Copper is a chemical element with the symbol Cu. It is found in many salts like copper sulphate, copper chloride and copper carbonate as Copper (II) ion. In group II, copper (II) ions are precipitated as their sulphides by passing hydrogen sulphide gas through their solution. Copper (II) ions produce a deep blue coloured complex on reaction with ammonium hydroxide and the blue coloured complex then reacts potassium ferrocyanide to form a chocolate brown precipitate of copper ferrocyanide.
This video explains how to test for the presence of copper (II) ion in a given salt.