Transition metal
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny blue whitish appearance when surface oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. Zinc is the 24th most abundant element in Earth's crust, with an average concentration of 70 grams per ton. Zinc also has five stable isotopes; the most abundant of which, Zn-64, comprises nearly half of zinc's total abundance. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest concentration of economically feasible lodes in descending order are located in China, Peru, and Australia, among others. Zinc is refined industrially by froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).
Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for both prenatal and postnatal development. It is the second most abundant trace metal in humans after iron, an important cofactor for many enzymes, and the only metal which appears in all enzyme classes. Zinc is also an essential nutrient element for coral growth.
Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans. …
Various isolated examples of the use of impure zinc in ancient times have been discovered. Zinc ores were used to make the zinc–copper alloy brass thousands of years prior to the discovery of zinc as a separate element. Judean brass from the 14th to 10th centuries BC contains 23% zinc.
Knowledge of how to produce brass spread to Ancient Greece by the 7th century BC, but few varieties were made. Ornaments made of alloys containing 80–90% zinc, with lead, iron, antimony, and other metals making up the remainder, have been found that are 2,500 years old. A possibly prehistoric statuette containing 87.5% zinc was found in a Dacian archaeological site.
Strabo writing in the 1st century BC (but quoting a now lost work of the 4th century BC historian Theopompus) mentions "drops of false silver" which when mixed with copper make brass. This may refer to small quantities of zinc that is a by-product of smelting sulfide ores. Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.
The manufacture of brass was known to the Romans by about 30 BC. They made brass by heating powdered calamine (zinc silicate or carbonate), charcoal and copper together in a crucible. The resulting calamine brass was then either cast or hammered into shape for use in weaponry. Some coins struck by Romans in the Christian era are made of what is probably calamine brass.
The oldest known pills were made of the zinc carbonates hydrozincite and smithsonite. …
Zinc is a bluish-white, lustrous, diamagnetic metal, though most common commercial grades of the metal have a dull finish. It is somewhat less dense than iron and has a hexagonal crystal structure, with a distorted form of hexagonal close packing, in which each atom has six nearest neighbors (at 265.9 pm) in its own plane and six others at a greater distance of 290.6 pm. The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C. Above 210 °C, the metal becomes brittle again and can be pulverized by beating. Zinc is a fair conductor of electricity. For a metal, zinc has relatively low melting (419.53 °C) and boiling point (907 °C). This melting point is the lowest of all the d-block metals aside from mercury and cadmium. For this reason among others, zinc, cadmium, and mercury are often not considered to be transition metals like the rest of the d-block metals.
Many alloys contain zinc, the most famous example being brass. Other metals long known to form binary alloys with zinc are aluminium, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium, and sodium. Although neither zinc nor zirconium is ferromagnetic, their alloy, ZrZn2, exhibits ferromagnetism below 35 K.
Zinc makes up about 70 ppm (0.007%) of Earth's crust in mass, making it the 24th-most abundant crustal element. It also makes up 312 ppm of the Solar System, where it is the 22nd most abundant element. …
Zinc makes up about 70 ppm (0.007%) of Earth's crust in mass, making it the 24th-most abundant crustal element. It also makes up 312 ppm of the Solar System, where it is the 22nd most abundant element. Typical background concentrations of zinc do not exceed: 1 μg/m3 in atmosphere, 300 mg/kg in soil, 100 mg/kg in vegetation, 20 μg/L in freshwater, and 5 μg/L in seawater. The element is normally found in association with other base metals such as copper and lead in the form of ores. Zinc is a chalcophile, meaning the element is more likely to be found associated with sulfur and other heavy chalcogens, rather than with the light chalcogen oxygen or with non-chalcogen electronegative elements such as the halogens. Sulfides formed as the crust solidified under the highly reducing conditions of the young Earth's atmosphere. Sphalerite, a crystalline form of zinc sulfide, is the most heavily mined zinc-containing ore as it contains 60–62% zinc by mass.
Other source minerals for zinc include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate). With the exception of wurtzite, all the other minerals were formed by weathering of the primordial zinc sulfides.
Currently identified zinc resources across the globe total 1.9–2.8 billion tonnes. Large deposits are in Australia, China, Canada, and the United States, with the largest potential reserves in Iran. …
Various isolated examples of the use of impure zinc in ancient times have been discovered. Zinc ores were used to make the zinc–copper alloy brass thousands of years prior to the discovery of zinc as a separate element. Judean brass from the 14th to 10th centuries BC contains 23% zinc.
Knowledge of how to produce brass spread to Ancient Greece by the 7th century BC, but few varieties were made. Ornaments made of alloys containing 80–90% zinc, with lead, iron, antimony, and other metals making up the remainder, have been found that are 2,500 years old. A possibly prehistoric statuette containing 87.5% zinc was found in a Dacian archaeological site.
Strabo writing in the 1st century BC (but quoting a now lost work of the 4th century BC historian Theopompus) mentions "drops of false silver" which when mixed with copper make brass. This may refer to small quantities of zinc that is a by-product of smelting sulfide ores. Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.
The manufacture of brass was known to the Romans by about 30 BC. They made brass by heating powdered calamine (zinc silicate or carbonate), charcoal and copper together in a crucible. The resulting calamine brass was then either cast or hammered into shape for use in weaponry. Some coins struck by Romans in the Christian era are made of what is probably calamine brass.
The oldest known pills were made of the zinc carbonates hydrozincite and smithsonite. …
Five stable isotopes of zinc occur in nature, with 64Zn being the most abundant isotope (49.17% natural abundance). The other isotopes found in nature are 66Zn (27.73%), 67Zn (4.04%), 68Zn (18.45%), and 70Zn (0.61%).
Several dozen radioisotopes have been characterized. 65Zn, which has a half-life of 243.66 days, is the least active radioisotope, followed by 72Zn with a half-life of 46.5 hours. Zinc has 10 nuclear isomers, of which 69mZn has the longest half-life, at 13.75 hours. The superscript m indicates a metastable isotope, whose nucleus is in an excited state and which will eventually return to its ground state, through the emission of excess energy in the form of one or more photons (gamma rays), with the nucleus decaying to the ground state by the end of the process.
The most common decay mode of a radioisotope of zinc with a mass number lower than 66 is electron capture. The resulting decay product will be an isotope of copper.
n30Zn + e− → n29Cu + νe
The most common decay mode of a radioisotope of zinc with a mass number higher than 66 is beta decay (β−), producing an isotope of gallium.
n30Zn → n31Ga + e− + νe
Zinc is an essential trace element for humans and other animals, for plants and for microorganisms. Zinc is required for the function of over 300 enzymes and 1000 transcription factors, and is stored and transferred in metallothioneins. It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all enzyme classes.
In proteins, zinc ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.
Roughly 2–4 grams of zinc are distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye. Semen is particularly rich in zinc, a key factor in prostate gland function and reproductive organ growth.
Zinc homeostasis of the body is mainly controlled by the intestine. Here, ZIP4 and especially TRPM7 were linked to intestinal zinc uptake essential for postnatal survival.
In humans, the biological roles of zinc are ubiquitous. It interacts with "a wide range of organic ligands", and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. …