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?

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.

Classify each of the following molecules as polar or nonpolar. You may wish to review the chapter on chemical bonding. (a) $\mathrm{SiH}_4$ (b) $\mathrm{Si}_2 \mathrm{H}_6$ (c) $\mathrm{SiCl}_3 \mathrm{H}$ (d) $\mathrm{SiF}_4$ (e) $\mathrm{SiCl}_2 \mathrm{~F}_2$

Describe the hybridization and the bonding of a silicon atom in elemental silicon.

Describe the hybridization of silicon and the molecular structure of the following molecules and ions: (a) $\left(\mathrm{CH}_3\right)_3 \mathrm{SiH}$ (b) $\mathrm{SiO}_4^{4-}$ (c) $\mathrm{Si}_2 \mathrm{H}_6$ (d) $\mathrm{Si}(\mathrm{OH})_4$ (e) $\mathrm{SiF}_6{ }^{2-}$

Write a Lewis structure for each of the following molecules and ions: (a) $\left(\mathrm{CH}_3\right)_3 \mathrm{SiH}$ (b) $\mathrm{SiO}_4^{4-}$ (c) $\mathrm{Si}_2 \mathrm{H}_6$ (d) $\mathrm{Si}(\mathrm{OH})_4$ (e) $\mathrm{SiF}_6$ 2-

Using only the periodic table, write the complete electron configuration for silicon, including any empty orbitals in the valence shell. You may wish to review the chapter on electronic structure.

Describe the hybridization of boron and the molecular structure about the boron in each of the following: (a) $\mathrm{H}_3 \mathrm{BPH}_3$ (b) $\mathrm{BF}_4{ }^{-}$ (c) $\mathrm{BBr}_3$ (d) $\mathrm{B}\left(\mathrm{CH}_3\right) 3$ (e) $\mathrm{B}(\mathrm{OH})_3$