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______ is a chemical element; it has symbol 1__ (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.
In the Roman era, copper was mined principally on Cyprus, the origin of the name of the metal, from 2___________ (metal of Cyprus), later corrupted to cuprum (Latin). 3_____ (Old English) and 4______ were derived from this, the later spelling first used around 1530.[7]
Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.
Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found mainly in the liver, muscle, and bone.[8] The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight.[9]
Copper, silver, and gold are in group 11 of the periodic table; these three metals have one s-orbital electron on top of a filled d-electron shell and are characterized by high ductility, and electrical and thermal conductivity. The filled d-shells in these elements contribute little to interatomic interactions, which are dominated by the s-electrons through metallic bonds. Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper.[10] At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is usually supplied in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms.[11]
The softness of copper partly explains its high electrical conductivity (59.6106 S/m) and high thermal conductivity, second highest (second only to silver) among pure metals at room temperature.[12] This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal.[10] The maximum permissible[5_________] current density of copper in open air is approximately 3.1106 A/m2, above which it begins to heat excessively.[13]
Copper is one of a few metallic elements with a natural color other than gray or silver.[14] Pure copper is orange-red and acquires a reddish tarnish when exposed to air. This is due to the low plasma frequency of the metal, which lies in the red part of the visible spectrum, causing it to absorb the higher-frequency green and blue colors.[15]
Copper does not react with water, but it does slowly react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms on iron in moist air, protects the underlying metal from further corrosion (passivation). A green layer of verdigris (copper carbonate) can often be seen on old copper structures, such as the roofing of many older buildings[17] and the Statue of Liberty.[18] Copper tarnishes when exposed to some sulfur compounds, with which it reacts to form various copper sulfides.[19]
Copper is produced in massive stars[23] and is present in the Earth's crust in a proportion of about 50 parts per million (ppm).[24] In nature, copper occurs in a variety of minerals, including native copper, copper sulfides such as chalcopyrite, bornite, digenite, covellite, and chalcocite, copper sulfosalts such as tetrahedite-tennantite, and enargite, copper carbonates such as azurite and malachite, and as copper(I) or copper(II) oxides such as cuprite and tenorite, respectively.[12] The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US.[24] Native copper is a polycrystal, with the largest single crystal ever described measuring 4.4 3.2 3.2 cm.[25] Copper is the 25th most abundant element in Earth's crust, representing 50 ppm compared with 75 ppm for zinc, and 14 ppm for lead.[26]
Copper has been in use for at least 10,000 years, but more than 95% of all copper ever mined and smelted has been extracted since 1900.[31] As with many natural resources, the total amount of copper on Earth is vast, with around 1014 tons in the top kilometer of Earth's crust, which is about 5 million years' worth at the current rate of extraction. However, only a tiny fraction of these reserves is economically viable with present-day prices and technologies. Estimates of copper reserves available for mining vary from 25 to 60 years, depending on core assumptions such as the growth rate.[32] Recycling is a major source of copper in the modern world.[31]
The great majority of copper ores are sulfides. Common ores are the sulfides chalcopyrite (CuFeS2), bornite (Cu5FeS4) and, to a lesser extent, covellite (CuS) and chalcocite (Cu2S).[35] These ores occur at the level of
This roasting gives matte copper, roughly 50% Cu by weight, which is purified by electrolysis. Depending on the ore, sometimes other metals are obtained during the electrolysis including platinum and gold.
Aside from sulfides, another family of ores are oxides. Approximately 15% of the world's copper supply derives from these oxides. The beneficiation process for oxides involves extracton with sulfuric acid solutions followed by electrolysis. In parallel with the above method for "concentrated" sulfide and oxide ores, copper is recovered from mine tailings and heaps. A variety of methods are used including leaching with sulfuric acid, ammonia, ferric chloride. Biological methods are also used.[36] [37]
A significant source of copper is from recycling. Recycling is facilitated because copper is usually deployed in its metallic state. In 2001, a typical automobile contained 20-30 kg of copper. Recycling usually begins with some melting process using a blast furnace.[36]
The process of recycling copper is roughly the same as is used to extract copper but requires fewer steps. High-purity scrap copper is melted in a furnace and then reduced and cast into billets and ingots; lower-purity scrap is refined by electroplating in a bath of sulfuric acid.[43]
The environmental cost of copper mining was estimated at 3.7 kg CO2eq per kg of copper in 2019.[44] Codelco, a major producer in Chile, reported that in 2020 the company emitted 2.8t CO2eq per ton (2.8 kg CO2eq per kg) of fine copper.[45] Greenhouse gas emissions primarily arise from electricity consumed by the company, especially when sourced from fossil fuels, and from engines required for copper extraction and refinement. Companies that mine land often mismanage waste, rendering the area sterile for life. Additionally, nearby rivers and forests are also negatively impacted. The Philippines is an example of a region where land is overexploited by mining companies.[46]
Numerous copper alloys have been formulated, many with important uses. Brass is an alloy of copper and zinc. Bronze usually refers to copper-tin alloys, but can refer to any alloy of copper such as aluminium bronze. Copper is one of the most important constituents of silver and karat gold solders used in the jewelry industry, modifying the color, hardness and melting point of the resulting alloys.[50] Some lead-free solders consist of tin alloyed with a small proportion of copper and other metals.[51]
Cuprous halides with fluorine, chlorine, bromine, and iodine are known, as are cupric halides with fluorine, chlorine, and bromine. Attempts to prepare copper(II) iodide yield only copper(I) iodide and iodine.[56]
Many other oxyanions form complexes; these include copper(II) acetate, copper(II) nitrate, and copper(II) carbonate. Copper(II) sulfate forms a blue crystalline pentahydrate, the most familiar copper compound in the laboratory. It is used in a fungicide called the Bordeaux mixture.[60]
Polyols, compounds containing more than one alcohol functional group, generally interact with cupric salts. For example, copper salts are used to test for reducing sugars. Specifically, using Benedict's reagent and Fehling's solution the presence of the sugar is signaled by a color change from blue Cu(II) to reddish copper(I) oxide.[61] Schweizer's reagent and related complexes with ethylenediamine and other amines dissolve cellulose.[62] Amino acids such as cystine form very stable chelate complexes with copper(II)[63][64][65] including in the form of metal-organic biohybrids (MOBs). Many wet-chemical tests for copper ions exist, one involving potassium ferricyanide, which gives a brilliant blue precipitate with copper(II) salts.[66]
Copper(III) is most often found in oxides. A simple example is potassium cuprate, KCuO2, a blue-black solid.[73] The most extensively studied copper(III) compounds are the cuprate superconductors. Yttrium barium copper oxide (YBa2Cu3O7) consists of both Cu(II) and Cu(III) centres. Like oxide, fluoride is a highly basic anion[74] and is known to stabilize metal ions in high oxidation states. Both copper(III) and even copper(IV) fluorides are known, K3CuF6 and Cs2CuF6, respectively.[56]
tzi the Iceman, a male dated from 3300 to 3200 BC, was found with an axe with a copper head 99.7% pure; high levels of arsenic in his hair suggest an involvement in copper smelting.[88] Experience with copper has assisted the development of other metals; in particular, copper smelting led to the discovery of iron smelting.[88] 5376163bf9
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