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CHEMICAL-PHYSICAL PROPERTIES
- Atomic number: 29
- Atomic weight: 63.55
- Electronic configuration: [Ar] 3d10 4s1
- Atomic radius (nm); 0.118
- 1st ionization potential (eV): 7.72
- Electrode Standard Potential (V): 0.158 (Cu++/Cu+)
- " " " : 0.521 (Cu+/Cu)
- Density (g/cc): 8.96
- Melting T (C): 1083
- Boiling T (C): 2595
- Oxidation number: +1 ; +2

PRESENCE IN NATURE AND PRODUCTION

Its name derives from the Latin "Cuprum" that on its turn, derives from the Cyprus Island, where, during the Roman Empire, the largest part of Cu was extracted.

In nature, it forms about the 0.007% of the Earth crust and it can be found either as pure metal and combined: its main minerals are CUPRITE (CuO), MALACHITE, CuCO3*Cu(OH)2, CHALCOPYRITE (CuFeS2), CALCOSINE (Cu2S).

It can be obtained mainly from OXIDES and CARBONATES, by reduction at high T with COKE (C), but the most important process is from the SULFIDE Cu2S; the first 2/3 of it are turned by O2 in oxide, that is reduced to Cu by the remaining sulfide:
2 Cu2S + O2 -> 2Cu2O + 2SO2
2 Cu2O + Cu2S -> 6Cu + SO2
Then, Cu is purified by electrolysis for the largest part of its production.

CHEMICAL PROPERTIES AND COMPOUNDS
- Cu has a typical red colour and is very ductile.
- It can be dissolved by an oxidant acid like HNO3:
3 Cu + 8 HNO3 -> 3 Cu(NO)3 + 2 NO + 4H2O
and also by H2SO4, but more slowly
These oxidation reactions are not due to the H+ ion that has a lower potential (0.0 V) than Cu; just for this, HCl can't attack it.
- Cu has 2 oxidation numbers, forming 2 ions: (cuprous ion, Cu+) and II (cupric ion, Cu++) and the compounds of the first are less stable, tending to be oxidated to Cu++ also by O2 of the air.

Cu+
- Cu2O: it's a yellow-red powder, produced reducing Cu++ salts in alkaline solutions with glucose, arsenious acid and so on.
- Cu+ solutions, like those of CuCl, tend to give a disproportion reaction:
2Cu+ -> Cu + Cu++
and to stabilize them it's necessary to form COMPLEX SALTS with halides(F-, Cl-, Br-,I-), NH3, CN-, and organic compounds
- Cu+ can be also stabilized precipitating it as insoluble salt:
2 Cu++ + 2 I- -> I2 + 2 CuI
CuI precipitates together I2 that can be easily separated

Cu++
- CuSO4*5H2O: it's the most important soluble salt of Cu and is dark blue at the solid state, due to the presence of water molecules in its crystals, directly bound with Cu++ ion.
If heated over 200 C, it loses all its water becoming WHITE.
Industrially, it's prepared dissolving Cu in hot H2SO4 diluted solution in presence of an air current, to provide oxidizing conditions;
2 Cu + O2 + 2 H2SO4 -> 2 CuSO4 + 2 H2O

- CuO: it's a black powder produced heating Cu powder, Cu(NO3)2 or CuCO3 in the air.
It can be obtained also by the HYDROXIDE Cu(OH)2, blue that, just precipitated with OH-, decomposes to CuO.
- Cu can form many complex salts with molecules and ions with an available electrons couple to put in the empty 4p orbitals of Cu++;
CuCl3- ; CuCl4- ; Cu(NH3)4++

USES
- Cu is mainly used very pure to produce the conductor wires for electricity, electronic components, coins, valves and parts of pumps and engines.
After Fe and Al, it is the most important metal for technology.
Half of the Cu is used in alloys like BRONZES (Cu > 70%; Sn < 30%)
ALUMINIUM BRONZES (Cu 80-95%; Al 5-15%) and BRASS (Cu 65-85%; Zn 15-35%).

- CuSO4*5H20 is used in agriculture against fungi and in industrial electrolysis to purify Cu and in galvanoplating to deposit Cu on metallic objects.

Learn more about this author, Aldo Bonincontro.
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