Chapter 12, Problem 25A

Interpretation Introduction

Interpretation:

The structure of ionic solids is to be described in general terms.

Concept introduction:

Ionic solids are the solids made up of ions. They are made generally when metal and non-metal combines with each other.

Answer to Problem 25A

Ionic solid contains specific number of positive and negative charged ions. It is represented as simple whole number formula called empirical formula. Ions are arranged in crystal lattice so that attraction between the ions is maximum and repulsions are minimum.

Explanation of Solution

One unit of Crystal lattice of $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ has $6\mathrm{N}{\mathrm{a}}^{+}\mathrm{a}\mathrm{n}\mathrm{d}6\mathrm{C}{\mathrm{l}}^{-}$ . It is arranged in face centred cubic lattice. Each sodium ion is surrounded by six chloride ions and six sodium ions are surrounded by each chloride ion. Therefore, $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ is the empirical formula of sodium chloride crystal.

Conclusion

Thus, ionic solids are arranged in specific pattern which is repeated in a whole crystal. The repeating unit is called unit cell. The formula of unit cell is the actual formula of ionic compound.