CARBON, SILICON AND GERMANIUM
The elements
s2p2 the nonmetallic elements of group 14 can create compounds along with four tetrahedrally directed covalent bonds, with the valence electron configuration. Only carbon creates strong multiple bonds, and its compounds depict many variations in structure and properties from those of Ge and Si. Such as the metallic elements of the group (Sn and Pb), germanium has a number of stable divalent compounds.
The abundances of the elements through mass in the crust are: C about 480 p.p.m., Si 27% (second only to oxygen) and Ge 2 p.p.m. Carbon is exist as carbonate minerals and in smaller amounts like the element and in hydrocarbon deposits. It is significant in the atmosphere (like the greenhouse gas CO2;) and is the main element of life. Silicate minerals are the leading chemical compounds of the crust and of the fundamental mantle. Germanium is extensively but thinly distributed in sulfide and silicate minerals. In the tetrahedrally bonded diamond structure, all three elements can crystallize. Si and Ge are semiconductors. Carbon has another allotropes. Graphite is the thermodynamically stable type at ordinary pressures, diamond at high pressures. More currently discovered forms involve buckminsterfullerene C60, higher fullerenes like C70, and nanotubes composed by graphite sheets rolled into cylinders. In these structures carbon creates 3 σ bonds, the left valence electron being in delocalized π orbitals analogous to those within benzene.
The elements can be produced through reduction of oxides or halides. Highly divided carbon black is employed as a catalyst and impure carbon (coke) and black pigment for reducing several metal oxides (example in the manufacture of iron;). Pure silicon prepared through reduction of SiCl4 with Mg is employed in electronics ('silicon chips') even though much larger quantities of impure Si are employed in steels.