Silicon doesn't have a tendency to form pπ−pπ multiple bonds either with itself or with other atoms due to its larger size and smaller electronegativity. This can be proved by the following facts : (i) Elemental Si is known only in 'diamond structure and no form of Si is known to possess graphite structure. (ii) CO2, containing C=O bonds is a gas while SiO2 is a solid which contains infinite 3 -D network of Si−O bonds.