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Copper

Copper Periodic Table Facts

Copper (Cu), chemical element, soft, tough, malleable, and reddish-brown metal of Group 11 or IB of the periodic table with high electrical and thermal conductivity. The metal copper form an fcc crystal lattice found the free metallic state in the environment. The native copper was fairly abundant in nature and the extraction could be easily from its ores. The metal and its alloy like bronze (copper + tin) are used in history for mankind from the Bronze age (3500 BCE) in Neolithic and Mesopotamia civilization. Copper is present in hemocyanin of blood of cuttlefish helps for the formation of hemoglobin (an oxygen carrier) in the animal body,  also present in plants like green peas.

Archaeological discovered the island of Cyprus in the eastern Mediterranean Sea (3500 BC) famous for the mines of copper. The name copper derived from the Latin name Cuprum via Cyprium with chemical symbol Cu, atomic number 29, atomic weight 63.546, meting point 1084.6 °C, boiling point 2560 °C, density 8.95 gm cm-3, and valence shell electron configuration of the atom [Ar] 3d10 4s1. The physical and chemical properties of high melting and density coinage or noble metals (copper, silver, gold family) are very similar in chemistry.

Occurrence of Elements in Earth’s Crust

Copper present in the earth’s crust to the extent of 68 ppm, slightly less than that of nickel. The native copper (minerals of basaltic leaves) and the reduced form of metal compounds like sulfide, carbonates, arsenide, and chloride are found in many locations of the world. The major ore of the metal is copper glance or chalcopyrite (CuFeS2), the other common ores like cuprite (Cu2O), chalcocite (Cu2S) malachite [CuCO3, Cu(OH)2] are largely found in North or South America, Chile (world’s leading producer), Congo, and Russian counties. In India, two main deposits of Cu ore are present in Bihar (Singhbhum) and Rajasthan (Alwar, Ajmer, and Khetri).

Extraction of Element

The elemental Copper mainly extracted from low grade ( 0.5 percent Cu) and high grade (15 to 20 percent of Cu) sulfide ore by the self-reduction process. The ore is fist crusted and concentrated by the forth-floatation process. The ore is then roasted in a current of air to remove arsenic and antimony. The roasted ore then melting (1400 °C) with the addition of silica in a reverberatory furnace. The iron oxide forms slags with silica. The molten mass separates from the top layer as a slug (FeSiO3), the lower surface contains copper matte-like Cu2S and FeS.

The molten matte is further oxidized by air blast in a converter (Bessemer converter) to oxidize the remaining iron in molten matte. More silica added which forms slag containing iron oxide. After removing slag, the metal sulfide oxidized by air to form Cu2O which combines with the remaining Cu2S to produce copper (Cu2S + 2Cu2O → 6Cu + SO2). The crude element is refining by electrolysis in a bath of acidified sulfate solution using the crude element as an anode and pure copper as a cathode. The impurities from the anode slime use for the recovery of gold, silver, and platinum.

Chemical Properties of Copper

A consequence of both the alkali family (lithium, sodium, potassium, rubidium, and cesium) and the currency or coinage metal (copper, silver, gold) has one electron in the outermost s-orbital and +1 is the common oxidation number or state. But the physical and chemical properties of these two groups vary widely, the alkali metals are soft, low melting, low density highly electropositive elements while coinage or noble metals (copper, silver, and gold) are relatively high melting point and high density. The group 13 or group 1B metals have high first ionization energy and smaller ionic radii. The Cu (II) ion is more stable than Cu (I) ion in water solution due to the small size and hence enormously high hydration energy of Cu (II) over that of Cu (I) which offsets the second ionization energy of copper.

Chemical Compounds of Copper

In learning chemistry, copper (I) has the closed-shell 3d10 configuration highly stabilizes by exchange energy, and the solid compounds in this state thermodynamically stable at moderate temperature. Therefore, Cu2O is formed at high temperatures from CuO and CuBr2 decomposes on heating to form CuBr and a large number of colorless, diamagnetic chemical compounds form in +1 state.

The +2 oxidation state is the main oxidation state of copper contain d9 configuration and form different types of oxide, hydroxide, halides, sulfate, carbonate, nitrate, and complex compounds. Black color oxide (CuO) formed by heating copper with oxygen but the thermal decomposition of carbonate, nitrate, or hydroxide is the best way to prepare CuO. Only white fluoride,  yellow chloride, and black bromide are known in a +2 oxidation state. Due to reduction properties, iodine reduces CuI2 to form Cu2I2. Copper sulfate (CuSO4, 5H2O) is prepared by dissolving scarp element in dilute sulfuric acid in presence of air and crystallizing. The nitrate is obtained as a deep blue deliquescent crystalline solid, Cu(NO3)3, 3H2O by the action of nitric acid in Cu (II) solution.

Due to the larger size and higher value of the sum of the first, second, and third ionization energy, copper in +2 state forms a few chemical compounds. There are no simple examples of halides but pale green K3CuF6 may be obtained by the action of fluorine in a mixture of KCl and CuCl2 at 250 °C. The solid cuprate (III) compounds like KCuO2 formed on heating the mixture of copper oxide (CuO) with alkali metal superoxide in presence of oxygen molecule.

Uses of Copper

Copper is a good conductor of electricity and extensively used in making wires, cables, generators, transformers, motors, and any other electrical equipment. It also used for making utensils, pipes, and currency coins but in the currency field, aluminum, stainless steel, and other alloys getting popular. Copper alloys like brass, bronze, constantan, manganin, and monal metal are extensively used for various domestic and industrial purposes due to high mechanical strength and corrosion resistance.

Brasses contain 57 to 97 percent copper, the remaining being zinc and a small number of other elements like Al, Sn, Ni, and Pb to modify the mechanical strength and chemical properties, which is largely used in domestic equipment, statues, ship propellers, and bearings. For example, Brass (70 percent of Cu and 30 percent of Zn), Delta metal ( 80 percent of Cu and 20 percent of Sn). Cupronickel (10 to 30 percent nickel and remaining being copper) has high tensile strength and resistant to chemical corrosion, rust, and acid used in chemical plants, telephonic systems, turbine blades, etc.