Super Glossary

Zinc (Zn)

Science / Periodic Table of Elements / Zinc (Zn): Atomic number: 30, Atomic mass: 65.37 g.mol -1, Electronegativity: 1.6, Density: 7.11 g.cm-3 at 20?°C, Melting point: 420 ?°C, Boiling point: 907 ?°C, Vanderwaals radius: 0.138 nm, Ionic radius: 0.074 nm (+2), Isotopes: 10, Electronic shell: [ Ar ] 3d10 4s2, Energy of first ionisation: 904.5 kJ.mol -1, Energy of second ionisation: 1723 kJ.mol -1, Standard potential: - 0.763 V, Discovered: Andreas Marggraf in 1746. Zinc is a lustrous bluish-white metal. It is found in group IIb of the periodic table. It is brittle and crystalline at ordinary temperatures, but it becomes ductile and malleable when heated between 110?°C and 150?°C. It is a fairly reactive metal that will combine with oxygen and other non-metals, and will react with dilute acids to release hydrogen. Applications: It is used principally for galvanizing iron, more than 50% of metallic zinc goes into galvanizing steel, but is also important in the preparation of certain alloys. It is used for the negative plates in some electric batteries and for roofing and gutters in building construction. Zinc is the primary metal used in making American pennies, is used in die casting in the automobile industry. Zinc oxide is used as a white pigment in watercolours or paints, and as an activator in the rubber industry. As a pigment zinc is used in plastics, cosmetics, photocopier paper, wallpaper, printing inks etc, while in rubber production its role is to act as a catalyst during manufacture and as a heat disperser in the final product. Zinc metal is included in most single tablet, it is believed to possess anti-oxidant properties, which protect against premature aging of the skin and muscles of the body. Zinc in the environment: Zinc is a very common substance that occurs naturally. Many foodstuffs contain certain concentrations of zinc. Drinking water also contains certain amounts of zinc, which may be higher when it is stored in metal tanks. Industrial sources or toxic waste sites may cause the zinc amounts in drinking water to reach levels that can cause health problems. Zinc occurs naturally in air, water and soil, but zinc concentrations are rising unnaturally, due to addition of zinc through human activities. Most zinc is added during industrial activities, such as mining, coal and waste combustion and steel processing. Some soils are heavily contaminated with zinc, and these are to be found in areas where zinc has to be mined or refined, or were sewage sludge from industrial areas has been used as fertilizer. Zinc is the 23rd most abundant element in the Earth's crust. The dominant ore is zinc blende, also known as sphalerite. Other important zinc ores are wurzite, smithsonite and hemimorphite. The main zinc mining areas are Canada, Russia, Australia, USA and Peru'. World production exceeds 7 million tonnes a year and commercially exploitable reserves exceed 100 million tonnes. More than 30% of the world's need for zinc is met by recycling.
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