Which of the following halides has the highest melting point-

Options

A. (a) NaCl
B. (b) NaBr
C. (c) NaF
D. (d) Nal

Answer

To determine which of the given sodium halides has the highest melting point, we can follow these steps:

### Step 1: Identify the Halides
The halides provided are:
- NaCl (Sodium Chloride)
- NaBr (Sodium Bromide)
- NaF (Sodium Fluoride)
- NaI (Sodium Iodide)

### Step 2: Understand the Nature of the Compounds
All these compounds are ionic in nature since they are formed from sodium (an alkali metal) and halide ions.

### Step 3: Determine the Factors Affecting Melting Point
The melting point of ionic compounds is influenced by the electrostatic force of attraction between the oppositely charged ions. Generally, the stronger the force of attraction, the higher the melting point.

### Step 4: Analyze the Size of the Halide Ions
The size of the halide ions increases as we move down the group in the periodic table. The order of ionic size for the halides is:
- Fluoride ion (F⁻) < Chloride ion (Cl⁻) < Bromide ion (Br⁻) < Iodide ion (I⁻)

### Step 5: Relate Ionic Size to Melting Point
Since the electrostatic force of attraction is inversely proportional to the size of the ions, smaller ions will have stronger attractions and thus higher melting points.

### Step 6: Compare the Halides
- NaF has the smallest halide ion (F⁻), leading to the strongest electrostatic attraction and the highest melting point.
- NaCl has a larger halide ion (Cl⁻) than NaF, so it has a lower melting point than NaF.
- NaBr has an even larger halide ion (Br⁻) than NaCl, resulting in an even lower melting point.
- NaI has the largest halide ion (I⁻), leading to the weakest attraction and the lowest melting point.

### Step 7: Conclusion
Based on the analysis, the order of melting points from highest to lowest is:
- NaF > NaCl > NaBr > NaI

Thus, the halide with the highest melting point is **NaF**.

### Final Answer
The halide with the highest melting point is **NaF (Option C)**.

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