Zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) 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.[b] 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).
This article is about the chemical element. For other uses, see Zinc (disambiguation).Zinc
silver-gray
$_$_$DEEZ_NUTS#1__answer--1DEEZ_NUTS$_$_$
30
[Ar] 3d10 4s2
2, 8, 18, 2
692.68 K (419.53 °C, 787.15 °F)
1180 K (907 °C, 1665 °F)
7.140 g/cm3 [3]
6.57 g/cm3
7.32 kJ/mol
115 kJ/mol
25.470 J/(mol·K)
−2, 0, +1, +2 (an amphoteric oxide)
Pauling scale: 1.65
- 1st: 906.4 kJ/mol
- 2nd: 1733.3 kJ/mol
- 3rd: 3833 kJ/mol
- (more)
empirical: 134 pm
122±4 pm
139 pm
hexagonal close-packed (hcp) (hP2)
30.08×10−6/K (at 20 °C)[a]
116 W/(m⋅K)
59.0 nΩ⋅m (at 20 °C)
−11.4×10−6 cm3/mol (298 K)[4]
108 GPa
43 GPa
70 GPa
3850 m/s (at r.t.) (rolled)
0.25
2.5
327–412 MPa
7440-66-6
Indian metallurgists (before 1000 BCE)
Andreas Sigismund Marggraf (1746)
Rasaratna Samuccaya (1300)
Zinc is an essential trace element for humans,[6][7][8] animals,[9] plants[10] and for microorganisms[11] and is necessary for prenatal and postnatal development.[12] It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all enzyme classes.[10][8] Zinc is also an essential nutrient element for coral growth as it is an important cofactor for many enzymes.[13]
Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.[14] In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea.[12] Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans.[15] Consumption of excess zinc may cause ataxia, lethargy, and copper deficiency. In marine biomes, notably within polar regions, a deficit of zinc can compromise the vitality of primary algal communities, potentially destabilizing the intricate marine trophic structures and consequently impacting biodiversity.[16]
Brass, an alloy of copper and zinc in various proportions, was used as early as the third millennium BC in the Aegean area and the region which currently includes Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia. In the second millennium BC it was used in the regions currently including West India, Uzbekistan, Iran, Syria, Iraq, and Israel.[17][18][19] 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.[20] The mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC.[21] 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.[22] 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.
Characteristics[edit]
Physical properties[edit]
Zinc is a bluish-white, lustrous, diamagnetic metal,[23] though most common commercial grades of the metal have a dull finish.[24] 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.[25] The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.[23][24] Above 210 °C, the metal becomes brittle again and can be pulverized by beating.[26] Zinc is a fair conductor of electricity.[23] For a metal, zinc has relatively low melting (419.5 °C) and boiling point (907 °C).[27] The 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.[27]
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.[28] Although neither zinc nor zirconium is ferromagnetic, their alloy, ZrZn
2, exhibits ferromagnetism below 35 K.[23]
History[edit]
Ancient use[edit]
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.[18]
Knowledge of how to produce brass spread to Ancient Greece by the 7th century BC, but few varieties were made.[19] 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.[32] A possibly prehistoric statuette containing 87.5% zinc was found in a Dacian archaeological site.[69]
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.[70] Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.[71]
The manufacture of brass was known to the Romans by about 30 BC.[72] They made brass by heating powdered calamine (zinc silicate or carbonate), charcoal and copper together in a crucible.[72] The resulting calamine brass was then either cast or hammered into shape for use in weaponry.[73] Some coins struck by Romans in the Christian era are made of what is probably calamine brass.[74]