Which of the following order is incorrect :-

Options

A. Ionic character= `MCl lt MCl_(2) lt MCl_(3)`
B. Polarizibility `= F lt Cl^(-) lt Br^(-) lt I^(-)`
C. Polarising power `=Na^(+) lt C^(+2) lt Mg^(+2) lt Al^(+3)`
D. Covalent character`=LiF lt LiCl lt LiBr lt LiI`

Answer

To determine which of the given orders is incorrect, we will analyze the options based on Fajans' rules, which relate to the polarizing power of cations and the polarizability of anions.

### Step-by-Step Solution:

1. **Understand Fajans' Rule**:
- Fajans' rule states that the covalent character of an ionic bond increases with the increase in the charge of the cation and the size of the anion.
- A small cation has a higher polarizing power, while a large anion has higher polarizability.

2. **Analyze the Given Orders**:
- We need to check each order provided in the options to see if they align with Fajans' rule.

3. **Order 1: M⁺, M²⁺, M³⁺**:
- As the charge on the cation increases (from M⁺ to M³⁺), the covalent character increases, and thus the ionic character decreases.
- This order is **correct** as per Fajans' rule.

4. **Order 2: Anions Size**:
- If the order involves anions like F⁻, Cl⁻, Br⁻, I⁻, the polarizability increases with the size of the anion.
- This order is also **correct**.

5. **Order 3: Polarizing Power**:
- The polarizing power of cations increases with the charge and decreases with size.
- If the order states that a higher charge cation has more polarizing power, this is also **correct**.

6. **Order 4: Covalent Character**:
- The order of covalent character among anions (F⁻, Cl⁻, Br⁻, I⁻) should follow the trend of increasing size leading to increasing covalent character.
- This order is also **correct**.

7. **Conclusion**:
- After analyzing all the options, we find that all provided orders are correct based on Fajans' rules. Hence, if the question asks for the incorrect order, we conclude that the first order (M⁺, M²⁺, M³⁺) is indeed **the only one that is incorrectly stated** in the context of the question.