Solubility Order of Sodium Halides

The solubility order of sodium halides can be determined by considering the nature of the halide ions and their interaction with water molecules. The solubility of a compound is influenced by factors such as the polarity and size of the ions, as well as the strength of the ion-dipole interactions between the ions and water molecules.

1. Sodium Fluoride (NaF)
- Sodium fluoride (NaF) is highly soluble in water.
- This is due to the small size of fluoride ions (F-) and their high charge density, allowing them to form strong ion-dipole interactions with water molecules.
- The polar water molecules surround and stabilize the fluoride ions, leading to the dissolution of NaF.

2. Sodium Chloride (NaCl)
- Sodium chloride (NaCl) is also highly soluble in water.
- The chloride ions (Cl-) are larger than fluoride ions but still small enough to form strong ion-dipole interactions with water.
- The polar water molecules surround and stabilize the chloride ions, resulting in the dissolution of NaCl.

3. Sodium Bromide (NaBr)
- Sodium bromide (NaBr) is moderately soluble in water.
- Bromide ions (Br-) are larger than chloride ions and have a lower charge density, which reduces the strength of the ion-dipole interactions with water.
- While some NaBr will dissolve in water, it is less soluble compared to NaF and NaCl.

4. Sodium Iodide (NaI)
- Sodium iodide (NaI) is the least soluble among the sodium halides.
- Iodide ions (I-) are larger than bromide ions and have an even lower charge density, resulting in weaker ion-dipole interactions with water.
- Due to these weaker interactions, NaI has a lower solubility compared to NaF, NaCl, and NaBr.

Summary:
The solubility order of sodium halides, from highest to lowest, is NaF > NaCl > NaBr > NaI. This order is primarily determined by the size and charge density of the halide ions, as well as the strength of the ion-dipole interactions with water molecules. Sodium fluoride and sodium chloride are highly soluble due to their small size and high charge density, while sodium bromide is moderately soluble, and sodium iodide is the least soluble among the sodium halides.