Known Isotopes: by a69hDM0v

VIEWS: 8 PAGES: 12

									                         Copper Element

     Copper (element), symbol Cu, brownish-red metallic element
that is one of the most widely used of metals. Copper is one of
the transition elements in group eleven of the periodic table.
The atomic number of copper is 29. Copper has 29 electrons,
protons and neutrons and a mass of 64 amu. Copper is solid at
298 K.




Electron Configuration of Copper




Radioisotope data

This table gives information about some radiosotopes of copper,
their masses, their half-lives, their modes of decay, their
nuclear spins, and their nuclear magnetic moments.
Isotope   Mass    Half- Mode of decay Nuclear Nuclear magnetic
                   life                  spin         moment
 59
   Cu   58.939504    1.36 m   EC to 59Ni       3
                                                /2
 60
   Cu   59.937368    23.7 m   EC to 60Ni        2          1.219
 61
   Cu   60.933462    3.35 h   EC to 61Ni       3
                                                /2         2.14
 62
   Cu   61.932587    9.74 m   EC to 62Ni        1         -0.380
 64                  12.701 EC to 64       -
   Cu   63.929768                              1          -0.217
                         h      to 64Zn
 66                            -
   Cu   65.928873    5.09 m      to 66Zn        1         -0.282
 67                            -
   Cu   66.92775    2.580 d      to 67Zn       3
                                                /2
 68                            -
   Cu   67.92964       31 s      to 68Zn        1
 69                            -
   Cu   68.92943      2.8 m      to 69Zn       3
                                                /2



      Copper was known to prehistoric people and was probably the
first metal from which useful articles were made. One of the
first metals known to humans, free copper was probably mined in
the Tigris-Euphrates valley as long ago as the 5th cent. B.C.
Cyprus, from which the metal’s name originally comes, was the
primary source of copper in the ancient world.       Copper objects
have been found among the remains of many ancient civilizations,
including those of Egypt, Asia Minor, China, southeastern
Europe, Cyprus (from which the word copper is derived), and
Crete (Kríti). It was known to Native Americans, and American
ores were found by the European explorers. It is also found in
the pure state.
      Copper melts at about 1083° C (about 1981° F), boils at
about 2567° C (about 4753° F), and has a specific gravity of
8.9. The atomic weight of copper is 63.546. Density of solid
copper is 8920 kg/m-3.    Natural copper is a mixture of two stable
isotopes: copper-63 (69.17 percent) and copper-65 (30.83
percent).

  Copper is one of the most ductile metals, not especially
strong or hard. Strength and hardness are appreciably increased
by cold-working because of the formation of elongated crystals
of the same face-centered cubic structure that is present in the
softer annealed copper. Common gases, such as oxygen, nitrogen,
carbon dioxide, and sulfur dioxide are soluble in molten copper
and greatly affect the mechanical and electrical properties of
the solidified metal.




    Because of its many desirable properties, such as its
conductivity of electricity and heat, its resistance to
corrosion, its sectility , its malleability and ductility, and
its beauty, copper has long been used in a wide variety of
applications. Copper has a face-centered cubic crystalline
structure.   It is an extremely good conductor of both heat and
electricity.   It is softer than iron but harder than zinc and
can be polished to a bright finish.   The principal uses are
electrical, because of copper's extremely high conductivity,
which is second only to that of silver.   Because copper is very
ductile, it can be drawn into wires of any diameter from about
0.025 mm (about 0.001 in) upward. The tensile strength of drawn
copper wire is about 4200 kg/sq cm (about 60,000 lb/sq in); it
can be used in outdoor power lines and cables, as well as in
house wiring, lamp cords, and electrical machinery such as
generators, motors, controllers, signaling devices,
electromagnets, and communications equipment.
Thermodynamic properties



 State       fHä           fGä                Sä                  CpH       Hä298.15-Hä0
                   -1             -           -1         -1
         /kJ mol        /kJ mol        /J K        mol        /J K-1 mol-    /kJ mol-1
                           1                                       1

                                                                             *5.004 ±
 Solid       *0            0          *33.15 ± 0.08             24.43
                                                                               0.008
          *337.4 ±                     *166.398 ±                            *6.197 ±
  Gas                    298.6                                  20.79
             1.2                          0.004                                0.001
  Gas
           484.2         432.0            241.5                  36.6          9.92
 (Cu2)



    Copper has been used for coins throughout recorded history
and has also been fashioned into cooking utensils, vats, and
ornamental objects. Copper was at one time used extensively for
sheathing the bottom of wooden ships to prevent fouling. Copper
can easily be electroplated, alone or as a base for other
metals. Large amounts are used for this purpose, particularly in
making electrotypes, reproductions of type for printing.
   The metallurgy of copper varies with the composition of the
ore. Native copper is crushed, washed, and cast in bars. Oxides
and carbonates are reduced with carbon. The most important ores,
the sulfides, contain not more than 12 percent, sometimes as
little as 1 percent, of copper; they must first be crushed and
concentrated by flotation. The concentrates are smelted in a
reverberatory furnace, which yields crude metallic copper,
approximately 98 percent pure. Crude copper is further purified
by electrolysis, yielding bars exceeding 99.9 percent purity.
    Pure copper is soft but can be hardened somewhat by being
worked. Alloys of copper, which are far harder and stronger than
the pure metal, have higher resistance and so cannot be used for
electrical purposes. They do, however, have corrosion resistance
almost as good as that of pure copper and are very easily worked
in machine shops. The two most important alloys are brass, a
zinc alloy, and bronze, a tin alloy. Both tin and zinc are
sometimes added to the same alloy, and no sharp dividing line
can be drawn between brass and bronze. Both are used in enormous
quantities. Copper is also alloyed with gold, silver, and
nickel, and is an important constituent of such alloys as Monel
metal, gunmetal, and German silver.
    Copper forms two series of chemical compounds: cuprous, in
which the copper has a valence of 1, and cupric, in which the
copper has a valence of 2. Cuprous compounds are easily oxidized
to cupric, in many cases by mere exposure to air; cupric
compounds are stable. Certain copper solutions have the power of
dissolving cellulose, and large quantities of copper are for
this reason used in the manufacture of rayon. Copper is also
used in many pigments and in such insecticides as Paris green
and such fungicides as Bordeaux mixture, although it is being
largely replaced by synthetic organic chemicals for these
purposes.
    Native copper occurs in the vicinity of Lake Superior in
northern Michigan, where it is mined in economically important
quantities; it occurs also in small amounts in other parts of
the world. Overall, copper is about the 25th most abundant
element in crustal rocks. It is usually found admixed with other
metals, such as gold, silver, bismuth, and lead, and exists in
small specks in rock, but individual masses weighing as much as
420 metric tons have been found. The principal sources of copper
are chalcopyrite and bornite, mixed sulfides of copper and iron.
Other important ore minerals are chalcocite and covellite,
sulfides of copper, which are found in Arizona and Nevada in the
United States and in Cornwall, England. Copper ores are also
found in Canada, South America (in Chile and Peru), S central
Africa, Russia (in the Ural Mts.), and to a limited extent in
Europe and the British Isles.   Enargite, a sulfarsenate of
copper, is found in various parts of the United States. Azurite,
a basic carbonate of copper, is found in France and Australia,
and malachite, also a basic carbonate of copper, in the Ural
Mountains. Tetrahedrite, a sulfantimonide of copper and various
other metals, and chrysocolla, a copper silicate, are both
widely distributed. Cuprite, an oxide, is found in Cuba, and
atacamite, a basic chloride, in Peru.
    The principal ore of copper is chalcopyrite, a sulfide of
copper and iron, also called copper pyrite. Other important ores
are chalcocite, or copper glance, a shiny lead-gray copper
sulfide; bornite, a lustrous reddish-brown sulfide of copper and
iron; cuprite, a red cuprous oxide ore; and malachite, a bright
green carbonate ore. Azurite is a blue crystalline basic
carbonate of copper found with other copper ores. Chrysocolla is
a bluish-green copper silicate ore. Another important source of
copper is secondary (scrap) copper, which is produced from
discarded copper and copper alloys.
    U.S. production of copper in 1991 was about 18.5 percent of
 the estimated world production of 8.8 million metric tons. The
 leading ore-producing states are Arizona, New Mexico, and Utah.
     Copper is present in minute amounts in the animal body and
is essential to normal metabolism. It is a component of
hemocyanin, the blue, oxygen-carrying blood pigment of lobsters
and other large crustaceans. It is needed in the synthesis of
hemoglobin, the red, oxygen-carrying pigment found in the blood
of humans, although it is not a component of hemoglobin.

     The chief commercial use of copper is based on its
electrical conductivity (second only to that of silver); about
half the total annual output of copper is employed in the
manufacture of electrical apparatus and wire. Copper is also
used extensively as roofing, in making copper utensils, and for
coins and metalwork. Copper tubing is used in plumbing, and,
because of its high heat conductivity, in heat-exchanging
devices such as refrigerator and air-conditioner coils. Powdered
copper is sometimes used as a pigment in paints. An important
use of copper is in alloys such as brass, bronze, gunmetal,
Monel metal, and German silver. Compounds of copper are widely
used as insecticides and fungicides; as pigments in paints; as
mordants (fixatives) in dyeing; and in electroplating.
 Two important kinds of copper ore are contained in this sample:
 chalcopyrite (top) and bornite (bottom). Copper ore is found
 throughout the world, but the low percentage of metal obtained from
 the ore and the often hard-to-access location of deposits make many
 potential mines uneconomic. Copper is the second most-used metal in
 the world and is valued for its conductivity, malleability, resistance
 to corrosion, and beauty.
     The most important chemical compound of copper is copper
sulfate pentahydrate, also called bluestone or blue vitriol.
Other compounds include Paris green, Bordeaux mixture, a
cyanide, a chloride, oxides, and a basic carbonate. Verdigris is
basic copper acetate.


     Copper metal is prepared commercially in various ways.
Copper sulfide ores, usually containing only 1% to 2% copper,
are concentrated to 20% to 40% copper by the flotation process.
Milling begins when a crusher reduces copper ore to small
pieces. Water is added to form a mixture called slurry. A ball
mill grinds the crushed ore in the slurry into fine particles.
The particles become concentrated in a flotation cell. They are
then usually roasted to remove some of the sulfur and other
impurities, and then smelted with iron oxide in either a blast
furnace or a reverberatory furnace to produce copper matte, a
molten solution of copper sulfide mixed with small amounts of
iron sulfide. Smelting removes many impurities from the copper
concentrate. A flash furnance eliminates impurities in the form
of gases and slag (solid waste), producing copper matte. A
converter further purifies the molten copper. The matte is
transferred to a converter, where it is treated by blowing air
through it to remove the sulfur (as sulfur dioxide, a gas) and
the iron (as a slag of ferrous oxide). The resulting copper is
98% to 99% pure; it is called blister copper because its surface
is blistered by escaping gases when it solidifies during
casting. Final processing consists of melting and casting the
copper metal into cakes, billets, rods, and ingots. Such forms
are used to manufacture various copper products, including
kitchen utensils, pipes, wires, and brass hinges.
     Most copper is further purified by electrolysis. The
blister copper is refined in a furnace and cast into anodes.
Thin sheets of pure copper are used as cathodes. A solution of
copper sulfate and sulfuric acid is used as the electrolyte.
When the anode and cathode are immersed in the electrolyte and
an electric current is passed, the anode is dissolved in the
electrolyte and pure copper metal is deposited on the cathode.
Soluble impurities, usually nickel and arsenic, remain dissolved
in the electrolyte. Insoluble impurities, often including
silver, gold, and other valuable metals, settle out of the
electrolyte; they may be collected and purified.
     Copper oxide ores are usually treated by a different
process, called leaching, in which the copper in the ore is
dissolved in a leaching solution (usually dilute sulfuric acid);
pure copper is recovered by electrolysis. Alternatively, the
solution is treated with iron to precipitate the so-called
cement copper, which is impure.

How Copper Metal is Produced
 Geologists had located large ore deposits in the United States
and Chile. But the copper content of the ore was so low that
the ore could not be processed at a profit. About 1900, a young
American mining engineer in Utah, Daniel C. Jackling, realized
that low-grade ores could be processed cheaply by using mass-
production methods. His process involved the use of steam
shovels to strip off surface rock. Other special mass-
production equipment was used for smelting and refining. New
techniques for separating copper from the ore also increased
the supply of available copper.

     Copper is readily recycled from scrap wire, motors,
automobile radiators, and electronic equipment. Recycled scrap
supplies about one-fourth of the U.S. copper requirement.
                 Bibliography




http://www.askjeeves.com, 2/14/01
http://www.bartleby.com/65/co/copper.html, 2/12/01
http://www.britannica.com/bcom/eb/article/7/0,5716,26617+2+26194
,00.html?query=element%20copper, 2/13/01
http://encarta.msn.com/find/Concise.asp?ti=026C2000, 2/12/01

								
To top