Copper is a very common transition metal that is hugely used in many industries to form alloys that are incorporated to make products that are of day to day essentials and are commercially viable including coins in currencies. In Chemistry, the copper chemical formula is denoted as Cu. as copper belongs to the transition metal group in the periodic table that has a d subshell and is denoted as (n - 1) d transition. It has an atomic number 29, thus the copper chemical formula is alternatively written as Cu29 in general. Copper is very soft, malleable, ductile and the fresh surface of copper exposed appears pinkish-orange in colour.
They are good conductors of electricity with high thermal conductivity and thus is widely used as metal in electric wiring. The various alloys are also used for making jewellery, where sterling silver is used, cupro nickel is used to make coins and marine hardware, thermocouples for temperature measurement and strain gauge copper alloy constantan is used. The raw metallic form of copper is illustrated below.
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Oxidation States of Copper
Though copper shows multiple oxidation states due to the presence of the d-subshells ranging from +1, +2,+3,+4 the most stable is the +2 oxidation state. The valence shell electron distribution of the transition metal copper is [Xe] 4s1 3d10. Thus the 4s subshell as 1 electron along with the 3d electrons together acts as valence shell electrons. Thus obtaining stable oxidation states refers to energy balance. Thus losing electrons from the valence shells requires energy and obtaining high oxidation means losing valence electrons that cost higher energy. Thus the energy costs for reaching a definite oxidation state needs to be compensated with the electron affinity of the nonmetal and the electrostatic forces of attraction of dipoles and negative ions bonding.
Thus copper metal can lose an additional single electron from 3d subshell with one 4s electron whose energy gets compensated but going of higher oxidation costs higher energy that is compensated with the electron affinity of nonmetal and the electrostatic forces of attraction of dipoles and negative ions and thus are unstable in nature. But for higher electronegative atoms like fluorine and oxygen that possess higher electron affinity produces a higher oxidation state of copper when a compound is formed. But most of the well-known copper compounds exhibit a +2 oxidation state of copper like CuSO4 which is a copper sulphate formula.
As the sulphate group in copper sulphate formula has a +2 oxidation state itself and there is just one atom of copper balancing out one atom of sulphate in copper sulphate formula. Thus it is clear that the oxidation state of CuSO4 is Cu (ll). Another common compound of copper Cu (ll) oxidation is a copper oxide or cupric oxide which is the CuO compound name. The chemically, copper oxide formula or cupric oxide formula CuO.
Production and Method
Most of the copper is extracted from the large pits of the porphyry copper reserve sites in the form of copper sulfides that contain about 0.5 - 1.0 % of copper. Most of these copper mines are situated in Chili, Utah in the United States and Mexico. Chilli has been one of the largest producers of copper ore in 2005, followed by the United States, Indonesia and Peru according to the British Geological Survey. Since 1900 the use of copper has been sharply increasing and with the net quantity of copper available around the globe it has been difficult to match up the use of copper as that of the usage of developed countries. Thus an alternative to copper has come into play which is polymetallic nodules also known as, manganese nodules that are recovered from the concentric layers of copper and manganese hydroxide present at the ocean bed.
Through many years since 1900, some of the methods are used for the extraction of copper. In order to recover copper from the nodules, methods like sulfuric leaching, smelting followed by the application of cuprion process is followed. Thus the copper present in the ores of the land is recovered to 10 - 15% copper by froth flotation and bleaching process. Thus in order to remove much of the iron present in the ore flash, melting of the material with silica is carried out so that iron is removed as slag. This method converts the iron sulfides into oxides that react with the silica to form a silicate slag that floats up to the surface of the heated material. Thus the left out copper matte is in the form of copper sulfide that is the Cu2S compound name, and is roasted to convert the sulfides into copper (l) oxide which is another copper oxide formula with +1 oxidation stage that is unstable in nature and readily decomposes on heating to pure copper.
2 Cu2S + 3 O2 → 2 Cu2O + 2 SO2
2 Cu2O → 4 Cu + O2
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Another process by which copper is synthesised in the laboratory is by reduction of CuO, the copper oxide formula. In this reaction, copper oxide gets reduced in presence of hydrogen where it loses its oxygen that gets attached to hydrogen to form water and is, therefore, also termed as hydrolysis of CuO.
CuO + H2 → Cu + H2O
Another viable process, copper sulfate formula is dropped in a container called autoclave and is pressurized with the hydrogen gas at 25 bar (where the pressure of H2 gas is around 30 bar). Then the copper sulfate solution (which is actually CuSO4 compound name) is heated at about 150 oC for about an hour that results in the formation of copper that will precipitate in the form of copper powder.
CuSO4 (aq) + H2 (g) → Cu(s) + H2SO4 (aq)
The physicochemical properties of copper are as follows:
Properties of Copper