Oxygen compounds, crystal structures

Oxygen and fluorine ions have very similar ionic radii. This steric similarity ensures relatively easy substitution of the oxygen in the compounds, by fluorine ions. Such substitution opens up huge possibilities for the synthesis of oxyfluoride compounds with desired crystal structure and properties. 

Figure 1. The crystal structure of Zr2(0H)2(SO4)3(H2O)4> reprinted with permission from Ref. 5, copyright 1966, American Chemical Society. Zirconium atoms are shown as solid circles, oxygen atoms as open circles. The Pu compound is isomorphous, Zr being replaced by Pu. la shows the manner in which the bridging sulfates link Pu atoms to form layers, lb shows the manner in which layers are linked through the double hydroxide bridges.

C.19 Aluminum oxide, alumina, exists in a variety of crystal structures, some of which are beautiful and rare. Write the formula for aluminum oxide, which is a binary compound of aluminum and oxygen. The mass of a rectangular slab of aluminum oxide of dimensions 2.5 cm X 3.0 cm X 4.0 cm is 102 g. What is the density of aluminum oxide ... 

Thus, l,6-methano[10]annulene (77) and its oxygen and nitrogen analogs 78 and 79 have been prepared and are stable compounds that undergo aromatic substitution and are diatropic. For example, the perimeter protons of 77 are found at 6.9-7.3 5, while the bridge protons are at —0.5 5. The crystal structure of 77 shows that the perimeter is nonplanar, but the bond distances are in the range 1.37-1.42A. It has therefore been amply demonstrated that a closed loop of 10 electrons is an aromatic system, although some molecules that could conceivably have such a system are too distorted from planarity to be aromatic. A small distortion from planarity (as in 77) does not prevent aromaticity, at least in part because the s orbitals so distort themselves as to maximize the favorable (parallel) overlap of p... 

Talc is a hydrated magnesium silicate, Mg6(Si802o)(OH)4. It is a layerd compound like mica. One layer of its crystal structure is shown schematically in Figure 11.3. Such layers are stacked up like playing cards in real crystals. Notice that the top and bottom of the layer consist of slicate tetrahedra with oxygen... 

Perovskites are compounds of the ABC3- type where C is often oxygen, but not always. Figure 11.6 shows two versions of the perovskite crystal structure... 

Because of its relatively loosely bound outermost electron, and its small size, boron reacts readily with other atoms (including itself) to form a variety of crystal structures. The B-B bond is only about 12 percent longer (1.75 A) than the very strong C—C bond (1.54 A). It not only forms very hard compounds with carbon and nitrogen, but also with oxygen. 

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