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 order is incorrect among the given options, we need to analyze the concepts of ionic character, polarizability, polarizing power, and covalent character. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Ionic Character
Ionic character refers to the extent to which a bond between two atoms has ionic characteristics. Generally, the ionic character increases with the difference in electronegativity between the two atoms involved in the bond.

### Step 2: Analyze Polarizability
Polarizability is the ability of an ion to be distorted by an electric field. Larger ions with more electrons are generally more polarizable. The order given is:
- F⁻ < Cl⁻ < Br⁻ < I⁻
This order is correct because as we move down the group in the periodic table, the size of the ions increases, leading to higher polarizability.

### Step 3: Analyze Polarizing Power
Polarizing power is the ability of a cation to distort the electron cloud of an anion. It is influenced by the charge and size of the cation. The order given is:
- Na⁺ < Ca²⁺ < Mg²⁺ < Al³⁺
To compare these, we consider charge density (charge/size). Smaller cations with higher charges have greater polarizing power.

### Step 4: Evaluate the Polarizing Power Order
- Na⁺ has a lower charge density than Ca²⁺ because Na⁺ is larger than Ca²⁺.
- However, Na⁺ is less polarizing than Ca²⁺, which is incorrect since Na⁺ has a higher charge density due to its smaller size compared to Ca²⁺.

### Step 5: Check Covalent Character
Covalent character refers to the extent to which a bond has covalent characteristics. The order given is:
- LiF < LiCl < LiBr < LiI
This order is correct as the covalent character increases with the size of the anion, leading to greater distortion of the electron cloud.

### Conclusion
Based on the analysis, the incorrect order is the polarizing power order given as:
- Na⁺ < Ca²⁺
This is incorrect because Na⁺ should have a higher polarizing power than Ca²⁺ due to its higher charge density.

### Final Answer
The incorrect order is:
**Option 3: Polarizing power: Na⁺ < Ca²⁺**