Overview

Zinc is a chemical element represented by the symbol Zn and atomic number 30. As a common metal it is often called spelter in older industrial contexts. Its standard atomic mass is about 65.38. Zinc atoms contain 30 protons and 30 electrons, and the element occurs naturally in crustal minerals and in trace amounts in living organisms. For a concise treatment of its chemical classification, see the entry on chemical element and related metal groups.

Classification and physical properties

Metallic zinc is often placed among the metals of the periodic table and traditionally discussed with the transition metals, though many sources treat it as a post-transition metal because of its filled d-subshell and characteristic properties. Zinc is a moderately reactive metal that forms a dull protective oxide coating when exposed to air. It alloys readily with other metals — most notably copper to form brass — and is used in casting, plating and corrosion-resistant coatings.

Isotopes

There are around 29 known isotopes of zinc, of which five occur naturally in appreciable amounts. Some isotopes are unstable; radioactive isotopes have measured half-lives that vary greatly. For example, the proton-rich isotope 57Zn decays rapidly, while other isotopic species are effectively stable on geological time scales. Isotopic composition is useful in geochemistry and environmental studies to trace sources and cycling of zinc in ecosystems.

Occurrence, extraction and history

Zinc is most commonly extracted from sulfide ores such as sphalerite; ores are processed by roasting, leaching and electrochemical or pyrometallurgical methods to obtain the metal. Historically, metal production and use of zinc compounds go back to antiquity; metallic zinc was produced and used in several regions long before large-scale industrial extraction developed. The familiar English name "spelter" reflects early trade terminology for refined zinc metal.

Uses and applications

Zinc has a wide range of industrial and consumer applications. Key uses include:

  • Galvanizing steel to prevent corrosion — the most important single commercial use.
  • Primary and secondary batteries, including zinc–carbon and alkaline cells, and emerging zinc-based rechargeable systems.
  • Alloys (brass and various die-casting alloys), metal coatings, and castings.
  • Chemical compounds such as zinc oxide and zinc chloride used in paints, rubber, ceramics, sunscreens and as catalysts.

Biological role, safety and notable facts

Zinc is an essential trace element for humans and many other organisms. It participates in the function of numerous enzymes and structural proteins, including zinc-finger motifs that help regulate gene expression. Dietary zinc is obtained from foods such as meat, seafood, legumes and fortified products; both deficiency and excess can have health consequences, so intake is regulated by dietary guidelines. Industrial handling of zinc and its dusts requires basic safety measures to avoid inhalation, and environmental releases are managed because of zinc's ecological effects at high concentrations.

For further technical or chemical details consult specialist references or databases using the links above and related materials on elemental chemistry and metallurgy.