Catenation elements other than carbon

The outstanding characteristic of the chemistry of carbon is its ability to catenate. Catenation is the bonding of atoms of the same element to each other, and carbon shows this tendency to a far greater extent than any other element. Even its elemental forms are characterized by extended structural units. Graphite is the most common form of elemental carbon, but it exists in two forms, both of which are composed of layers. One form has the layers oriented as shown in Figure 10.1. 

Catenation is defined as the self-linking of an element to form chains and rings. Carbon, then, given the above discussion, is the all-time champion catenator, much better than silicon (or sulfur, boron, phosphorus, germanium, and tin, the other elements that show this ability). Why should this be so A comparison of the relevant carbon and silicon bond energies as shown below is helpful ... 

Carbon atoms have the ability to bond to themselves to a greater extent than those of any other element. Known as catenation, this ability gives rise to the several allotropic forms of the element. The most common form of elemental carbon is graphite, which has the layered structure shown in Figure 13.11. 

Apart from carbon, catenation does not occur to any great degree in the chemistry of the other elements. Si and Ge do form hydrides that might be compared with the lighter hydrocarbons, but they are not as stable. Catenation in these elements involves the formation of Si-Si and Ge-Ge covalent bonds, which are longer and therefore weaker than C-C bonds. 

With carbon forming the basis for the colossal number of organic compounds, it is interesting to consider whether silicon or other members of this group can form an equally vast array of compounds. This does not seem the case the ability to catenate (form bonds with other atoms of the same element) is much lower for the other Group 14 elements than for carbon, and the hydrides of these elements are also much less stable. 

Why did life evolve based on the chemistry of carbon Why is life not based on some other element The answer may not be simple, but we know that life—in order to exist— must entail complexity, and carbon chemistry is clearly complex. The number of compounds containing carbon is greater than the number of compounds containing aU of the other elements combined. The reasons for carbon s unique and versatile behavior include its ability to form four covalent bonds, its abihty to form double and triple bonds, and its tendency to catenate (that is, to form chains). 

Carbon s Tendency to Catenate Carbon, more than any other element, can bond to itself to form chain, branched, and ring stractures. 

---