Silver articles and copper get a black and green coating respectively when kept for longer time.in air. Mention the reason for this and identify the chemical name of coating in each case.

Silver articles react with gases in the atmosphere and form a coating of Silver Sulphide over them and get tarnished. Copper articles get a coating of Copper Carbonate which tarnishes them. Although in rare cases there is development of Copper Oxides too.

Silver article get black due to sunlight called thermal decomposition and copper get black because heat and oxygen hence it called copper oxide and ..

It Is due to the phenomenon called corrosion. When silver is exposed to the atmosphere then hydrogen sulphide (H2S) is formed giving it a black coated surface. In the case of copper, it reacts with moist carbon dioxide in atmosphere and forms copper carbonate (CuCo3)which gives a green coating to the copper article