`CO_(2)` is a gas while `SiO_(2)` is a solid. Explain.

Answer

Carbon because of its small size and higher electronegitivity than silicon forms `ppi-ppi` double bonds with `O`-atoms to form `CO_(2)` molecule.These molecules of `CO_(2)` are held together by weak van der Waals forces of attraction which can be easily overcome by collisions of the molecules at room temperature.Consequenctly, `CO_(2)`, is a gas.Silicon, on the other hand, because of its bigger size and lower electronegativity than carbon has little tendency to form `ppi-ppi` double bonds with `O`-atoms.Instead, each silicon atom forms four single covalent bonds with `O`-atoms which are tetrahedrally arranged around it leading to the formation of a three-dimensional network structure, To break these covalent bonds, a large amount of energy is needed and hence `SiO_(2)` is a high melting solid.