The decay of metals by atmospheric oxygen and moisture is called corrosion. Few metals do not react with atmospheric gases and water and do not undergo corrosion, while others develop a dull layer on them or a coloured layer to spoil their shiny appearance or turn black or are converted into powder. few elements, on the other hand are protected due to presence of this dull layer of oxide on them.
Q. The green layer developed on copper on exposure to air is due to

Options

A. copper carbonate layer
B. basic copper carbonate layer
C. copper sulphate layer
D. copper nitrate layer.

Explanation

To answer the question regarding the green layer developed on copper when exposed to air, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Corrosion**: Corrosion is the process where metals react with atmospheric gases and moisture, leading to deterioration. Copper is one such metal that undergoes corrosion when exposed to air.

2. **Identifying the Reaction**: When copper (Cu) is exposed to moist air, it reacts with water (H2O), carbon dioxide (CO2), and oxygen (O2). This reaction leads to the formation of compounds.

3. **Chemical Reaction**: The reaction can be represented as:
\[ 2 \text{Cu} + \text{H}_2\text{O} + \text{CO}_2 + \text{O}_2 \rightarrow 2 \text{Cu(OH)}_2 + \text{CuCO}_3 \]
Here, copper hydroxide (Cu(OH)₂) and copper carbonate (CuCO₃) are formed.

4. **Formation of the Green Layer**: The green layer that develops on copper is primarily composed of basic copper carbonate, which is a result of the reaction mentioned above.

5. **Conclusion**: Therefore, the green layer developed on copper due to exposure to air is known as a basic copper carbonate layer.

### Final Answer:
The green layer developed on copper on exposure to air is due to **B. Basic Copper Carbonate Layer**.

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