In which of the following cases the covalent character and the mpt order are same :-

Options

A. `BeCl_(2), CaCl_(2), BaCl_(2)`
B. `NaCl, MgCl_(2), AlCl_(3)`
C. `BeO, MgO, CaO`
D. `NaF, MgF_(2), AlF_(3)`

Explanation

To solve the question regarding the covalent character and melting point (m.p.) order of different compounds, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Covalent Character and Melting Point**:
- Covalent character in ionic compounds increases with the decrease in the size of the cation and the increase in the charge of the cation.
- Melting point generally increases with the ionic character of the compound. Ionic character increases with the size of the cation and the charge.

2. **Analyzing Each Option**:
- **Option A: BeCl2, CaCl2, MgCl2**:
- These compounds are from the same group (Group 2).
- Covalent character decreases as the size of the cation increases: BeCl2 > MgCl2 > CaCl2.
- Melting point order (ionic character): CaCl2 > MgCl2 > BeCl2.
- **Conclusion**: Orders are opposite.

- **Option B: NaCl, MgCl2, AlCl3**:
- These compounds are from the same period (Period 3).
- Covalent character order: AlCl3 > MgCl2 > NaCl (due to smaller cation size).
- Melting point order (ionic character): NaCl < MgCl2 < AlCl3.
- **Conclusion**: Orders are opposite.

- **Option C: BeO, MgO, CaO**:
- These compounds are also from the same group (Group 2).
- Covalent character order: BeO > MgO > CaO.
- Melting point order: CaO > MgO > BeO.
- **Conclusion**: Orders are opposite.

- **Option D: NaF, MgF2, AlF3**:
- These compounds are from the same period (Period 3).
- Covalent character order: AlF3 > MgF2 > NaF (due to smaller cation size).
- Melting point order: AlF3 > MgF2 > NaF (due to higher lattice enthalpy).
- **Conclusion**: Orders are the same.

3. **Final Answer**:
- The only option where the covalent character and melting point order are the same is **Option D: NaF, MgF2, AlF3**.