Compare and contrast the structures of the following solids. a. \(\mathrm{CO}_{2}(s)\) versus \(\mathrm{H}_{2} \mathrm{O}(s)\) b. \(\mathrm{NaCl}(s)\) versus \(\mathrm{CsCl}(s)\) ; see Exercise 71 for the structures.

First, we will identify the type of bonding present in each compound. This will help us understand their crystal structures more effectively. a. \(\mathrm{CO}_{2}(s)\): Carbon dioxide has covalent bonding between the carbon and oxygen atoms, forming a linear molecule. \(\mathrm{H}_{2} \mathrm{O}(s)\): Water has covalent bonding between the oxygen and hydrogen atoms, forming a bent molecule due to the presence of two lone pairs on the oxygen atom. b. \(\mathrm{NaCl}(s)\): Sodium chloride consists of ionic bonding between positively charged sodium ions (\(\mathrm{Na}^+\)) and negatively charged chloride ions (\(\mathrm{Cl}^-\)). \(\mathrm{CsCl}(s)\): Cesium chloride also consists of ionic bonding, between positively charged cesium ions (\(\mathrm{Cs}^+\)) and negatively charged chloride ions (\(\mathrm{Cl}^-\)).

Now that we know the bonding types present in these compounds, we can discuss their crystal structures in more detail. a. \(\mathrm{CO}_{2}(s)\): Solid carbon dioxide, also known as dry ice, has a molecular solid structure held together by weak van der Waals forces. The repeating structural unit is a single \(\mathrm{CO}_2\) molecule. Due to the weak intermolecular forces, dry ice sublimes directly into gas at low pressures, without passing through a liquid phase. \(\mathrm{H}_{2} \mathrm{O}(s)\): Solid water, or ice, forms a hexagonal lattice structure held together by strong hydrogen bonding between adjacent water molecules. This lattice structure causes ice to be less dense than liquid water, resulting in ice floating on water. b. \(\mathrm{NaCl}(s)\): Sodium chloride forms a face-centered cubic (FCC) crystal structure, with alternating \(\mathrm{Na}^+\) and \(\mathrm{Cl}^-\) ions in a 1:1 ratio. Each ion is surrounded by six neighbors of the opposite charge, creating a three-dimensional lattice structure. \(\mathrm{CsCl}(s)\): Cesium chloride forms a simple cubic crystal structure, with one \(\mathrm{Cs}^+\) ion in the center and eight \(\mathrm{Cl}^-\) ions at the corners of the cubic unit cell. Each ion is surrounded by eight neighbors of the opposite charge, creating a 1:1 ratio in the three-dimensional lattice structure.

Finally, we will compare the structures within each pair. a. \(\mathrm{CO}_{2}(s)\) vs. \(\mathrm{H}_{2} \mathrm{O}(s)\): Both have covalent bonding within their respective molecules but differ in their crystal structures and intermolecular forces. Solid \(\mathrm{CO}_2\) has a molecular solid structure with weak van der Waals forces holding it together, while solid water has a hexagonal lattice structure with strong hydrogen bonding. This results in vastly differing physical properties, such as the lower density of ice compared to water and the sublimation of dry ice at low pressures. b. \(\mathrm{NaCl}(s)\) vs. \(\mathrm{CsCl}(s)\): Both structures have ionic bonding and a 1:1 ratio of cations and anions, but have different arrangements of their ions. Sodium chloride forms a face-centered cubic (FCC) crystal structure, while cesium chloride forms a simple cubic crystal structure. This difference in arrangement leads to variations in coordination numbers, with each ion in \(\mathrm{NaCl}\) being surrounded by six neighbors of the opposite charge, while in \(\mathrm{CsCl}\), each ion is surrounded by eight neighbors of the opposite charge.