Correct order of polarising power is

Options

A. `Cs^(+)ltK^(+)ltMg^(2+)ltAl^(3+)`
B. `K^(+)ltCs^(+)ltMg^(2+)ltAl^(3+)`
C. `Cs^(+)ltK^(+)ltAl^(3+)ltMg^(2+)`
D. `K^(+)ltCs^(+)ltAl^(3+)ltMg^(2+)`

Answer

To determine the correct order of polarizing power among the given cations (K⁺, Mg²⁺, Al³⁺), we need to consider two main factors that influence polarizing power:

1. **Charge of the Cation**: The greater the charge on the cation, the higher its polarizing power. This is because a higher charge leads to a stronger electric field, which can distort the electron cloud of nearby anions.

2. **Size of the Cation**: The smaller the size of the cation, the higher its polarizing power. A smaller cation can get closer to the anion, exerting a stronger pull on its electron cloud.

### Step-by-Step Solution:

1. **Identify the Cations and Their Charges**:
- K⁺ (Potassium ion) - Charge: +1
- Mg²⁺ (Magnesium ion) - Charge: +2
- Al³⁺ (Aluminum ion) - Charge: +3

2. **Analyze the Charges**:
- The charges on the cations increase from K⁺ (+1) to Mg²⁺ (+2) to Al³⁺ (+3).
- Higher charge generally results in higher polarizing power.

3. **Consider the Sizes of the Cations**:
- K⁺ is larger than Mg²⁺, which is larger than Al³⁺.
- Therefore, Al³⁺ is the smallest cation among the three, followed by Mg²⁺, and then K⁺.

4. **Combine the Effects of Charge and Size**:
- Al³⁺ has the highest charge (+3) and is the smallest, giving it the highest polarizing power.
- Mg²⁺ has a charge of +2 and is larger than Al³⁺, so its polarizing power is less than that of Al³⁺ but more than K⁺.
- K⁺ has the lowest charge (+1) and is the largest, giving it the lowest polarizing power.

5. **Establish the Order of Polarizing Power**:
- Based on the analysis, the order of polarizing power from highest to lowest is:
- Al³⁺ > Mg²⁺ > K⁺

### Final Answer:
The correct order of polarizing power is: **Al³⁺ > Mg²⁺ > K⁺**