Group IVA The Carbon Family

In the following subsections, we will look at carbon and silicon. Both elements have many important compounds that exhibit tetrahedral sp ) bonding. Carbon, however, also has many compounds that contain multiple bonds in which sp and sp bonding occurs silicon has very few such compounds. Another difference in the bonding characteristics of these elements is silicon s ability to use sp cf hybrid orbitals in octahedral bonding, which is not possible with carbon. The hexafluorosUicate ion, SiFs, is an example of such bonding. 

One of the most important features of the carbon atom is its ability to bond to other carbon atoms to form chains and rings of enormous variety. The covalent bonding of two or more atoms of the same element to one another is referred to as catenation. 

Although other elements display catenation, none show it to the same degree as carbon. Millions of carbon compounds are known, most classified as organic. These can be thought of as derivatives of hydrocarbons, each consisting of a chain (or more complicated arrangement) of carbon atoms to which hydrogen atoms are bonded. In this section, we will confine ourselves to the element and its oxides and carbonates. 

Allotropes of Carbon Until recently, carbon was thought to occur in only two principal allotropic forms diamond and graphite. Both allotropes are covalent network solids, whose structures we discussed in detail in Section 11.8. In diamond, each carbon atom is tetrahedrally (sp ) bonded to four other carbon atoms. To move one plane of atoms in the diamond crystal relative to another requires the breaking of many strong carbon-carbon bonds. Because of this, diamond is one of the hardest substances known. As a pure substance, diamond is colorless, although natural diamond may be colored by impurities. 

In 1985 a third allotropic form of carbon, known as buckminsterfuUerene (C o), was discovered. This molecular form of carbon has been studied intensively. The molecule has a stable soccer-ball structure, described in Chapter 13. 

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Germanium is a metalloid. A metalloid is an element that has characteristics of both metals and non-metals. Germanium is located in the middle of the carbon family, which is Group 14 (IVA) in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. Carbon and silicon are above germanium and tin and lead are below it. 

For representative elements the number of valence electrons in an atom corresponds to the number of the group or family in which the atom is found. For example, elements such as hydrogen and sodium (in fact, all alkali metals. Group lA or 1) have a valence of 1 (or one valence electron). From left to right in period 2, beryllium. Be (Group llA or 2), has two valence electrons boron, B (Group lllA or 3), has three carbon, C (Group IVA or 4), has four and so forth. 

The answer is B. The given configuration is that of Group IVA (carbon family). 

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