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Chemistry of Zinc

  • Page ID
    31652
  • The name for zinc is of German origins, zink. It has been known since pre-historic times and compounds as well as the metal had been used for many years before anyone ever thought about elements at all! Zinc (Zn) is a blue-white metal of moderate strength, hardness and ductility. Zinc is one of the least common elements and is mostly produced through electrolysis of aqueous zinc sulfate. About one third of all metallic zinc is used to manufacture galvanized nails. Because of its low melting point and its ability to form bonds with iron or steel, it serves to coat the metal and protect it from corrosion. Metallic zinc is also used to make dry cell batteries.

    Physical Properties

    Pure zinc is a bluish-silver and ductile metal with a low melting and boiling point. Most zinc today is obtained from ZnS, extracted from zinc blende ore and roasted to remove the sulfur. Zinc can also be obtained by electrolysis of aqueous zinc sulfate, a common laboratory exercise.

    Figure 1: Brass die, along with zinc and copper samples. Image used with permission from Wikipedia
    Zinc plays a huge part in the production of alloys. One of the best known zinc alloy is brass, which contains between 55-95% copper. Zinc also takes part in manufacturing solder, which has a relatively low melting point. Solder is used to join electrical components, as well as pipes and other metals.

    Chemistry Properties

    Zinc is reasonably resistant to corrosion and is used as a covering for baser metals like iron ("galvanizing"). Zinc can be readily cast or molded. Zinc has many unique characteristics. For example, its vapor burns in air with a green flame, forming zinc oxide. Zinc oxide is a common zinc compound that is used in paints, cosmetics, plastics and more. Metallic zinc reacts with weak acids very slowly. Sulfur has a strong affinity for zinc. When heated, the two powders react explosively to form zinc sulfide. Zinc sulfide is used to make television screens and fluorescent light bulbs.

    Zinc also reacts with halogens. However, as the electronegativity decreases among the halogen group, the reactivity with zinc decreases. Thus, the most electronegative of the halogens (Fluorine) reacts with zinc violently, while the less electronegative halogen (Iodine) only generates a small amount of heat. Interestingly, properties of zinc are strongly affected by impurities such as lead, cadmium and iron. Also, zinc is most often used as a reducing agent in chemical reactions and it forms complex ions with ammonia and cyanide ions.

    References

    1. Gorodetsky, Malka; Singerman, Ammon. "Electroforming: An improvised experiment on electroplating." J. Chem. Educ.1980, 57, 514.

    Contributors

    • Tabatha Schnelker
    • Stephen R. Marsden (ChemTopics)