- Zinc (Zn) is a bluish-white, lustrous, moderately reactive metal with atomic number 30, positioned in Group 12 of the periodic table.
- It has twelve valence electrons—two in the 4s subshell and ten in the 3d subshell—and almost exclusively exhibits an oxidation state of +2, though the +1 state occurs rarely in specialized compounds. Its atomic structure consists of thirty protons, typically thirty-five neutrons, and thirty electrons arranged in four shells.
- Naturally occurring zinc consists of five stable isotopes: zinc-64 (⁶⁴Zn, 48.63%), zinc-66 (⁶⁶Zn, 27.90%), zinc-67 (⁶⁷Zn, 4.10%), zinc-68 (⁶⁸Zn, 18.75%), and zinc-70 (⁷⁰Zn, 0.62%).
- Zinc is the 24th most abundant element in Earth’s crust, occurring at about 70 parts per million. It is not found in its native metallic form under natural conditions but occurs mainly in the mineral sphalerite (ZnS), which is the primary ore, as well as in smithsonite (ZnCO₃), hemimorphite (Zn₄Si₂O₇(OH)₂·H₂O), and franklinite (ZnFe₂O₄). The largest producers of zinc include China, Peru, Australia, India, and the United States.
- Zinc has been used by humans for millennia, though often unknowingly in the form of brass—an alloy of copper and zinc—dating back to at least the 1st millennium BCE. Metallic zinc was first isolated in India by the 12th century CE and in Europe by the 18th century. The name “zinc” likely originates from the German word Zink, meaning “point” or “tooth,” possibly referring to the pointed crystals that form during zinc smelting.
- Zinc’s most important industrial use is in galvanization—the process of coating steel or iron with a thin layer of zinc to prevent corrosion. This protective action occurs through both a physical barrier effect and sacrificial anodic protection, where zinc preferentially oxidizes in place of the underlying metal. Galvanized steel is widely used in construction, automotive manufacturing, infrastructure, and household appliances.
- Zinc alloys also have significant applications. Brass (copper–zinc) is used in musical instruments, plumbing fixtures, and decorative items; zinc–aluminum alloys are employed in die casting for automotive and machinery parts; and zinc is used in making coins, roofing materials, and batteries, notably zinc–carbon and zinc–air cells. Zinc oxide (ZnO) is an important compound with uses in rubber vulcanization, ceramics, glass, paints, and as a UV filter in sunscreens and cosmetics.
- Chemically, zinc is amphoteric, reacting with acids to release hydrogen gas and with strong bases to form zincates. It readily tarnishes in moist air, forming a thin layer of basic zinc carbonate that slows further corrosion. Zinc(II) compounds are typically white and diamagnetic, with important roles in pigments, catalysts, and chemical synthesis.
- Biologically, zinc is an essential trace element for all known forms of life. In humans, it is a cofactor in over 300 enzymes involved in DNA synthesis, cell division, protein metabolism, and immune function. The body contains 2–3 grams of zinc, concentrated in muscles, bones, skin, and the retina. Dietary zinc deficiency can cause impaired growth, immune dysfunction, skin lesions, and hair loss, while excessive intake can lead to nausea, vomiting, and interference with copper metabolism.
- Environmentally, zinc is generally not highly toxic in low concentrations, but excessive levels from mining, smelting, or industrial runoff can harm aquatic ecosystems and soil quality. Recycling of zinc, particularly from galvanized steel and batteries, is both technically feasible and economically important, reducing environmental impact and conserving natural resources.
