Which is / are true statement(s) ?

Options

A. Basic nature of `X^(-)` is in order `F^(-) gt Cl^(-) gt Br^(-) gt l^(-)`
B. Hl is strongest acid of HF, HCl, HBr and HI
C. The ionic character of M-X bond decreases in the order `M-F gt M-Cl gt M-Br lt M gt l`
D. Among F, Cl, Br and I, F has the highest enthalpy of hydration.

Answer

To determine which statements are true regarding the properties of halogens and their compounds, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A: The basic nature of X⁻ ion in order is F⁻ < Cl⁻ < Br⁻ < I⁻.**
- **Analysis:** As we move down the group in the periodic table, the size of the anions increases. Larger anions tend to be more basic because they can better stabilize the negative charge. Therefore, the correct order of basicity should be I⁻ > Br⁻ > Cl⁻ > F⁻.
- **Conclusion:** This statement is **incorrect**.

2. **Statement B: HI is the strongest acid among HF, HCl, HBr, and HI.**
- **Analysis:** As we move down the group from HF to HI, the bond strength decreases due to the increasing size of the halogen atom. HI has the weakest bond among these acids, making it easier to donate a proton (H⁺). Therefore, HI is indeed the strongest acid in this group.
- **Conclusion:** This statement is **correct**.

3. **Statement C: The ionic character of the MX bond decreases in order MF, MCl, MBr, and MI.**
- **Analysis:** The ionic character of a bond is influenced by the size of the atoms involved. As the size of the halogen increases from F to I, the bond becomes more covalent due to decreased electronegativity differences and increased atomic size. Therefore, the order of ionic character is indeed MF > MCl > MBr > MI.
- **Conclusion:** This statement is **correct**.

4. **Statement D: Among fluorine, chlorine, bromine, and iodine, fluorine has the highest enthalpy of hydration.**
- **Analysis:** The enthalpy of hydration is related to the size and charge density of the ion. Smaller ions typically have higher hydration enthalpy due to their higher charge density. However, while fluorine is small, the enthalpy of hydration is actually highest for I⁻ due to the larger size and better solvation in water. Thus, this statement is incorrect.
- **Conclusion:** This statement is **incorrect**.

### Final Conclusion:
The correct statements are **B and C**.