Which of the following halides has the highest meting point ?

Options

A. NaCl
B. NaBr
C. NaF
D. Nal

Answer

To determine which of the given sodium halides has the highest melting point, we will analyze the ionic nature of the compounds based on the size of the anions involved. The sodium halides provided are NaCl, NaBr, NaF, and NaI.

### Step-by-Step Solution:

1. **Identify the Compounds**: The sodium halides in question are:
- NaCl (Sodium Chloride)
- NaBr (Sodium Bromide)
- NaF (Sodium Fluoride)
- NaI (Sodium Iodide)

2. **Understand Ionic Compounds**: Ionic compounds generally have high melting points due to the strong electrostatic forces between the positively charged cations and negatively charged anions.

3. **Analyze the Cation**: In all the compounds listed, the cation is the same: Na⁺ (Sodium ion).

4. **Examine the Anions**: The anions differ in size:
- F⁻ (Fluoride)
- Cl⁻ (Chloride)
- Br⁻ (Bromide)
- I⁻ (Iodide)

5. **Consider Anion Size**: As we move down the group in the periodic table, the size of the halide anions increases:
- F⁻ < Cl⁻ < Br⁻ < I⁻

6. **Evaluate Ionic Character**: The ionic character of a compound is influenced by the size of the cation and anion. A smaller anion leads to a more ionic character. Therefore, the order of ionic character based on the anion size is:
- NaF (F⁻ is the smallest) > NaCl > NaBr > NaI (I⁻ is the largest)

7. **Determine Melting Points**: Since NaF has the highest ionic character due to the small size of F⁻, it will have the highest melting point among the sodium halides.

8. **Conclusion**: The sodium halide with the highest melting point is NaF.

### Final Answer:
**NaF (Sodium Fluoride) has the highest melting point among the given halides.**

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