Redox Chemistry of Nonmetals
Oxidizing Abilities of NonmetalsWhen nonmetallic elements act as oxidizing agents, the nonmetal is reduced to its monatomic anion or a protonated form.
The monatomic nonmetal anions and their protonated forms usually exhibit the lowest possible oxidation number which gives them the ability to transfer electrons back to other materials (act as reducing agents).
Nonmetals can be divided into two groups based on their redox properties.
Sulfur serves as an oxidizing agent for some electronegative metals. For example, the tarnishing of silver is the formation of silver sulfide.
The electonegative nonmetals have moderate to strong reducing properties.
Basic Behavior of Nonmetal Anions
Periodic Trends in the basicitiy and reducing ability of monoatomic anions:
Periodic trends in the acidity of protonation monoatomic anions:
Pseudohalide IonsPseudohalide ions are polyatomic anions that resemble halide ions in both their acid-base and redox chemistry. Like the halide ions, they have relatively low basicity generally falling in the feebly to moderately basic categories.
The oxidation of the cyanide, thiocyanate and thiosulfate ions generates dimeric species analogously to the oxidation of the halogens.
Azide is a powerful reducing agent that will even reduce the sodium ion. Sodium azide produces sodium metal on heating.
Hydride (H-) is both a powerful base and a powerful reducing agent.
Explosives, Flammability and Strong Oxidizing AgentsCompounds which are in very high oxidation states such as oxo anions or oxo acids and elements in very low oxidation states rarely have overlapping predominance areas in Pourbaix diagrams. Therefore they tend to react with each other. These reactions are often extremely exothermic giving off more energy than acid base reactions.
Often reactions between species with nonoverlapping predominance areas do not occur immediately because of a high energy of activation. The reaction between strong oxidizing and strong reducing agents often requires an initiator such as a catalyst or source of energy such as a spark. Once initiated, these exothermic reactions may occur so rapidly that a fire or explosion results.