Of the following diagrams, which best represents the structure of solid KF? [VISUAL] — Bonding Chemistry Question

STEPS:

1. Identify the substance and its chemical bonding:
Potassium fluoride ($\text{KF}$) is composed of potassium ($\text{K}$), an alkali metal, and fluorine ($\text{F}$), a halogen. Because it consists of a metal bonded to a highly electronegative nonmetal, $\text{KF}$ is an ionic compound made of $\text{K}^+$ cations and $\text{F}^-$ anions.

2. Recall the physical structure of ionic solids:
In the solid state, ionic compounds do not form individual, isolated molecules. Instead, they assemble into a highly ordered, three-dimensional crystalline lattice.

3. Apply the principles of electrostatic forces (Coulomb's Law):
The stability of an ionic lattice is governed by Coulombic attractions and repulsions:
* Attractive forces occur between oppositely charged ions ($\text{K}^+$ and $\text{F}^-$).
* Repulsive forces occur between like-charged ions ($\text{K}^+$ with $\text{K}^+$, and $\text{F}^-$ with $\text{F}^-$).
* To maximize attractive forces and minimize repulsive forces, an ionic solid must pack its ions so that each ion is directly surrounded by ions of the opposite charge. This structural arrangement represents the lowest potential energy state attainable by the constituent ions.

4. Identify the diagram that matches this stable configuration:
* Option B represents a tightly packed, highly ordered crystalline structure where every positive cation is directly surrounded by negative anions, and vice versa. This correctly depicts the stable lattice of solid $\text{KF}$, making Option B the correct answer.

*

WHY_OTHERS_WRONG:

• Option A is incorrect: This diagram represents a structure where layers are made of alternating pairs of ions of the *same charge*. Placing like-charged ions directly adjacent to one another generates massive electrostatic repulsions, making this configuration highly unstable and physically impossible for an ionic solid.
• Option C is incorrect: This diagram shows alternating layers consisting entirely of ions of the *same charge*. The alignment of complete sheets of identical charges next to one another would create extreme repulsive forces, preventing the formation of a stable crystalline solid.
• Option D is incorrect: This diagram represents widely separated and randomly dispersed ions. This high-entropy particulate arrangement is characteristic of a substance in the gas phase, not solid $\text{KF}$.