Question

copper loses its luster and develops a green coating over it when exposed to the atmosphere

Answer 1

As when it is exposed to atmosphere, Oxidation reaction takes place and the copper loses its luster and develops a green coat.

Answer 2

Similar to iron and aluminum, the element copperundergoes the process of oxidation, if it is exposed to air. Over here, copper metal reacts with oxygen, resulting in the formation of copperoxide, which appears green in color. ... The outer green layer, formed after the oxidation of copper, is known as patina.