In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cation–anion distances are 2.01 Å (Li–F), 2.82 Å (Na–Cl), 3.30 Å (K–Br), and 3.67 Å (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?

Verified step by step guidance

1. Identify the bonding atomic radii for each of the cations (Li, Na, K, Rb) and anions (F, Cl, Br, I) from a reliable source such as a chemistry textbook or database.
2. Calculate the estimated cation–anion distance for each compound by adding the bonding atomic radius of the cation to that of the anion. For example, for LiF, add the bonding atomic radius of Li to that of F.
3. Compare the calculated distances using bonding atomic radii to the measured distances provided in the problem statement.
4. Discuss the accuracy of these estimates by considering the nature of bonding atomic radii, which are based on neutral atoms, versus ionic radii, which account for the ionic nature and charge of the atoms in the compound.
5. Conclude whether the estimates using bonding atomic radii are as accurate as those using ionic radii, considering the differences in atomic and ionic sizes due to electron transfer in ionic compounds.

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 influences the properties of the compound, including its melting point, solubility, and the distances between ions in the crystal lattice. Understanding the nature of ionic bonding is essential for analyzing cation-anion distances.

Bonding Atomic Radii

Bonding atomic radii refer to the effective size of an atom when it forms a bond with another atom. These radii are typically derived from the distances between nuclei in bonded atoms and can vary depending on the type of bond (ionic or covalent). Using bonding atomic radii to estimate cation-anion distances provides a different perspective compared to using ionic radii, which are based on the size of isolated ions.

Ionic Radii

Ionic radii are measurements that represent the size of an ion in a crystal lattice. They vary based on the ion's charge and coordination number, with cations generally being smaller than their neutral atoms and anions being larger. When estimating cation-anion distances, ionic radii provide a more accurate representation of the actual distances in ionic compounds compared to neutral atomic radii, which do not account for the charge interactions.