Ugljik, silicij, kisik: kemijska analogija živog i neživog

Carbon and silicon are similar chemical elements, being the members of the same, 14 th (4B), group of the periodic system; not only in science fiction but also in serious scientific works could there be found speculations about the possibility of extra-terrestrial life based on silicon. In this paper, the physical and chemical properties of carbon and silicon, as well as their respective compounds were compared (alkanes – silanes, cyclic hydrocarbons – cyclosilicates, heterocyclic compounds – alumosilicates). Their geochemistry shows mutual dependence of carbon and sil - icon circulations. Moreover, comparison of silica (quartz) with water (ice) points to unexpected similarities of the two minerals.