Assertion: Li and Mg shows similar chemical properties.
Reason Li and Mg belongs to `2^(nd)` period.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False
D. If both Assertion & Reason are False

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Li and Mg show similar chemical properties."
- We need to determine if this statement is true or false.

2. **Analyzing Lithium (Li) and Magnesium (Mg)**:
- Lithium (Li) is an alkali metal located in Group 1 of the periodic table.
- Magnesium (Mg) is an alkaline earth metal located in Group 2 of the periodic table.
- Despite being in different groups, Li and Mg are known to exhibit some similar chemical properties.

3. **Reason for Similar Properties**:
- The reason given is that "Li and Mg belong to the 2nd period."
- However, upon checking, we find that Lithium is indeed in the 2nd period, but Magnesium is in the 3rd period. Therefore, this reason is incorrect.

4. **Similar Properties of Li and Mg**:
- Both Li and Mg form soluble chlorides (LiCl and MgCl2) in ethanol.
- Both hydroxides (LiOH and Mg(OH)2) are weak bases.
- The similarity in their chemical properties can be attributed to their similar ionic sizes and diagonal relationship in the periodic table.

5. **Conclusion**:
- The assertion that Li and Mg show similar chemical properties is true.
- The reason that they belong to the same period is false.
- Therefore, the correct answer is that the assertion is true but the reason is false.

### Final Answer:
The correct option is: "Assertion is true but the reason is false."

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