Assertion : Formula of calcium oxide is CaO.
Reason : Symbol of calcium is Ca and its charge is +2 and charge on oxide is -2.

Options

A. If both assertion and reason are true and reason is the correct explanation
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the formula of calcium oxide is CaO.
- This is correct because calcium oxide is indeed represented by the formula CaO.

2. **Understanding the Reason**:
- The reason states that the symbol of calcium is Ca and its charge is +2, while the charge on the oxide ion is -2.
- This is also correct. Calcium (Ca) has a charge of +2 because it loses two electrons to achieve a stable electron configuration. The oxide ion (O) has a charge of -2 because it gains two electrons.

3. **Deriving the Formula**:
- To derive the formula of calcium oxide, we need to consider the charges of the ions involved.
- Calcium ion (Ca²⁺) has a charge of +2, and the oxide ion (O²⁻) has a charge of -2.
- When combining these ions to form a neutral compound, we need one calcium ion and one oxide ion to balance the charges:
- Ca²⁺ + O²⁻ → CaO.

4. **Conclusion**:
- Since both the assertion and the reason are correct, and the reason correctly explains the assertion, we conclude that the assertion is true and the reason is a correct explanation of the assertion.

### Final Answer:
- Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

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