Why does white phosphorus consist of tetrahedral $\mathrm{P}_4$ molecules while nitrogen consists of diatomic $\mathrm{N}_2$ molecules?

Determine the oxidation number of each element in each of the following compounds: (a) $\mathrm{HCN}$ (b) $\mathrm{OF}_2$ (c) $\mathrm{AsCl}_3$

Write balanced chemical equations for the reaction of the following acid anhydrides with water: (a) $\mathrm{SO}_3$ (b) $\mathrm{N}_2 \mathrm{O}_3$ (c) $\mathrm{Cl}_2 \mathrm{O}_7$ (d) $\mathrm{P}_4 \mathrm{O}_{10}$ (e) $\mathrm{NO}_2$

Nitrogen in the atmosphere exists as very stable diatomic molecules. Why does phosphorus form less stable $\mathrm{P}_4$ molecules instead of $\mathrm{P}_2$ molecules?

Carbon forms a number of allotropes, two of which are graphite and diamond. Silicon has a diamond structure. Why is there no allotrope of silicon with a graphite structure?

Suppose you discovered a diamond completely encased in a silicate rock. How would you chemically free the diamond without harming it?

A hydride of silicon prepared by the reaction of $\mathrm{Mg} 2 \mathrm{Si}$ with acid exerted a pressure of 306 torr at $26^{\circ} \mathrm{C}$ in a bulb with a volume of $57.0 \mathrm{~mL}$. If the mass of the hydride was $0.0861 \mathrm{~g}$, what is its molecular mass? What is the molecular formula for the hydride?

From the data given in Appendix I, determine the standard enthalpy change and the standard free energy change for each of the following reactions: (a) $\mathrm{BF}_3(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(l) \longrightarrow \mathrm{B}(\mathrm{OH})_3(\mathrm{~s})+3 \mathrm{HF}(\mathrm{g})$ (b) $\mathrm{BCl}_3(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(l) \longrightarrow \mathrm{B}(\mathrm{OH})_3(\mathrm{~s})+3 \mathrm{HCl}(\mathrm{g})$ (c) $\mathrm{B}_2 \mathrm{H}_6(\mathrm{~g})+6 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \longrightarrow 2 \mathrm{~B}(\mathrm{OH})_3(s)+6 \mathrm{H}_2(\mathrm{~g})$

Write a formula for each of the following compounds: (a) silicon dioxide (b) silicon tetraiodide (c) silane (d) silicon carbide (e) magnesium silicide

Predict the best choice in each of the following. You may wish to review the chapter on electronic structure for relevant examples. (a) the most metallic of the elements $\mathrm{Al}, \mathrm{Be}$, and $\mathrm{Ba}$ (b) the most covalent of the compounds $\mathrm{NaCl}, \mathrm{CaCl}_2$, and $\mathrm{BeCl}_2$ (c) the lowest first ionization energy among the elements $\mathrm{Rb}, \mathrm{K}$, and $\mathrm{Li}$ (d) the smallest among $\mathrm{Al} \mathrm{Al}^{+}$, and $\mathrm{Al}^{3+}$ (e) the largest among $\mathrm{Cs}^{+}, \mathrm{Ba}^{2+}$, and $\mathrm{Xe}$

Why is boron limited to a maximum coordination number of four in its compounds?

Write a balanced equation for the reaction of elemental boron with each of the following (most of these reactions require high temperature): (a) $\mathrm{F}_2$ (b) $\mathrm{O}_2$ (c) $\mathrm{S}$ (d) $\mathrm{Se}$ (e) $\mathrm{Br}_2$

ame each of the following compounds: (a) $\mathrm{TeO}_2$ (b) $\mathrm{Sb}_2 \mathrm{~S}_3$ (c) $\mathrm{GeF}_4$ (d) $\mathrm{SiH}_4$ (e) $\mathrm{GeH}_4$

Silicon reacts with sulfur at elevated temperatures. If $0.0923 \mathrm{~g}$ of silicon reacts with sulfur to give $0.3030 \mathrm{~g}$ of silicon sulfide, determine the empirical formula of silicon sulfide.