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Ch.7 - Periodic Properties of the Elements
Chapter 7, Problem 36b

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. b. Calculate the difference between the experimentally measured ion–ion distances and the ones predicted from Figure 7.8.

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Identify the experimentally measured cation–anion distances for each ionic compound: LiF (2.01 Å), NaCl (2.82 Å), KBr (3.30 Å), and RbI (3.67 Å).
Refer to Figure 7.8 to find the predicted ion–ion distances for each of the ionic compounds based on the ionic radii of the cations and anions involved.
Subtract the predicted ion–ion distance from the experimentally measured distance for each compound to find the difference.
Express the differences in distances for each compound in Ångströms (Å).
Review the differences to understand any trends or discrepancies between the experimental and predicted values.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Bonding

Ionic bonding occurs when atoms transfer electrons, resulting in the formation of charged ions. Cations (positively charged) and anions (negatively charged) attract each other due to electrostatic forces, creating ionic compounds. Understanding this concept is crucial for analyzing the properties and distances between ions in compounds like LiF, NaCl, KBr, and RbI.
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Cation-Anion Distances

Cation-anion distances refer to the measured distances between the centers of cations and anions in an ionic compound. These distances can be influenced by factors such as ionic size, charge, and the lattice structure of the compound. Analyzing these distances helps in understanding the stability and strength of ionic bonds in different compounds.
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Experimental vs. Predicted Values

In chemistry, comparing experimental measurements with predicted values allows for the validation of theoretical models. In this context, the experimentally measured ion-ion distances can be compared to those predicted from established models or figures, such as Figure 7.8. This comparison helps identify discrepancies that may arise from factors like ionic radii or lattice energy.
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