Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 95

Covalent bonding can lead to two different types of structures. These are called simple covalent (or simple molecular) or giant covalent (or giant molecular) structures. The main difference between simple molecular covalent bonding and giant covalent bonding is that a simple molecule is just that: a small molecule that contains covalent bonds. Examples of molecules that have simple molecular bonding are oxygen (O₂), methane (CH₄), chlorine (Cl₂), and ethanol (C₂H₆O). Giant covalent bonding leads to extended repeated units such as in silicon dioxide (SiO₂) and graphite and diamond (both elemental forms of carbon). A substance that has a giant covalent structure is much more complex and contains an extended array of bonds. This type of bonding does not result in discrete molecules because the bonding is repeated throughout the structure. The structures formed are not molecules as the bonding continues repeatedly in three dimensions. The structures of diamond, silicon dioxide, and graphite are shown in Figure 2.11.

Figure 2.11 (a) Bonding in diamond; (b) bonding in silicon dioxide; (c) two‐dimensional bonding in graphite, looking down from above; (d) three‐dimensional bonding in graphite, looking through the layers.