Assertion:Atomic number is a more fundamental property of an element than its atomic mass.
Reason:Atomic number is equal to number of protons in an atom.

Options

A. If both assertion and reason is the correct explanation of assertion.
B. If both assertion and reason is the correct explanation of assertion.
C. If both assertion and reason is the correct explanation of assertion.
D. If both assertion and reason is the correct explanation of assertion.

Explanation

To solve the question, we need to analyze the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Atomic number is a more fundamental property of an element than its atomic mass."
- Atomic number (Z) is defined as the number of protons present in the nucleus of an atom. It uniquely identifies an element and determines its position in the periodic table.

2. **Understanding the Reason**:
- The reason states that "Atomic number is equal to the number of protons in an atom."
- This statement is true because the atomic number is indeed defined as the number of protons in the nucleus of an atom.

3. **Analyzing the Relationship**:
- The assertion claims that atomic number is more fundamental than atomic mass. This is correct because atomic number determines the chemical properties and behavior of an element, while atomic mass can vary due to isotopes and does not provide a consistent basis for classification.
- The reason correctly explains what atomic number is, but it does not explain why it is considered more fundamental than atomic mass.

4. **Conclusion**:
- Both the assertion and the reason are true statements. However, the reason does not provide a correct explanation for the assertion. Therefore, the correct choice is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
The correct answer is: Option 2 - Both assertion and reason are true, but reason is not the correct explanation of assertion.

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