Polar covalent compound illustration

The relationship between submicroscopic structure and macroscopic properties is an important part of the study of chemistry. Use an ionic compound, a nonpolar covalent compound, and a polar covalent compound to illustrate this relationship. (Chapter 1)... 

FIGURE 10.4 An illustration of a strong acid dissolving in water. The acid is a polar covalent compound, like sugar, but when it dissolves in water, it ionizes—that is, the hydrogen atoms break away from the molecule, forming hydrogen ions (+ ions) and - ions. It is a total, complete ionization. 

Definitions. Define and illustrate the following terms (a) octet rule, (b) Lewis symbol, (c) ionic bond, (d) covalent bond, (e) crystal lattice energy, (f) Iree radical, (g) network covalent compound, (h) electronegativity, (i) polar molecule, (j) dipole moment, (k) formal charge, (1) oxidation number, (m) hydrogen bond, (n) dipole-dipole attraction, (o) London forces. 

FIGURE 10.3 An illustration of a poiar covalent compound, such as sugar, dissolving in water. The water molecules, by virtue of their polar nature, pull the polar sugar molecules from the crystal array, and the compound dissolves. 

Co-ordination. The formation of a co-ordinate covalent bond, that Is, the formation of a chemical bond in which both the shared electrons come from one of the participating atoms, hence a bond of some polarity chemical linkage of the type illustrated by the formation of hydrates, ammonates, chelate compounds. 

In molecular crystals or in crystals composed of complex ions it is necessary to take into account intramolecular vibrations in addition to the vibrations of the molecules with respect to each other. If both modes are approximately independent, the former can be treated using the Einstein model. In the case of covalent molecules specifically, it is necessary to pay attention to internal rotations. The behaviour is especially complicated in the case of the compounds discussed in Section 2.2.6. The pure lattice vibrations are also more complex than has been described so far . In addition to (transverse and longitudinal) acoustical phonons, i.e. vibrations by which the constituents are moved coherently in the same direction without charge separation, there are so-called optical phonons. The name is based on the fact that the latter lattice vibrations are — in polar compounds — now associated with a change in the dipole moment and, hence, with optical effects. The inset to Fig. 3.1 illustrates a real phonon spectrum for a very simple ionic crystal. A detailed treatment of the lattice dynamics lies outside the scope of this book. The formal treatment of phonons (cf. e(k), D(e)) is very similar to that of crystal electrons. (Observe the similarity of the vibration equation to the Schrodinger equation.) However, they obey Bose rather than Fermi statistics (cf. page 119). 

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