`SiO_2` is a solid while `CO_2` is a gas - explain.

Explanation

Carbon dioxide molecules are held together only by weak Vander Waal.s forces and hence it exists as a gas at ordinary temperature.
Silicon has a three-dimensional infinite structure, in which silicon atom is tetrahedrally. bonded to two silicon atoms by covalent bonds. The whole crystal of silica thus exists as a giant molecule and hence silica is a high melting solid