca2+ + 2e. Reaction 3 can be divided into oxidation and reduction half reactions. Calcium, therefore, is oxidized, or increases in charge, while gold is reduced, or decreases in charge. Six electrons are transferred from solid calcium metal to gold cations. Calcium, therefore, ranks higher in activity. In this reaction, the more reactive calcium ends up as a cation in solution, and the less reactive gold ends up as a solid. A more complete oxidation-reduction or redox reaction accounts for the transfer of electrons.ģCa(s) + 2Au3+ à 3Ca2+ + 2Au(s) Reaction 3 The electrons, however, must go somewhere. Reactions one and two, listed above, are oxidation half reactions, and show electrons leaving a solid metal sample. You will create an activity series based on these observations. Today you will combine cation solutions of metals as well as reduced (metallic) metal solids to observe their relative reactivity. More reactive, or more easily oxidized metals are found higher on the series. This relative reactivity gives rise to the activity series of metals. Calcium, therefore, is more reactive, or easily oxidized than gold, and is more likely to be found as a cation combined with another element or elements.Īu(s) à Au3+ + 3e- Less Reactive Reaction 1Ĭa(s) à Ca2+ + 2e- More Reactive Reaction 2 Calcium, on the other hand, is more readily oxidized, and does not last long in an uncombined state. You may be familiar with the fact that gold is not very reactive, meaning it does not readily give up electrons, or oxidize, making it a good choice for jewelry, some of which has preserved for millennia. Reactivity among metals is defined as the ability to lose electrons and to form a cation. Metals differ significantly in their ability to lose electrons or oxidize. Metal oxides also differ from porous iron oxides or rust, which allows for continual oxidation to thin dense oxide coatings on aluminum and chromium which protect from further oxidation to the dull grey oxides that forms on calcium or other alkali earth metals. These reactive examples are also lustrous or shiny when uncombined, however. Alkali metals, such as sodium and potassium are readily oxidized, and so are less familiar in an uncombined form. Coinage metals, such as gold and silver are readily reduced, and are found uncombined in nature. This reduced form of a metal is typified by a shiny appearance and is most likely what you think of as metallic. In their metallic or uncombined form, metals conduct both heat and electricity, and are familiar building, decorative, and conductive materials as they are both ductile and malleable. The red rock features found in the Southwest United States and Australia and the red clay found in the Southeast United States and Eastern Africa contain iron oxide deposits, or iron cations. In earth’s oxygen rich environment, however, most metals exist as cations in rocks, minerals, or dirt. Over three quarters of the known elements can be classified as metals.
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