1. | A layer of cupric oxide on the surface of copper. |
2. | Basic copper sulphate layer on the surface of the metal |
3. | A layer of cupric hydroxide on the surface of copper |
4. | A layer of basic carbonate of copper on the surface of copper |
1. | \(SO^{2-}_3\) | 2. | \(NO^{-}_2\) |
3. | \(S^{2-}\) | 4. | All of the above |