When copper (Cu) metal piece is heated with chlorine gas, copper is oxidized to its highest oxidation state (+2) and chlorine gas is reduced to chloride ions. As the product, copper(II) chloride is given.
When metals which have variable oxidation numbers, react with halogens, those metals are oxidized to their higher oxidation state.
M is the metal which has variable oxidation numbers and X2 is the halogen. n is the highest oxidation number M metal can show. For copper this is +2 and for iron this is +3.
Copper is a metal which has variable oxidation numbers (+1 and +2). With reaction of chlorine, copper is oxidized to its maximum oxidation state, copper +2 ion. As the product, copper(II) chloride is given.
To happen the reaction, copper metal is heated. Copper is a red brown metal. Produced copper(II) chloride (CuCl2) is yellow colour in anhydrous state.
Chlorine is a pale green colour gas.
But, when CuCl2 dissolve in water, a blue colour solution is given.
In CuCl, copper is at its +1 oxidation state.
You learnt that, copper is oxidized to its +2 oxidation state when it reacts with chlorine. So we cannot prepare CuCl by this reaction directly. But we can reduce Cu2+ ion to Cu+ ion by a potassium iodide solution.
When potassium iodide is added to copper chloride solution, iodide ion is oxidized to iodine. With that, copper +2 ion is reduced to copper +1 ion by forming CuCl.
CuCl is insoluble in water and form a white precipitate.
Copper is oxidized to +2 oxidation state from 0 oxidation state while Chlorine is reduced from 0 to -1.
Sodium is much more reactive metal than Copper. Therefore, Copper does not react with Chlorine gas as Sodium does. A heating source is required to initiate the reaction between Copper and Chlorine gas.
Copper does not react with aqueous hydrogen chloride. Copper is located below hydrogen in electrochemical series and copper is not oxidized by dilute acids.
Copper is a metal and it removes it's last shell electron to form cation. To form +2 cation of copper, two electrons are removed from an atom. Chlorine forms -1 anion, chloride ion, by taking one electron removed by copper atoms.
You know, copper can show two oxidation numbers, +1 or +2. In the chemical formula, there is two chloride anions which are joint with a copper cation. Chlorine belongs to halogen group series and their oxidation number is -1 when they form compounds with metals such as NaCl, MgCl2, CaBr2.
Chlorine can show oxidation numbers of -1, 0, +1, +3, +5 and +7. So, chlorine's only negative oxidation number od -1.