Consider the ionic compounds KF, NaCl, NaBr, and LiCl. (a) Use ionic radii (Figure 7.8) to estimate the cation–anion distance for each compound.

Verified step by step guidance

1. Identify the cations and anions in each compound: KF (K^+ and F^-), NaCl (Na^+ and Cl^-), NaBr (Na^+ and Br^-), LiCl (Li^+ and Cl^-).
2. Refer to Figure 7.8 or a reliable source to find the ionic radii for each ion: K^+, Na^+, Li^+, F^-, Cl^-, and Br^-.
3. For each compound, add the ionic radius of the cation to the ionic radius of the anion to estimate the cation–anion distance.
4. Express the cation–anion distance in appropriate units, typically in picometers (pm) or angstroms (Å).
5. Compare the estimated distances to understand how ionic size affects the structure of these compounds.

Key Concepts

Ionic Radius

Ionic radius refers to the size of an ion in a crystal lattice. Cations (positively charged ions) are typically smaller than their neutral atoms due to the loss of electrons, while anions (negatively charged ions) are larger due to the gain of electrons. Understanding ionic radii is crucial for estimating the distances between cations and anions in ionic compounds.

Cation-Anion Distance

The cation-anion distance is the distance between the centers of a cation and an anion in an ionic compound. This distance can be estimated by adding the ionic radii of the respective cation and anion. Accurate estimation of this distance is important for understanding the properties of ionic compounds, such as lattice energy and stability.

Lattice Energy

Lattice energy is the energy released when gaseous ions combine to form an ionic solid. It is influenced by the charges of the ions and the distance between them, as described by Coulomb's law. A greater cation-anion distance typically results in lower lattice energy, affecting the compound's melting point and solubility.