Assertion: `Li` resembles with `Mg` in properties
Reason: `Li^(+)` has almost same polarising power as `Mg^(2+)`.

Options

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

Answer

To solve the question regarding the assertion and reason provided, we can break it down into a step-by-step analysis:

### Step 1: Understand the Assertion
The assertion states that "Li resembles with Mg in properties."
- **Explanation**: Lithium (Li) and Magnesium (Mg) are both elements found in the periodic table, with Li being an alkali metal (Group 1) and Mg being an alkaline earth metal (Group 2). They are diagonally related in the periodic table, which often leads to similarities in their chemical and physical properties.

**Hint**: Look into the periodic table to understand the position of Li and Mg and their group classifications.

### Step 2: Understand the Reason
The reason states that "Li^(+) has almost the same polarizing power as Mg^(2+)."
- **Explanation**: Polarizing power refers to the ability of a cation to distort the electron cloud of an anion. The polarizing power is influenced by the charge and size of the cation. Li^(+) has a +1 charge and a relatively small size, while Mg^(2+) has a +2 charge and is also small but has a higher charge density. This means that both ions can polarize anions similarly due to their comparable sizes and charge densities.

**Hint**: Consider the definitions of polarizing power and how it relates to ionic size and charge.

### Step 3: Analyze the Relationship
Now, we need to analyze the relationship between the assertion and the reason.
- **Explanation**: The reason given explains why the assertion is true. Since both Li and Mg have similar atomic radii and electron densities, their polarizing powers are comparable. This similarity in polarizing power contributes to the resemblance in properties between Li and Mg.

**Hint**: Think about how the properties of elements can be influenced by their ionic characteristics.

### Step 4: Conclusion
Based on the analysis:
- Both the assertion and the reason are true.
- The reason correctly explains the assertion.

Thus, we conclude that the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

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