In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cation–anion distances are 201 pm (Li–F), 282 pm (Na–Cl), 330 pm (K–Br), and 367 pm (Rb–I), respectively. (c) What estimates of the cation– anion distance would you obtain for these four compounds using neutral atom bonding atomic radii? Are these estimates as accurate as the estimates using ionic radii?

Key Concepts

Ionic Compounds

Ionic compounds are formed through the electrostatic attraction between positively charged cations and negatively charged anions. The strength of this attraction depends on the charges of the ions and the distance between them. Understanding the structure and properties of ionic compounds is essential for analyzing their cation-anion distances.

Atomic Radii

Atomic radii refer to the size of an atom, typically measured from the nucleus to the outer boundary of the surrounding cloud of electrons. In the context of ionic compounds, ionic radii are used to estimate the distance between cations and anions. However, neutral atom bonding atomic radii can also provide estimates, which may differ due to the nature of ionic versus covalent bonding.

Cation-Anion Distance

Cation-anion distance is the measure of the distance between the centers of a cation and an anion in an ionic compound. This distance can be influenced by the size of the ions and their charges. Comparing distances obtained from ionic radii versus neutral atomic radii helps assess the accuracy of different methods in estimating the structural parameters of ionic compounds.