| Characteristics of copper |
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Copper has a reddish, orangish, or brownish color because a thin layer of tarnish including oxides gradually forms on its surface when gases especially oxygen in the air react with it. But pure copper, when fresh, is actually a pinkish or peachy metal. Copper and gold are the only two elemental metals with a natural color other than gray or silver. The usual gray color of metals depends on their electron sea that is capable of absorbing and reemitting photons over a wide range of frequencies. Copper has its characteristic color because of its band structure. In its liquefied state, a pure copper surface without ambient light appears somewhat greenish, a characteristic shared with gold. When liquid copper is in bright ambient light, it retains some of its pinkish luster.Copper occupies the same family of the periodic table as silver and gold, since they each have one sorbital 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.
The periodic table of the chemical elements is a tabular method of displaying the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in . Mendeleev intended the table to illustrate recurring periodic trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior.The periodic table is now ubiquitous within the academic discipline of chemistry, providing an extremely useful framework to classify, systematize and compare all of the many different forms of chemical behavior. The table has also found wide application in physics, biology, engineering, and industry. The current standard table contains elements as of January .Mainly, gold appears to be metallic yellow. Gold, caesium and copper are the only elemental metals with a natural color other than gray or white. The usual gray color of metals depends on their electron sea that is capable of absorbing and reemitting photons over a wide range of frequencies. Gold reacts differently, depending on subtle relativistic effects that affect the orbitals around gold atoms.
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Mechanical properties
A single crystal copper consists of a few micrometres of small crystals. In this form of crystal c, the yield stress is high and crystal undergoes a large amount of elastic deformation before going into the plastic deformation region. The plastic deformation region has an unpredictable outcome. The stress level decreases significantly as necking begins to occur.
Polycrystal copper has many crystal of different geometries combined. The plastic deformation of polycrystal is similar to mild steel. Copper has a high ductility and will continue to elongate as stress is applied. It is very useful in copper wire drawing.Numerous copper alloys exist, many with important historical and contemporary uses. Speculum metal and bronze are alloys of copper and tin. Brass is an alloy of copper and zinc. Monel metal, also called cupronickel, is an alloy of copper and nickel. While the metal bronze usually refers to coppertin alloys, it also is a generic term for any alloy of copper, such as aluminium bronze, silicon bronze, and manganese bronze.
The similarity in external appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing the different compositions. There are as many as different copper and copperalloy compositions loosely grouped into the categories copper, high copper alloy, brasses, bronzes, copper nickels, copper–nickel–zinc nickel silver, leaded copper, and special alloys. The following table lists the principal alloying element for four of the more common types, along with the name for each type.Cupronickel Sometimes incorrectly written as Cupernickel or Coppernickel is an alloy of copper, nickel and strengthening impurities, such as iron and manganese. Cupronickel does not corrode in seawater, because its electrode potential is adjusted to be neutral with regard to seawater. Because of this it is used for marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats.A common use is in many silvercoloured modern circulation coins. A typical mix is copper, nickel, and a trace amount of manganese. In the past true silver coins were debased with cupronickel. Despite high copper content the colour of cupronickel is silver.It is used in thermocouples, and a copper nickel alloy is used to make very accurate resistors.
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Corrosion
Copper is a metal that does not react with water HO, but the oxygen of the air will react slowly at room temperature to form a layer of brownblack copper oxide on copper metal.
The Pourbaix diagram for copper in pure water, perchloric acid or sodium It can be seen that copper in pure water is more noble than hydrogen. As a result it does not corrode in oxygen free water and the corrosion rate in oxygenated water is low. hydroxideIt is important to note that in contrast to the oxidation of iron by wet air that the layer formed by the reaction of air with copper has a protective effect against further corrosion. On old copper roofs a green layer of copper carbonate, called verdigris, can often be seen. Another notable example of this is on the Statue of Liberty.Copper should not be in only mechanical contact with metals of different electropotential for example, a copper pipe joined to an iron pipe, especially in the presence of moisture, as the completion of an electrical circuit as through the common earth ground will cause the juncture to act as an electrochemical cell as is a single cell of a battery. The weak electrical currents themselves are harmless but the electrochemical reaction will cause the conversion of the iron to other compounds, eventually destroying the functionality of the union.
This problem is usually solved in plumbing by separating copper pipe from iron pipe with some nonconducting segment usually plastic or rubber.Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when in electrical contact with a different type of metal and both metals are immersed in an electrolyte. Conversely, a galvanic reaction is exploited in primary batteries to generate a voltage. A common example is the carbonzinc cell where the zinc corrodes preferentially to produce a current. The lemon battery is another simple example of how dissimilar metals react to produce an electric current.
Rusted corrugated steel roof .When two or more different sorts of metal come into contact in the presence of an electrolyte a galvanic couple is set up as different metals have different electrode potentials. The electrolyte provides a means for ion migration whereby metallic ions can move from the anode to the cathode. This leads to the anodic metal corroding more quickly than it otherwise would the corrosion of the cathodic metal is retarded even to the point of stopping. The presence of electrolyte and a conducting path between the metals may cause corrosion where otherwise neither metal alone would have corroded.
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Sulfide media
Copper metal does react with hydrogen sulfide and sulfidecontaining solutions. A series of different copper sulfides can form on the surface of the copper metal.Note that the copper sulfide area of the plot is very complex due to the existence of many different sulfides, a close up is also provided to make the graph more clear. It is clear that the copper is now able to corrode even without the need for oxygen as the copper is now less noble than hydrogen. This can be observed in everyday life when copper metal surfaces tarnish after exposure to air which contains sulfur compounds.Aqueous solutions of transition metals cations react with sulfide sources HS, NaSH, NaS to precipitate solid sulfides. Such inorganic sulfides typically have very low solubility in water and many are related to minerals. One famous example is the bright yellow species CdS or cadmium yellow. The black tarnish formed on sterling silver is AgS. Such species are sometimes referred to as salts. In fact the bonding in transition metal sulfides is highly covalent, which gives rise to their semiconductor properties, which in turn is related to the practical applications of many sulfide materials.
In organic chemistry, sulfide usually refers to the linkage CSC, although the term thioether is less ambiguous. For example, the thioether dimethyl sulfide is CHSCH. Polyphenylene sulfide see below has the empirical formula CHS. Occasionally, the term sulfide refers to molecules containing the SH functional group. For example, methyl sulfide can mean CHSH. The preferred descriptor for such SHcontaining compounds is thiol or mercaptan, i.e. methanethiol or methyl mercaptan.Confusion arises from the different meanings of the term disulfide. Molybdenum disulfide consists of separated sulfide centers, in association with molybdenum in the formal oxidation state. Iron disulfide on the other hand consists of S, or SS, in association with iron in the formal oxidation state. Dimethyldisulfide has the connectivity CHSSCH, whereas carbon disulfide has no SS linkages, being SCS.
Production
In , Chile was the top mine producer of copper with at least onethird world share followed by the USA, Indonesia and Peru, reports the British Geological Survey.Most copper ore is mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits that contain . to . percent copper. Examples include Chuquicamata in Chile and El Chino Mine in New Mexico. The average abundance of copper found within crustal rocks is approximately ppm by mass, and ppm by atoms.The Intergovernmental Council of Copper Exporting Countries CIPEC, defunct since , once tried to play a similar role for copper as OPEC does for oil, but never achieved the same influence, not least because the secondlargest producer, the United States, was never a member. Formed in , its principal members were Chile, Peru, Zaire, and Zambia.Copper has been in use at least , years, but more than percent of all copper ever mined and smelted has been extracted since . And as India and China race to catch up with the West, copper supplies are getting tight. Copper is among the most important industrial metals. Like fossil fuels, copper is a finite resource. Peak copper is the point in time at which the maximum global copper production rate is reached, according to Hubbert peak theory, the rate of production enters its terminal decline.
Peak copper is the point in time at which the maximum global copper production rate is reached. Since copper is a finite resource, at some point in the future production will cease, and at some earlier time production will reach a maximum. When this will occur is a matter of dispute. Unlike fossil fuels, though, copper is scrapped and reused. Copper is among the most important industrial metals. Copper is used in electrical power cables, data cables, electrical equipment, automobile radiators, cooling and refrigeration tubing, heat exchangers, artillery shell casings, water pipes, and jewellery.Copper has been in use at least , years, but more than percent of all copper ever mined and smelted has been extracted since . As India and China race to catch up with the West, the copper supply chain is becoming more strained, leading to increased prices and an increase in copper theft.North America alone mined million metric tons of the reddishbrown metal. |
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