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?

Is the reaction of rubidium with water more or less vigorous than that of sodium? How does the rate of reaction of magnesium compare?

What does it mean to say that mercury(II) halides are weak electrolytes?

Rank the ions in each set in order of decreasing size, and explain your ranking:

Sr2+, Ba2+, Cs+.

Is it possible for a complex of a metal in the transition series to have six unpaired electrons? Explain.

Is it possible for a complex of a metal in the transition series to have six unpaired electrons? Explain.

Draw the crystal field diagrams for $\left[\mathrm{Fe}\left(\mathrm{NO}_2\right)_6\right]^{4-}$ and $[\mathrm{FeF} 6]^{3-}$. State whether each complex is high spin or low spin, paramagnetic or diamagnetic, and compare $\Delta_{\text {oct }}$ to $P$ for each complex.

Draw the crystal field diagrams for $\left[\mathrm{Fe}\left(\mathrm{NO}_{2}\right)_{6}\right]^{4-}$ and $\left[\mathrm{FeF}_{6}\right]^{3-}$. State whether each complex is high spin or low spin, paramagnetic or diamagnetic, and compare $\Delta_{\mathrm{oct}}$ to P for each complex.

Determine the number of unpaired electrons expected for $\left[\mathrm{Fe}\left(\mathrm{NO}_{2}\right)_{6}\right]^{3-}$ and for $\left[\mathrm{FeF}_{6}\right]^{3-}$ in terms of crystal field theory.

Determine the number of unpaired electrons expected for $\left[\mathrm{Fe}\left(\mathrm{NO}_2\right)_6\right]^{3-}$ and for $[\mathrm{FeF} 6]^{3-}$ in terms of crystal field theory.

Predict whether the carbonate ligand $\mathrm{CO}_3{ }^{2-}$ will coordinate to a metal center as a monodentate, bidentate, or tridentate ligand.

Predict whether the carbonate ligand $\mathrm{CO}_{3}^{2-}$ will coordinate to a metal center as a monodentate, bidentate, or tridentate ligand.

Iron(III) forms octahedral complexes. Sketch the structures of all the distinct isomers of [Fe(en)2Cl2]^+, indicating which pairs of structures are mirror images of each other.

Indicate the coordination number for the central metal atom in each of the following coordination compounds: (a) $\left[\operatorname{Pt}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2} \mathrm{Br}_{2}\right]$ (b) $\left[\operatorname{Pt}\left(\mathrm{NH}_{3}\right)(\mathrm{py})(\mathrm{Cl})(\mathrm{Br})\right]$ (py = pyridine, $\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}$) (c) $\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right]$ (d) $\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)(\mathrm{py})(\mathrm{Cl})(\mathrm{Br})\right]$ (e) $\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]$ (f) $\left[\mathrm{Fe}(\mathrm{en})_{2}(\mathrm{CN})_{2}\right]^{+}$ (en = ethylenediamine, $\mathrm{C}_{2} \mathrm{H}_{8} \mathrm{N}_{2}$)