In the ionic compounds LiF, NaCl, KBr, and RbI, the measured c...

Question

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

Accepted Answer

Step 1: To estimate the cation-anion distance using neutral atom bonding atomic radii, you need to know the atomic radii of the neutral atoms. You can find these values in a periodic table that includes atomic radii. The atomic radius is half the distance between the nuclei of two atoms of the same element when the atoms are joined.. Step 2: Once you have the atomic radii, add the radius of the cation (the positively charged ion) to the radius of the anion (the negatively charged ion) to estimate the cation-anion distance. For example, for LiF, you would add the atomic radius of Li to the atomic radius of F.. Step 3: Repeat this process for each of the four compounds: LiF, NaCl, KBr, and RbI.. Step 4: Compare these estimated distances to the measured cation-anion distances given in the problem. This will give you an idea of how accurate your estimates are.. Step 5: In general, estimates using ionic radii are more accurate than those using neutral atom bonding atomic radii. This is because ionic radii take into account the changes in atomic size that occur when atoms gain or lose electrons to form ions. In contrast, neutral atom bonding atomic radii are based on the sizes of neutral atoms, which do not account for these changes.

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Key Concepts

Ionic Compounds

Atomic Radii

Cation-Anion Distance