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Zinc, 30Zn
Zinc fragment sublimed and 1cm3 cube.jpg
Zinc
Appearancesilver-gray
Standard atomic weight Ar, std(Zn)65.38(2)[1]
Zinc in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a blue-silvery appearance when oxidation is removed. It is the first element in group 12 of the periodic table. 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. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).

Brass, an alloy of copper and zinc in various proportions, was used as early as the third millennium BC in the Aegean, Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia, and the second millennium BC in West India, Uzbekistan, Iran, Syria, Iraq, and Israel/Palestine.[3][4][5] Zinc metal was not produced on a large scale until the 12th century in India, though it was known to the ancient Romans and Greeks.[6] The mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC.[7] To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc.[8] Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow".

The element was probably named by the alchemist Paracelsus after the German word Zinke (prong, tooth). German chemist Andreas Sigismund Marggraf is credited with discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of iron (hot-dip galvanizing) is the major application for zinc. Other applications are in electrical batteries, small non-structural castings, and alloys such as brass. A variety of zinc compounds are commonly used, such as zinc carbonate and zinc gluconate (as dietary supplements), zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and dimethylzinc or diethylzinc in the organic laboratory.

Zinc is an essential mineral, including to prenatal and postnatal development.[9] Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.[10] In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea.[9] Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans.[11]

Consumption of excess zinc may cause ataxia, lethargy, and copper deficiency.

Characteristics

Physical properties

Zinc is a bluish-white, lustrous, diamagnetic metal,[12] though most common commercial grades of the metal have a dull finish.[13] 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.[14] The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.[12][13] Above 210 °C, the metal becomes brittle again and can be pulverized by beating.[15] Zinc is a fair conductor of electricity.[12] For a metal, zinc has relatively low melting (419.5 °C) and boiling points (907 °C).[16] The melting point is the lowest of all the d-block metals aside from mercury and cadmium; for this, among other reasons, zinc, cadmium, and mercury are often not considered to be transition metals like the rest of the d-block metals.[16]

Many alloys contain zinc, including 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.[17] Although neither zinc nor zirconium is ferromagnetic, their alloy ZrZn
2
exhibits ferromagnetism below 35 K.[12]

A bar of zinc generates a characteristic sound when bent, similar to tin cry.

Occurrence

Zinc makes up about 75 ppm (0.0075%) of Earth's crust, making it the 24th most abundant element. Soil contains zinc in 5–770 ppm with an average 64 ppm. Seawater has only 30 ppb and the atmosphere, 0.1–4 µg/m3.[18] The element is normally found in association with other base metals such as copper and lead in ores.[19] Zinc is a chalcophile, meaning the element is more likely to be found in minerals together 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 reducing conditions of the early Earth's atmosphere.[20] Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.[19]

Other source minerals for zinc include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate).[21] With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.[20]

Identified world zinc resources total about 1.9–2.8 billion tonnes.[22][23] Large deposits are in Australia, Canada and the United States, with the largest reserves in Iran.[20][24][25] The most recent estimate of reserve base for zinc (meets specified minimum physical criteria related to current mining and production practices) was made in 2009 and calculated to be roughly 480 Mt.[26] Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based (location, grade, quality, and quantity) at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by simply extrapolating the combined mine life of today's zinc mines. This concept is well supported by data from the United States Geological Survey (USGS), which illustrates that although refined zinc production increased 80% between 1990 and 2010, the reserve lifetime for zinc has remained unchanged. About 346 million tonnes have been extracted throughout history to 2002, and scholars have estimated that about 109–305 million tonnes are in use.[27][28][29]

A black shiny lump of solid with uneven surface

Isotopes

Five stable isotopes of zinc occur in nature, with 64Zn being the most abundant isotope (49.17% natural abundance).[30][31] The other isotopes found in nature are 66
Zn
(27.73%), 67
Zn
(4.04%), 68
Zn
(18.45%), and 70
Zn
(0.61%).[31] The most abundant isotope 64Zn and the rare 70Zn are theoretically unstable on energetic grounds, though their predicted half-lives exceed 4.3×1018 years[32] and 1.3×1016 years,[31] meaning that their radioactivity could be ignored for practical purposes.

Several dozen radioisotopes have been characterized. 65
Zn
, which has a half-life of 243.66 days, is the least active radioisotope, followed by 72
Zn
with a half-life of 46.5 hours.[30] Zinc has 10 nuclear isomers. 69mZn has the longest half-life, 13.76 h.[30] The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting a photon in the form of a gamma ray. 61
Zn
has three excited metastable states and 73
Zn
has two.[33] The isotopes 65
Zn
, 71
Zn
, 77
Zn
and 78
Zn
each have only one excited metastable state.[30]

The most common decay mode of a radioisotope of zinc with a mass number lower than 66 is electron capture. The decay product resulting from electron capture is an isotope of copper.[30]

n
30
Zn
+
e
n
29
Cu

The most common decay mode of a radioisotope of zinc with mass number higher than 66 is beta decay), which produces an isotope of gallium.[30]

n
30
Zn
n
31
Ga
+
e
+
ν
e

Compounds and chemistry

Reactivity

Zinc has an electron configuration of [Ar]3d104s2 and is a member of the group 12 of the periodic table. It is a moderately reactive metal and strong reducing agent.[34] The surface of the pure metal tarnishes quickly, eventually forming a protective passivating layer of the basic zinc carbonate, Zn
5
(OH)
6
(CO3)
2
, by reaction with atmospheric carbon dioxide.[35]

Zinc burns in air with a bright bluish-green flame, giving off fumes of zinc oxide.[36] Zinc reacts readily with acids, alkalis and other non-metals.[37] Extremely pure zinc reacts only slowly at room temperature with acids.[36] Strong acids, such as hydrochloric or sulfuric acid, can remove the passivating layer and subsequent reaction with water releases hydrogen gas.[36]

The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed, the outer shell s electrons are lost, yielding a bare zinc ion with the electronic configuration [Ar]3d10.[38] In aqueous solution an octahedral complex, [Zn(H
2
O)6]2+
is the predominant species.[39] The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of Zn
2
Cl
2
, a zinc compound with a +1 oxidation state.[36] No compounds of zinc in oxidation states other than +1 or +2 are known.[40] Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.[41]

Zinc chemistry is similar to the chemistry of the late first-row transition metals, nickel and copper, though it has a filled d-shell and compounds are diamagnetic and mostly colorless.[42] The ionic radii of zinc and magnesium happen to be nearly identical. Because of this some of the equivalent salts have the same crystal structure,[43] and in other circumstances where ionic radius is a determining factor, the chemistry of zinc has much in common with that of magnesium.[36] In other respects, there is little similarity with the late first-row transition metals. Zinc tends to form bonds with a greater degree of covalency and much more stable complexes with N- and S- donors.[42] Complexes of zinc are mostly 4- or 6- coordinate although 5-coordinate complexes are known.<

Brass, an alloy of copper and zinc in various proportions, was used as early as the third millennium BC in the Aegean, Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia, and the second millennium BC in West India, Uzbekistan, Iran, Syria, Iraq, and Israel/Palestine.[3][4][5] Zinc metal was not produced on a large scale until the 12th century in India, though it was known to the ancient Romans and Greeks.[6] The mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC.[7] To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc.[8] Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow".

The element was probably named by the alchemist Paracelsus after the German word Zinke (prong, tooth). German chemist Andreas Sigismund Marggraf is credited with discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of iron (hot-dip galvanizing) is the major application for zinc. Other applications are in electrical batteries, small non-structural castings, and alloys such as brass. A variety of zinc compounds are commonly used, such as zinc carbonate and zinc gluconate (as dietary supplements), zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and dimethylzinc or diethylzinc in the organic laboratory.

Zinc is an essential mineral, including to prenatal and postnatal development.[9] Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.[10] In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea.[9] Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans.[11]

Consumption of excess zinc may cause ataxia, lethargy, and copper deficiency.

Zinc is a bluish-white, lustrous, diamagnetic metal,[12] though most common commercial grades of the metal have a dull finish.[13] 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.[14] The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.[12][13] Above 210 °C, the metal becomes brittle again and can be pulverized by beating.[15] Zinc is a fair conductor of electricity.[12] For a metal, zinc has relatively low melting (419.5 °C) and boiling points (907 °C).[16] The melting point is the lowest of all the d-block metals aside from mercury and cadmium; for this, among other reasons, zinc, cadmium, and mercury are often not considered to be transition metals like the rest of the d-block metals.[16]

Many alloys contain zinc, including 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.[17] Although neither zinc nor zirconium is ferromagnetic, their alloy ZrZn
2
exhibits ferromagnetism below 35 K.[12]

A bar of zinc generates a characteristic sound when bent, similar to tin cry.

Occurrence

Zinc makes up about 75 ppm (0.0075%) of Earth's crust, making it the 24th most abundant element. Soil contains zinc in 5–770 ppm with an average 64 ppm. Seawater has only 30 ppb and the atmosphere, 0.1–4 µg/m3.[18] The element is normally found in association with other base metals such as copper and lead in ores.[19] Zinc is a chalcophile, meaning the element is more likely to be found in minerals together 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 reducing conditions of the early Earth's atmosphere.[20] Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.[19]

Other source minerals for zinc include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate).[21] With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.[20]

Identified world zinc resources total about 1.9–2.8 billion tonnes.[22][23] Large deposits are in Australia, Canada and the United States, with the largest reserves in Iran.[20][24][25] The most recent estimate of reserve base for zinc (meets specified minimum physical criteria related to current mining and production practices) was made in 2009 and calculated to be roughly 480 Mt.[26] Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based (location, grade, quality, and quantity) at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by simply extrapolating the combined mine life of today's zinc mines. This concept is well supported by data from the United States Geological Survey (USGS), which illustrates that although refined zinc production increased 80% between 1990 and 2010, the reserve lifetime for zinc has remained unchanged. About 346 million tonnes have been extracted throughout history to 2002, and scholars have estimated that about 109–305 million tonnes are in use.[27][28][29]

A black shiny lump of solid with uneven surfacealloys contain zinc, including 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.[17] Although neither zinc nor zirconium is ferromagnetic, their alloy ZrZn
2
exhibits ferromagnetism below 35 K.[12]

A bar of zinc generates a characteristic sound when bent, similar to tin cry.

Zinc makes up about 75 ppm (0.0075%) of Earth's crust, making it the 24th most abundant element. Soil contains zinc in 5–770 ppm with an average 64 ppm. Seawater has only 30 ppb and the atmosphere, 0.1–4 µg/m3.[18] The element is normally found in association with other base metals such as copper and lead in ores.[19] Zinc is a chalcophile, meaning the element is more likely to be found in minerals together 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 reducing conditions of the early Earth's atmosphere.[20] Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.[19]

Other source minerals for zinc include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (b

Other source minerals for zinc include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate).[21] With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.[20]

Identified world zinc resources total about 1.9–2.8 billion tonnes.[22][23] Large deposits are in Australia, Canada and the United States, with the largest reserves in Iran.[20][24][25] The most recent estimate of reserve base for zinc (meets specified minimum physical criteria related to current mining and production practices) was made in 2009 and calculated to be roughly 480 Mt.[26] Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based (location, grade, quality, and quantity) at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by simply extrapolating the combined mine life of today's zinc mines. This concept is well supported by data from the United States Geological Survey (USGS), which illustrates that although refined zinc production increased 80% between 1990 and 2010, the reserve lifetime for zinc has remained unchanged. About 346 million tonnes have been extracted throughout history to 2002, and scholars have estimated that about 109–305 million tonnes are in use.[27][28][29]

Five stable isotopes of zinc occur in nature, with 64Zn being the most abundant isotope (49.17% natural abundance).[30][31] The other isotopes found in nature are 66
Zn
(27.73%), 67
Zn
(4.04%), 68
Zn
(18.45%), and 70
Zn
(0.61%).[31] The most abundant isotope 64Zn and the rare 70Zn are theoretically unstable on energetic grounds, though their predicted half-lives exceed 4.3×1018 years[32] and 1.3×1016 years,[31] meaning that their radioactivity could be ignored for practical purposes.

Several dozen radioisotopes have been characterized. 65
Zn
, which has a half-life of 243.66 days, is the least active radioisotope, followed by 72
Zn
with a half-life of 46.5 hours.[30] Zinc has 10 nuclear isomers. 69mZn has the longest half-life, 13.76 h.radioisotopes have been characterized. 65
Zn
, which has a half-life of 243.66 days, is the least active radioisotope, followed by 72
Zn
with a half-life of 46.5 hours.[30] Zinc has 10 nuclear isomers. 69mZn has the longest half-life, 13.76 h.[30] The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting a photon in the form of a gamma ray. 61
Zn
has three excited metastable states and 73
Zn
has two.[33] The isotopes 65
Zn
, 71
Zn
, 77
Zn
and 78
Zn
each have only one excited metastable state.[30]

The most common decay mode of a radioisotope of zinc with a mass number lower than 66 is electron capture. The decay product resulting from electron capture is an isotope of copper.[30]

The most common decay mode of a radioisotope of zinc with mass number higher than 66 is beta decay), which produces an isotope of gallium.[30]

n
30
Zn
n
31
Ga
+
e
+ Zinc has an electron configuration of [Ar]3d104s2 and is a member of the group 12 of the periodic table. It is a moderately reactive metal and strong reducing agent.[34] The surface of the pure metal tarnishes quickly, eventually forming a protective passivating layer of the basic zinc carbonate, Zn
5
(OH)
6
(CO3)
2
, by reaction with atmospheric carbon dioxide.[35]

Zinc burns in air with a bright bluish-green flame, giving off fumes of zinc oxide.[36] Zinc reacts readily with acids, alkalis and other non-metals.[37] Extremely pure zinc reacts only slowly at room temperature with acids.[36] Strong acids, such as hydrochloric or sulfuric acid, can remove the passivating layer and subsequent reaction with water releases hydrogen gas.[36]

The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed, the outer shell s electrons are lost, yielding a bare zinc ion with the electronic configuration [Ar]3d10.[38] In aqueous solution an octahedral complex, [Zn(H
2
O)6]2+
is the predominant species.[39] The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of Zn
2
Cl
2
, a zinc compound with a +1 oxidation state.[36] No compounds of zinc in oxidation states other than +1 or +2 are known.[40] Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.[41]

Zinc chemistry is similar to the chemistry of the late first-row transition metals, nickel and copper, though it has a filled d-shell and compounds ar

Zinc burns in air with a bright bluish-green flame, giving off fumes of zinc oxide.[36] Zinc reacts readily with acids, alkalis and other non-metals.[37] Extremely pure zinc reacts only slowly at room temperature with acids.[36] Strong acids, such as hydrochloric or sulfuric acid, can remove the passivating layer and subsequent reaction with water releases hydrogen gas.[36]

The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed, the outer shell s electrons are lost, yielding a bare zinc ion with the electronic configuration [Ar]3d10.[38] In aqueous solution an octahedral complex, [Zn(H
2
O)6]2+
is the predominant species.[39] The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of Zn
2
Cl
2
, a zinc compound with a +1 oxidation state.[36] No compounds of zinc in oxidation states other than +1 or +2 are known.[40] Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.[41]

Zinc chemistry is similar to the chemistry of the late first-row transition metals, nickel and copper, though it has a filled d-shell and compounds are diamagnetic and mostly colorless.[42] The ionic radii of zinc and magnesium happen to be nearly identical. Because of this some of the equivalent salts have the same crystal structure,[43] and in other circumstances where ionic radius is a determining factor, the chemistry of zinc has much in common with that of magnesium.[36] In other respects, there is little similarity with the late first-row transition metals. Zinc tends to form bonds with a greater degree of covalency and much more stable complexes with N- and S- donors.[42] Complexes of zinc are mostly 4- or 6- coordinate although 5-coordinate complexes are known.[36]

Zinc(I) compounds are rare and need bulky ligands to stabilize the low oxidation state. Most zinc(I) compounds contain formally the [Zn2]2+ core, which is analogous to the [Hg2]2+ dimeric cation present in mercury(I) compounds. The diamagnetic nature of the ion confirms its dimeric structure. The first zinc(I) compound containing the Zn–Zn bond, 5-C5Me5)2Zn2, is also the first dimetallocene. The [Zn2]2+ ion rapidly disproportionates into zinc metal and zinc(II), and has been obtained only a yellow glass only by cooling a solution of metallic zinc in molten ZnCl2.[44]

Zinc(II) compoundsBinary compounds of zinc are known for most of the metalloids and all the nonmetals except the noble gases. The oxide ZnO is a white powder that is nearly insoluble in neutral aqueous solutions, but is amphoteric, dissolving in both strong basic and acidic solutions.[36] The other chalcogenides (ZnS, ZnSe, and ZnTe) have varied applications in electronics and optics.[45] Pnictogenides (Zn
3
N
2
, Zn
3
P
2
, Zn
3
As
2
and Zn
3
Sb
2
),[46][47] the peroxide (ZnO
2
), the hydride (ZnH
2
), and the carbide (ZnC
2
) are also known.[48] Of the four halides, ZnF
2
has the most ionic character, while the others (ZnCl
2
, ZnBr
2
, and ZnI
2
) have relatively low melting points and are considered to have more covalent character.[49]

In weak basic solutions containing Zn2+
ions, the hydroxide Zn(OH)
2
forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([Zn(OH)4]2−
).[36] The nitrate Zn(NO3)
2

In weak basic solutions containing Zn2+
ions, the hydroxide
Zn(OH)
2
forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([Zn(OH)4]2−
).[36] The nitrate Zn(NO3)
2
, chlorate Zn(ClO3)
2
, sulfate ZnSO
4
, phosphate Zn
3
(PO4)
2
, molybdate ZnMoO
4
, cyanide Zn(CN)
2
, arsenite Zn(AsO2)
2
, arsenate Zn(AsO4)
2
·8H
2
O
and the chromate ZnCrO
4
(one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc.[50][51] One of the simplest examples of an organic compound of zinc is the acetate (Zn(O
2
CCH3)
2
).

Organozinc compounds are those that contain zinc–carbon covalent bonds. Diethylzinc ((C
2
H5)
2
Zn
) is a reagent in synthetic chemistry. It was first reported in 1848 from the reaction of zinc and ethyl iodide, and was the first compound known to contain a metal–carbon sigma bond.[52]

Cobalticyanide paper (Rinnmann's test for Zn) can be used as a chemical indicator for zinc. 4 g of K3Co(CN)6 and 1 g of KClO3 is dissolved on 100 ml of water. Paper is dipped in the solution and dried at 100 °C. One drop of the sample is dropped onto the dry paper and heated. A green disc indicates the presence of zinc.[53]

History

Refinement of sulfidic zinc ores produces large volumes of sulfur dioxide and cadmium vapor. Smelter slag and other residues contain significant quantities of metals. About 1.1 million tonnes of metallic zinc and 130 thousand tonnes of lead were mined and smelted in the Belgian towns of La Calamine and Plombières between 1806 and 1882.[98] The dumps of the past mining operations leach zinc and cadmium, and the sediments of the Geul River contain non-trivial amounts of metals.[98] About two thousand years ago, emiss

When galvanised feedstock is fed to an electric arc furnace, the zinc is recovered from the dust by a number of processes, predominantly the Waelz process (90% as of 2014).[97]

Refinement of sulfidic zinc ores produces large volumes of sulfur dioxide and cadmium vapor. Smelter slag and other residues contain significant quantities of metals. About 1.1 million tonnes of metallic zinc and 130 thousand tonnes of lead were mined and smelted in the Belgian towns of La Calamine and Plombières between 1806 and 1882.[98] The dumps of the past mining operations leach zinc and cadmium, and the sediments of the Geul River contain non-trivial amounts of metals.[98] About two thousand years ago, emissions of zinc from mining and smelting totaled 10 thousand tonnes a year. After increasing 10-fold from 1850, zinc emissions peaked at 3.4 million tonnes per year in the 1980s and declined to 2.7 million tonnes in the 1990s, although a 2005 study of the Arctic troposphere found that the concentrations there did not reflect the decline. Man-made and natural emissions occur at a ratio of 20 to 1.[99]

Zinc in rivers flowing through industrial and mining areas can be as high as 20 ppm.[100] Effective sewage treatment greatly reduces this; treatme

Zinc in rivers flowing through industrial and mining areas can be as high as 20 ppm.[100] Effective sewage treatment greatly reduces this; treatment along the Rhine, for example, has decreased zinc levels to 50 ppb.[100] Concentrations of zinc as low as 2 ppm adversely affects the amount of oxygen that fish can carry in their blood.[101]

Soils contaminated with zinc from mining, refining, or fertilizing with zinc-bearing sludge can contain several grams of zinc per kilogram of dry soil. Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other essential metals, such as iron and manganese. Zinc levels of 2000 ppm to 180,000 ppm (18%) have been recorded in some soil samples.[100]

Applications

Major applications of zinc include (numbers are given for the US)[104]

  1. Galvanizing (55%)
  2. Brass and bronze (16%)
  3. Other alloys (21%)
  4. Miscellaneous (8%)

Anti-corrosion and batteries

Merged elongated crystals of various shades of gray.
[104]

  1. Galvanizing (55%)
  2. Brass and bronze (16%)
  3. Other alloys (21%)
  4. Miscellaneous (8%)

corrosion agent,[105] and galvanization (coating of iron or steel) is the most familiar form. In 2009 in the United States, 55% or 893,000 tons of the zinc metal was used for galvanization.[104]

Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.[106] A protective surface layer of oxide and carbonate (Zn
5
(OH)
6
(CO
3
)
2
)
forms as the zinc corrodes.Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.[106] A protective surface layer of oxide and carbonate (Zn
5
(OH)
6
(CO
3
)
2
)
forms as the zinc corrodes.[107] This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away.[107] The zinc is applied electrochemically or as molten zinc by hot-dip galvanizing or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, lightposts, metal roofs, heat exchangers, and car bodies.[18]

The relative reactivity of zinc and its ability to attract oxidation to itself makes it an efficient sacrificial anode in cathodic protection (CP). For example, cathodic protection of a buried pipeline can be achieved by connecting anodes made from zinc to the pipe.[107] Zinc acts as the anode (negative terminus) by slowly corroding away as it passes electric current to the steel pipeline.[107][note 2] Zinc is also used to cathodically protect metals that are exposed to sea water.[108] A zinc disc attached to a ship's iron rudder will slowly corrode while the rudder stays intact.[106] Similarly, a zinc plug attached to a propeller or the metal protective guard for the keel of the ship provides temporary protection.

With a standard electrode potential (SEP) of −0.76 volts, zinc is used as an anode material for batteries. (More reactive lithium (SEP −3.04 V) is used for anodes in lithium batteries ). Powdered zinc is used in this way in alkaline batteries and the case (which also serves as the anode) of zinc–carbon batteries is formed from sheet zinc.[109][110] Zinc is used as the anode or fuel of the zinc-air battery/fuel cell.[111][112][113] The zinc-cerium redox flow battery also relies on a zinc-based negative half-cell.[114]

A widely used zinc alloy is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass.[107] Brass is generally more ductile and stronger than copper, and has superior corrosion resistance.[107] These properties make it useful in communication equipment, hardware, musical instruments, and water valves.[107]

A mosaica pattern composed of components having various shapes and shades of brown.nickel silver, typewriter metal, soft and aluminium solder, and commercial bronze.[12] Zinc is also used in contemporary pipe organs as a substitute for the traditional lead/tin alloy in pipes.[115] Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Zinc is the primary metal in American one cent coins (pennies) since 1982.[116] The zinc core is coated with a thin layer of copper to give the appearance of a copper coin. In 1994, 33,200 tonnes (36,600 short tons) of zinc were used to produce 13.6 billion pennies in the United States.[117]

Alloys of zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting, especially in the automotive, electrical, and hardware industries.[12] These alloys are marketed under the name Zamak.[118] An example of this is zinc aluminium. The low melting point together with the low viscosity of the alloy makes possible the production of small and intricate shapes. The low working temperature leads to rapid cooling of the cast products and fast production for assembly.[12][119] Another alloy, marketed under the brand name Prestal, contains 78% zinc and 22% aluminium, and

Alloys of zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting, especially in the automotive, electrical, and hardware industries.[12] These alloys are marketed under the name Zamak.[118] An example of this is zinc aluminium. The low melting point together with the low viscosity of the alloy makes possible the production of small and intricate shapes. The low working temperature leads to rapid cooling of the cast products and fast production for assembly.[12][119] Another alloy, marketed under the brand name Prestal, contains 78% zinc and 22% aluminium, and is reported to be nearly as strong as steel but as malleable as plastic.[12][120] This superplasticity of the alloy allows it to be molded using die casts made of ceramics and cement.[12]

Similar alloys with the addition of a small amount of lead can be cold-rolled into sheets. An alloy of 96% zinc and 4% aluminium is used to make stamping dies for low production run applications for which ferrous metal dies would be too expensive.[121] For building facades, roofing, and other applications for sheet metal formed by deep drawing, roll forming, or bending, zinc alloys with titanium and copper are used.[122] Unalloyed zinc is too brittle for these manufacturing processes.[122]

As a dense, inexpensive, easily worked material, zinc is used as a lead replacement. In the wake of lead concerns, zinc appears in weights for various applications ranging from fishing[123] to tire balances and flywheels.[124]

Cadmium zinc telluride (CZT) is a semiconductive alloy that can be divided into an array of small sensing devices.[125] These devices are similar to an integrated circuit and can detect the energy of incoming gamma ray photons.[125] When behind an absorbing mask, the CZT sensor array can determine the direction of the rays.[125]

Roughly one quarter of all zinc output in the United States in 2009 was consumed in zinc compounds;[104] a variety of which are used industrially. Zinc oxide is widely used as a white pigment in paints and as a catalyst in the manufacture of rubber to disperse heat. Zinc oxide is used to protect rubber polymers and plastics from ultraviolet radiation (UV).[18] The semiconductor properties of zinc oxide make it useful in varistors and photocopying products.[126] The zinc zinc-oxide cycle is a two step thermochemical process based on zinc and zinc oxide for hydrogen production.[127]

Zinc chloride is often added to lumber as a fire retardant[128] and sometimes as a wood preservative.[129] It is used in the manufacture of other chemicals.[128] Zinc methyl (Zn(CH3)
2
) is used in a number of organic Zinc chloride is often added to lumber as a fire retardant[128] and sometimes as a wood preservative.[129] It is used in the manufacture of other chemicals.[128] Zinc methyl (Zn(CH3)
2
) is used in a number of organic syntheses.[130] Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints.[131] Crystals of ZnS are used in lasers that operate in the mid-infrared part of the spectrum.[132] Zinc sulfate is a chemical in dyes and pigments.[128] Zinc pyrithione is used in antifouling paints.[133]

Zinc powder is sometimes used as a propellant in model rockets.[134] When a compressed mixture of 70% zinc and 30% sulfur powder is ignited there is a violent chemical reaction.[134] This produces zinc sulfide, together with large amounts of hot gas, heat, and light.[134]

Zinc sheet metal is used to make zinc bars.[135]

64
Zn
, the most abundant isotope of zinc, is very susceptible to neutron activation, being transmuted into the highly radioactive 65
Zn
, which has a half-life of 244 days and produces intense gamma radiation. Because of this, zinc oxide used in nuclear reactors as an anti-corrosion agent is depleted of 64
Zn
before use, this is called depleted zinc oxide. For the same reason, zinc has been proposed as a salting material for nuclear weapons (cobalt is another, better-known salting material).[136] A jacket of isotopically enriched 64
Zn
would be irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, forming a large amount of 65
Zn
significantly increasing the radioactivity of the weapon's fallout.[136] Such a weapon is not known to have ever been built, tested, or used.[136]

65
Zn
is used as a tracer to study how alloys that contain zinc wear out, or the path and the role of zinc in organisms.[137]

Zinc dithiocarbamate complexes are used as agricultural fungicides; these include Zineb, Metiram, Propineb and Ziram.[138] Zinc naphthenate is used as wood preservative.[139] Zinc in the form of ZDDP, is used as an anti-wear additive for metal parts in engine oil.[140]

Organozinc chemistry is the science of compounds that contain carbon-zinc bonds, describing the physical properties, synthesis, and chemical reactions. Many organozinc compounds are important.[141][142][143][144] Among important applications are

  • The Frankland-Duppa Reaction in which an oxalate ester (ROCOCOOR) reacts with an alkyl halide R'X, zinc and hydrochloric acid to form the α-hydroxycarboxylic esters RR'COHCOOR[145][146]
  • The Reformatskii reaction in which α-halo-esters and aldehydes are converted to β-hydroxy-esters
  • The Simmons–Smith reaction in which the carbenoid (iodomethyl)zinc iodide reacts with alkene(or alkyne) and converts them to cyclopropane
  • The Addition reaction of organozinc compounds to form enantiomeric excess) obtained with chiral zinc catalysts are comparable to those achieved with palladium, ruthenium, iridium and others, and zinc becomes a metal catalyst of choice.[149]

    Dietary supplement

    GNC zinc 50 mg tablets. The amount exceeds what is deemed the safe upper limit in the United States (40 mg) and European Union (25 mg)
    Skeletal chemical formula of a planar compound featuring a Zn atom in the center, symmetrically bonded to four oxygens. Those oxygens are further connected to linear COH chains.
    Zinc gluconate is one compound used for the delivery of zinc as a dietary supplement.

    In most single-tablet, over-the-counter, daily vitamin and mineral supplements, zinc is included in such forms as zinc oxide, zinc acetate, or In most single-tablet, over-the-counter, daily vitamin and mineral supplements, zinc is included in such forms as zinc oxide, zinc acetate, or zinc gluconate.[150] Generally, zinc supplement is recommended where there is high risk of zinc deficiency (such as low and middle income countries) as a preventive measure.[151] Although zinc sulfate is a commonly used zinc form, zinc citrate, gluconate and picolinate may be valid options as well. These forms are better absorbed than zinc oxide.[152]

    Gastroenteritis

    Zinc is an inexpensive and effective part of treatment of diarrhea among children in the developing world. Zinc becomes depleted in the body during diarrhea and replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for as long as three months.[153] Gastroenteritis is strongly attenuated by ingestion of zinc, possibly by direct antimicrobial action of the ions in the gastrointestinal tract, or by the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both.[154][155]

    Common cold

    Zinc supplements (frequently zinc acetate or Zinc is an inexpensive and effective part of treatment of diarrhea among children in the developing world. Zinc becomes depleted in the body during diarrhea and replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for as long as three months.[153] Gastroenteritis is strongly attenuated by ingestion of zinc, possibly by direct antimicrobial action of the ions in the gastrointestinal tract, or by the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both.[154][155]

    Common cold

    A Cochrane review stated that people taking zinc supplement may be less likely to progress to age-related macular degeneration.[162] Zinc supplement is an effective treatment for acrodermatitis enteropathica, a genetic disorder affecting zinc absorption that was previously fatal to affected infants.[57] Zinc deficiency has been associated with major depressive disorder (MDD), and zinc supplements may be an effective treatment.[163]

    Topical use

    A Cochrane review stated that people taking zinc supplement may be less likely to progress to age-related macular degeneration.[162] Zinc supplement is an effective treatment for acrodermatitis enteropathica, a genetic disorder affecting zinc absorption that was previously fatal to affected infants.[57] Zinc deficiency has been associated with major depressive disorder (MDD), and zinc supplements may be an effective treatment.[163]

    Topical use<

    Zinc serves a purely structural role in zinc fingers, twists and clusters.[194] Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA base sequences during the replication and transcription of DNA. Each of the nine or ten Zn2+
    ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.[190] The transcription factor wraps around the DNA helix and uses its fingers to accurately bind to the DNA sequence.

    In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%).In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%).[176] Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper.[195] The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake.[186] Cells in the salivary gland, prostate, immune system, and intestine use zinc signaling to communicate with other cells.[196]

    Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals.[197] Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%.[198] However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.[199]

    The human dopamine transporter contains a high affinity extracellular zinc binding site which, upon zinc binding, inhibits dopamine reuptake and amplifies amphetamine-induced dopamine efflux in vitro.[200][201][202] The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites.[202] Some EF-hand calcium binding proteins such as S100 or NCS-1 are also able to bind zinc ions.[203]

    The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for zinc in 2001. The current EARs for zinc for women and men ages 14 and up is 6.8 and 9.4 mg/day, respectively. The RDAs are 8 and 11 mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 11 mg/day. RDA for lactation is 12 mg/day. For infants up to 12 months the RDA is 3 mg/day. For children ages 1–13 years the RDA increases with age from 3 to 8 mg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of zinc the adult UL is 40 mg/day (lower for children). Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).[186]

    The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For people ages 18 and older the PRI calculations are complex, as the EFSA has set higher and higher values as the phytate content of the diet increases. For women, PRIs increase from 7.5 to 12.7 mg/day as phyta