Calcium is tarnished in air , because it is covered with a thin film of

Options

A. oxide
B. hydroxide
C. carbonate
D. basic carbonate

Answer

To solve the question "Calcium is tarnished in air because it is covered with a thin film of," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Tarnishing**:
- Tarnishing refers to the formation of a thin layer of corrosion on metals when they react with substances in their environment. This often occurs due to exposure to air or moisture.

**Hint**: Remember that tarnishing is a chemical reaction that leads to the formation of a protective layer on metals.

2. **Identify the Metal in Question**:
- The metal mentioned in the question is calcium. Calcium is known to be a highly reactive alkaline earth metal.

**Hint**: Consider the properties of alkaline earth metals and their reactivity with air.

3. **Chemical Reaction with Air**:
- When calcium is exposed to air, it reacts with oxygen. This reaction leads to the formation of calcium oxide (CaO), which is a thin film that covers the surface of the calcium.

**Hint**: Think about what happens when metals react with oxygen in the air.

4. **Conclude the Type of Film Formed**:
- The thin film that forms on calcium due to its reaction with oxygen is specifically an oxide layer. This oxide layer protects the underlying metal from further corrosion.

**Hint**: Recall that oxides are common products of metal reactions with oxygen.

5. **Final Answer**:
- Therefore, the correct answer to the question is that calcium is tarnished in air because it is covered with a thin film of **oxide**.

### Summary of the Answer:
Calcium is tarnished in air because it is covered with a thin film of **oxide**.