The Chemical Properties of Silicon and Carbon

There are no natural organic silicon compounds all of them have been created in the chemical laboratory. 

The chemical dissimilarity between carbon and silicon is due to the differences between the periods in which they are found. The silicon nucleus, in the second short period, attracts its outer electrons less strongly than that of carbon, in the first short period, because the L-shell electrons effectively screen the nuclear charge of silicon. Moreover, the chemistry of silicon is affected by the availability of empty 3d orbitals, the energy of which is not much higher than the silicon 3s and 3p orbitals. These make it easy for silicon to form 5- and 6-coordinated complexes, in contrast to carbon. 

Carbon and silicon differ in atomic size (covalent radii rc = 77 pm rj = 117 pm) and electronegativity [1] (xc = 2.50 Xsi = 1-74). The electronegativity of silicon is peculiar. This finding was recently corroborated, and a new electronegativity scale for the group IV elements estimated from the observed bond distances in the bivalent and tetravalent halides. The predicted values are C, 2.6 Si, 1.9 Ge, 2.5 and Sn, 2.3 [2]. Table 1.1 shows that the differences between the covalent radii and the electronegativities of homologoues first and second period elements are similar to those of carbon and silicon. 

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