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reddish/orange metallic lustre metallic copper | |||||||||||||||||||
Phase | solid | ||||||||||||||||||
Density (near r.t.) | 8.94 g·cm−3 | ||||||||||||||||||
Liquid density at m.p. | 8.02 g·cm−3 | ||||||||||||||||||
Melting point | 1357.77 K, 1084.62 °C, 1984.32 °F | ||||||||||||||||||
boiling point | 2835 K, 2562 °C, 4643 °F | ||||||||||||||||||
Heat of fusion | 13.26 kJ·mol−1 | ||||||||||||||||||
Heat of vaporization | 300.4 kJ·mol−1 | ||||||||||||||||||
Specific heat capacity | (25 °C) 24.440 J·mol−1·K−1 | ||||||||||||||||||
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Oxidation states | +1, +2, +3, +4 (mildly basic oxide) | ||||||||||||||||||
Electronegativity | 1.90 (Pauling scale) | ||||||||||||||||||
Ionization energies (more) | 1st: 745.5 kJ·mol−1 | ||||||||||||||||||
2nd: 1957.9 kJ·mol−1 | |||||||||||||||||||
3rd: 3555 kJ·mol−1 | |||||||||||||||||||
Atomic radius | 128 pm | ||||||||||||||||||
Covalent radius | 132±4 pm | ||||||||||||||||||
Van der Waals radius | 140 pm | ||||||||||||||||||
Crystal structure | face-centered cubic | ||||||||||||||||||
Magnetic ordering | diamagnetic | ||||||||||||||||||
Electrical resistivity | (20 °C) 16.78 nΩ·m | ||||||||||||||||||
Thermal conductivity | (300 K) 401 W·m−1·K−1 | ||||||||||||||||||
Thermal expansion | (25 °C) 16.5 µm·m−1·K−1 | ||||||||||||||||||
Speed of sound (thin rod) | (r.t.) (annealed) 3810 m·s−1 | ||||||||||||||||||
Young's modulus | 110–128 GPa | ||||||||||||||||||
Shear modulus | 48 GPa | ||||||||||||||||||
Bulk modulus | 140 GPa | ||||||||||||||||||
Poisson ratio | 0.34 | ||||||||||||||||||
Mohs hardness | 3.0 | ||||||||||||||||||
Vickers hardness | 369 MPa | ||||||||||||||||||
Brinell hardness | 874 MPa | ||||||||||||||||||
CAS registry number | 7440-50-8 | ||||||||||||||||||
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copper disc made by continuous casting, etched
Copper metal and alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus", later shortened to Cuprum. There may be insufficient reserves to sustain current high rates of copper consumption.[1] Some countries, such as Chile and the United States, still have sizable reserves of the metal which are extracted through large open pit mines.
Copper compounds are known in several oxidation states, usually 2+, where they often impart blue or green colors to natural minerals such as turquoise and have been used historically widely as pigments. Copper as both metal and pigmented salt, has a significant presence in decorative art. Copper 2+ ions are soluble in water, where they function at low concentration as bacteriostatic substances and fungicides. For this reason, copper metal can be used as an anti-germ surface that can add to the anti-bacterial and antimicrobial features of buildings such as hospitals.[2] In sufficient amounts, copper salts can be poisonous to higher organisms as well. However, despite universal toxicity at high concentrations, the 2+ copper ion at lower concentrations is an essential trace nutrient to all higher plant and animal life. In animals, including humans, it is found widely in tissues, with concentration in liver, muscle, and bone. It functions as a co-factor in various enzymes and in copper-based pigments.
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History
Copper Age
Main article: Copper Age
Copper, as native copper, is one of the few metals to occur naturally as an un-compounded mineral. Copper was known to some of the oldest civilizations on record, and has a history of use that is at least 10,000 years old. Some estimates of copper's discovery place this event around 9000 BC in the Middle East.[3] A copper pendant was found in what is now northern Iraq that dates to 8700 BC.[4] It is probable that gold and meteoritic iron were the only metals used by humans before copper.[5] By 5000 BC, there are signs of copper smelting: the refining of copper from simple copper compounds such as malachite or azurite. Among archaeological sites in Anatolia, Çatal Höyük (~6000 BC) features native copper artifacts and smelted lead beads, but no smelted copper. Can Hasan (~5000 BC) had access to smelted copper but the oldest smelted copper artifact found (a copper chisel from the chalcolithic site of Prokuplje in Serbia) has pre-dated Can Hasan by 500 years. The smelting facilities in the Balkans appear to be more advanced than the Turkish forges found at a later date, so it is quite probable that copper smelting originated in the Balkans. Investment casting was realized in 4500-4000 BCE in Southeast Asia.[3]Ancient Copper ingot from Zakros, Crete is shaped in the form of an animal skin typical for that era.
In the Americas production in the Old Copper Complex, located in present day Michigan and Wisconsin, was dated back to between 6000 to 3000 BC.[7]
Bronze Age
Alloying of copper with zinc or tin to make brass or bronze was practiced soon after the discovery of copper itself. There exist copper and bronze artifacts from Sumerian cities that date to 3000 BC,[8] and Egyptian artifacts of copper and copper-tin alloys nearly as old. In one pyramid, a copper plumbing system was found that is 5000 years old.[9] The Egyptians found that adding a small amount of tin made the metal easier to cast, so copper-tin (bronze) alloys were found in Egypt almost as soon as copper was found. Very important sources of copper in the Levant were located in Timna valley (Negev, now in southern Israel) and Faynan (biblical Punon, Jordan).[10]By 2000 BC, Europe was using bronze.[8] The use of bronze became so widespread in Europe approximately from 2500 BC to 600 BC that it has been named the Bronze Age. The transitional period in certain regions between the preceding Neolithic period and the Bronze Age is termed the Chalcolithic ("copper-stone"), with some high-purity copper tools being used alongside stone tools. Brass (copper-zinc alloy) was known to the Greeks, but only became a significant supplement to bronze during the Roman empire.
During the Bronze Age, one copper mine at Great Orme in North Wales, extended for a depth of 70 meters.[11] At Alderley Edge in Cheshire, carbon dates have established mining at around 2280 to 1890 BC (at 95% probability).[12]
Antiquity and Middle Ages
In alchemy the symbol for copper, perhaps a stylized mirror, was also the symbol for the goddess and planet Venus.
Chalcolithic copper mine in Timna Valley, Negev Desert, Israel.
Britain's first use of brass occurred around the 3rd - 2nd century B.C. In North America, copper mining began with marginal workings by Native Americans. Native copper is known to have been extracted from sites on Isle Royale with primitive stone tools between 800 and 1600.[14]
Copper metallurgy was flourishing in South America, particularly in Peru around the beginning of the first millennium AD. Copper technology proceeded at a much slower rate on other continents. Africa's major location for copper reserves is Zambia. Copper burial ornamentals dated from the 15th century have been uncovered, but the metal's commercial production did not start until the early 1900s. Australian copper artifacts exist, but they appear only after the arrival of the Europeans; the aboriginal culture apparently did not develop their own metallurgical abilities.
Crucial in the metallurgical and technological worlds, copper has also played an important cultural role, particularly in currency. Romans in the 6th through 3rd centuries B.C. used copper lumps as money. At first, just the copper itself was valued, but gradually the shape and look of the copper became more important. Julius Caesar had his own coins, made from a copper-zinc alloy, while Octavianus Augustus Caesar's) coins were made from Cu-Pb-Sn alloys.
The gates of the Temple of Jerusalem used Corinthian bronze made by depletion gilding. Corinthian bronze was most prevalent in Alexandria, where alchemy is thought to have begun.[15] In ancient India (before 1000 B.C.), copper was used in the holistic medical science Ayurveda for surgical instruments and other medical equipment. Ancient Egyptians (~2400 B.C.) used copper for sterilizing wounds and drinking water, and as time passed, (~1500 B.C.) for headaches, burns, and itching. Hippocrates (~400 B.C.) used copper to treat leg ulcers associated with varicose veins. Ancient Aztecs fought sore throats by gargling with copper mixtures.
Copper is also the part of many rich stories and legends, such as that of Iraq's Baghdad Battery. Copper cylinders soldered to lead, which date back to 248 B.C. to 226 A.D, resemble a galvanic cell, leading people to believe this may have been the first battery. This claim has so far not been substantiated.
The Bible also refers to the importance of copper: "Men know how to mine silver and refine gold, to dig iron from the earth and melt copper from stone" (Job. 28:1-2).
Modern period
Miners at the Tamarack Mine in Copper Country, Michigan, USA in 1905
Plating was a technology that began started in the mid 1600s in some areas. One common use for copper plating, widespread in the 1700s, was the sheathing of ships' hulls. Copper sheathing could be used to protect wooden hulled ships from algae, and from the shipworm "toredo", a saltwater clam. The ships of Christopher Columbus were among the earliest to have this protection.[16]
In 1801 Paul Revere established America's first copper rolling mill in Canton, Massachusetts. In the early 1800s, it was discovered that copper wire could be used as a conductor, but it wasn't until 1990 that copper, in oxide form, was discovered for use as a superconducting material. The German scientist Gottfried Osann invented powder metallurgy of copper in 1830 while determining the metal's atomic weight. Around then it was also discovered that the amount and type of alloying element (e.g. tin) would affect the tones of bells, allowing for a variety of rich sounds, leading to bell casting, another common use for copper and its alloys.
The Norddeutsche Affinerie in Hamburg was the first modern electroplating plant starting its production in 1876.[17]
Flash smelting, was developed by Outokumpu in Finland and first applied at the Harjavalta plant in 1949. The process makes smelting more energy efficient and is today used for 50% of the world’s primary copper production.[18]
Copper has been pivotal in the economic and sociological worlds, notably disputes involving copper mines. The 1906 Cananea Strike in Mexico dealt with issues of work organization. The Teniente copper mine (1904-1951) raised political issues about capitalism and class structure. Japan's largest copper mine, the Ashio mine, was the site of a riot in 1907. The Arizona miners' strike of 1938 dealt with American labor issues including the "right to strike".
Characteristics
Color
Copper just above its melting point keeps its pink luster color when enough light outshines the orange incandescence color.
Group 11 of the periodic table
Copper occupies the same family of the periodic table as silver and gold, since they each have one s-orbital electron on top of a filled electron shell which forms metallic bonds. This similarity in electron structure makes them similar in many characteristics. All have very high thermal and electrical conductivity, and all are malleable metals. Among pure metals at room temperature, copper has the second highest electrical and thermal conductivity, after silver.[21]Occurrence
Native copper (~ 4 cm in size)
Mechanical properties
Copper is easily worked, being both ductile and malleable. The ease with which it can be drawn into wire makes it useful for electrical work in addition to its excellent electrical properties. Copper can be machined, although it is usually necessary to use an alloy for intricate parts, such as threaded components, to get really good machinability characteristics. Good thermal conduction makes it useful for heatsinks and in heat exchangers. Copper has good corrosion resistance, but not as good as gold. It has excellent brazing and soldering properties and can also be welded, although best results are obtained with gas metal arc welding.[23]Copper is normally supplied, as with nearly all metals for industrial and commercial use, in a fine grained polycrystalline form. Polycrystalline metals have greater strength than monocrystalline forms, and the difference is greater for smaller grain (crystal) sizes. The reason is due to the inability of stress dislocations in the crystal structure to cross the grain bou