The chemistry of silicon differs markedly from that of carbon. Although carbon and silicon both have a normal valence of four and are similar in some ways, the differences between the chemical properties of their compounds are more striking than the similarities. There are groups of compounds where the differences are easily seen.

1. The oxides:The oxides of the two elements have very different properties. Carbon dioxide, CO2is a gas at room temperature and atmospheric pressure. Silicon dioxide, usually known as silica, has the empirical formula SiO2, but it is a solid with a very high melting point, not a gas. The reason for the difference is that silica consists of an extended network of silicon and oxygen atoms.

2. The hydrides:The hydrides of silicon have formulae such as SiH4, Si2H6etc, and are called silanes. These compounds are analogous to the alkanes CH4, C2H6etc. The reason that silanes are much more reactive than alkanes is not related to any “weakness” in the bonds.