Assertion (A) Beryllium and aluminium show diagonal relationship.
Reason (R )This is due to exactly same charge /radius ratio.

Options

A. Both Assertion and reason are correct and Reason is the correct explanation of the Assertion
B. Both assertion and Reason are correct but Reason is not the correct explanation of Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are Incorrect

Answer

To solve the assertion and reason question regarding the diagonal relationship between beryllium and aluminium, we will analyze both statements step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Beryllium and Aluminium show diagonal relationship."
- **Explanation**: Beryllium (Be) is in Group 2, while Aluminium (Al) is in Group 13 of the periodic table. Elements that are diagonally positioned in the periodic table often exhibit similar properties due to their comparable size and charge characteristics. Therefore, this assertion is **correct**.

2. **Understanding the Reason (R)**:
- The reason states that "This is due to exactly same charge/radius ratio."
- **Explanation**: The diagonal relationship is often attributed to similarities in charge-to-radius ratios, but it is important to note that the charge-to-radius ratio for beryllium and aluminium is not exactly the same; it is nearly the same. Thus, this statement is **incorrect**.

3. **Conclusion**:
- Since the assertion is correct and the reason is incorrect, we can conclude that the correct option is that the assertion is true, but the reason is false.

### Final Answer:
- The correct answer is: **Assertion is correct but Reason is incorrect**.

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