Conduction of an electric current is a general property associated with metals. How does the band theory for metallic bonding explain conductivity?

Considering only the molecular orbitals formed by combinations of the 2s atomic orbitals, how many molecular orbitals can be formed by 1000 Li atoms? In the lowest energy state, how many of these orbitals will be populated by pairs of electrons and how many will be empty?

When a graphene sheet has a width of 1.0 micrometer, how many ${C}_6$ rings are joined across the sheet?

Determine the lattice enthalpy for RbCl. You will need the following information:

$$\begin{gathered} \Delta_f H^{\circ}[{Rb}({g})]=80.9 {~kJ} / {mol} \\ \Delta_f H^{\circ}[{RbCl}({s})]=-435.4 {~kJ} / {mol} \end{gathered}$$

Determine the molar enthalpy of formation, $\Delta_f H^{\circ}$, of solid lithium fluoride from the lattice energy (table below) and other thermochemical data. The enthalpy of formation of ${Li}({g}), \Delta_f H^{\circ}[{Li}({g})]=$ 159.37 kJ/mol. Other required data can be found in Appendices F and L.

Lattice Energies of Some Ionic Compounds

$$\begin{array}{l|r} \hline \text { Compound } & \begin{array}{r} \Delta_{\text {lattice }} U \\ (\mathrm{~kJ} / \mathrm{mol}) \end{array} \\ \hline \mathrm{LiF} & -1037 \\ \hline \mathrm{LiCl} & -852 \\ \hline \mathrm{LiBr} & -815 \\ \hline \mathrm{Lil} & -761 \\ \hline \mathrm{NaF} & -926 \\ \hline \mathrm{NaCl} & -786 \\ \hline \mathrm{NaBr} & -752 \\ \hline \mathrm{Nal} & -702 \\ \hline \mathrm{KF} & -821 \\ \hline \mathrm{KCl} & -717 \\ \mathrm{KBr} & -689 \\ \mathrm{KI} & -649 \\ \hline \end{array}$$

Which compound in each of the following pairs should have the higher melting point? Explain briefly.

(a) NaCl or RbCl

(b) BaO or MgO

(c) NaCl or MgS

To melt an ionic solid, energy must be supplied to disrupt the forces between ions so the regular array of ions collapses. Predict (and explain) how the melting point is expected to vary as a function of the distance between cation and anion.

Examine the trends in lattice energy in the table below. The value of the lattice energy becomes somewhat more negative on going from NaI to NaBr to NaCl, and all are in the range from -700 to -800 kJ/mol. Propose a reason for the observation that the lattice energy of ${NaF}\left(\Delta_{\text {lattice }} U=-926 {~kJ} / {mol}\right)$ is much more negative than those of the other sodium halides.

Lattice Energies of Some Ionic Compounds

$$\begin{array}{l|r} \hline \text { Compound } & \begin{array}{r} \Delta_{\text {lattice }} U \\ (\mathrm{~kJ} / \mathrm{mol}) \end{array} \\ \hline \mathrm{LiF} & -1037 \\ \hline \mathrm{LiCl} & -852 \\ \hline \mathrm{LiBr} & -815 \\ \hline \mathrm{Lil} & -761 \\ \hline \mathrm{NaF} & -926 \\ \hline \mathrm{NaCl} & -786 \\ \hline \mathrm{NaBr} & -752 \\ \hline \mathrm{Nal} & -702 \\ \hline \mathrm{KF} & -821 \\ \hline \mathrm{KCl} & -717 \\ \mathrm{KBr} & -689 \\ \mathrm{KI} & -649 \\ \hline \end{array}$$

Predict the trend in lattice energy, from least negative to most negative, for the following compounds based on the ion charges and ionic radii: LiI, LiF, CaO, RbI.

A unit cell of cesium chloride is illustrated in Figure 12.8. The density of the solid is 3.99 g/cm$^3$, and the radius of the Cl$^−$ ion is 181 pm. Calculate the radius of the Cs$^+$ ion in the center of the cell. (Assume that the Cs$^+$ ion touches all of the corner Cl$^−$ ions.)

Based on a C-C distance of 139 pm, determine the side-to-side dimension of a planar, ${C}_6$ ring.

Determine how many tin atoms are contained in the tetragonal crystal lattice unit cell of $\beta$-tin. How many tin atoms are contained in the cubic crystal lattice unit cell of $\alpha$-tin?

What mass of lithium can be acquired from 73 million metric tons of lithium carbonate? (1 metric ton = 1000 kg.)

According to the Eysencks’ theory, people who score high on neuroticism tend to be ________.
a. calm
b. stable
c. outgoing
d. anxious