Question

Among \(\mathrm{NaP}, \mathrm{NaCl}, \mathrm{NaBr}\) and \(\mathrm{Nal}\), the \(\mathrm{NaF}\) has highest melting point because (1) It has maximum ionic character. (2) It has minimum ionic character. (3) It has associated molecules. (4) It has least molecular weight.

Short answer

NaF has the highest melting point because it has maximum ionic character.

Step-by-step solution

- Understand the Melting Point

The melting point of a substance depends on the strength of forces holding its molecules together. For ionic compounds, ionic bonding strength is crucial.

- Review Ionic Character

Ionic character refers to how strongly the ions in a compound attract each other. The compound with the highest ionic character will have stronger attraction between ions, leading to a higher melting point.

- Compare Ionic Characters

Among \(\text{NaF}\), \(\text{NaCl}\), \(\text{NaBr}\), and \(\text{NaI}\), consider the relative ionic characters. Smaller ions with higher charges have stronger attractions.

- Analyze Sodium Halides

Fluorine is smaller and more electronegative than chlorine, bromine, and iodine. This makes \(\text{NaF}\) more ionic than \(\text{NaCl}\), \(\text{NaBr}\), and \(\text{NaI}\).

- Choose the Correct Answer

Given the high ionic character leads to a higher melting point, \(\text{NaF}\) has the highest melting point because its ionic character is the greatest. Therefore, the correct answer is (1) It has maximum ionic character.

Key concepts

Ionic Character

Ionic character describes how strongly the ions in a compound attract and hold onto each other. It depends largely on the difference in electronegativity between the two atoms forming the bond. The greater the difference in electronegativity, the more ionic character the bond has. In sodium halides like NaF, NaCl, NaBr, and NaI, this concept is key to understanding their properties.

Fluorine is the most electronegative element and forms very strong ionic bonds with sodium. This makes NaF the compound with the highest ionic character among the sodium halides. As a result, the bonds in NaF are very strong, leading to a high melting point.

When comparing ionic character, it's important to look at both the size of the ions and their charges. Generally, smaller ions with higher charges will have stronger attractions and thus higher ionic character.

Melting Point

The melting point of a substance is the temperature at which it transitions from a solid to a liquid. For ionic compounds, this depends on the strength of the ionic bonds holding the ions together. Stronger bonds require more energy to break, resulting in a higher melting point.

In the case of sodium halides, NaF has the highest melting point because of its strong ionic bonds. The small size of the fluoride ion and the high electronegativity of fluorine contribute to these strong bonds. Thus, more energy (higher temperature) is needed to break these bonds and melt the compound.

This concept emphasizes the linkage between ionic character and melting point: the greater the ionic character, the higher the melting point.

Ionic Bonding Strength

Ionic bonding strength is a crucial factor in determining the physical properties of ionic compounds, such as their melting points. It is influenced by the size of the ions and their charge. Smaller ions with higher charges will generally form stronger bonds.

In sodium halides, the strength of the ionic bond decreases as we move from fluorine to iodine in the halide group. NaF has the strongest ionic bond because fluoride ions are small and highly electronegative. This results in a high degree of electrostatic attraction between the sodium and fluoride ions.

The stronger the ionic bonding in a compound, the higher the energy required to break these bonds during melting. This explains why NaF, with its strong ionic bonds, has a much higher melting point than NaCl, NaBr, and NaI. Ionic bonding strength is therefore a critical factor in understanding the melting points of various sodium halides.