ABSTRACT
Carbon and silicon share several similarities in their electronic structure, since they are both in the fourth column of the periodic table, having the same electronic con guration of valence electrons (2s22p2 for carbon, 3s23p2 for silicon). Yet, their chemistries and “usefulness” are very di erent. Carbon is essential for life, while silicon is essential for modern electronic technology. Only in science ction, silicon could be related with some sort of “life,” although technology based on carbon is not totally unrealistic (e.g., carbon nanotubes). e structural chemistry of carbon at the molecular and nanoscale level is dominated by planar aromatic structures such as benzene and two-dimensional hollow spherical cages or fullerenes whereas for silicon, three-dimensional pyramidal and diamond-like structures predominate. is is due formally to the di erent rows (carbon is the rst, silicon in the second) of the periodic table. As a consequence, the size of the atoms and the promotion energies between s and p valence orbitals (2s-2p for C, 3s-3p for Si) are di erent, a ecting the orbital overlap and hybridization. us, carbon usually prefers strong π covalent bonds blended in sp2 (or sp) hybrid orbitals, which are manifested as double and triple bonds, while silicon normally forms covalent σ bonds between sp3 hybrid orbitals.
