On exposure to moist air, copper gains a green coat on its surface due to formation of which one of the following compound?

When copper is exposed to moist air for a long period, it undergoes a slow chemical reaction with oxygen, water, and carbon dioxide present in the atmosphere. This process, known as corrosion or patina formation, initially produces a brownish layer of copper oxide. However, as the reaction continues with moisture and carbon dioxide, it forms a green coating on the surface. This green substance is primarily composed of basic copper carbonate, which is a mixture of copper carbonate (CuCO3) and copper hydroxide (Cu(OH)2). In nature, this compound is often found as the mineral malachite. While copper oxide is black and copper sulphate is typically blue, the characteristic green 'patina' seen on historical monuments like the Statue of Liberty is due to the formation of these carbonate compounds.