`CO_2` is gas but `SiO_2` is solid at room temperature. Why?

Explanation

In `CO_(2)` the C-atom is linked to oxygen through one sigma bond and one pi-bond.
`O = C=O`
`pi` - bond in `CO_(2)` is formed due to sidewise overlapping of 2p orbitals of carbon and oxygen `CO_(2)` exists as an independent molecule, Weak Vander Waal.s forces of attraction occur among `CO_(2)`, molecules. In case of `SiO_(2)` , 3p orbital of Si cannot overlap sidewise with 2p orbital of C-atom. This is because of difference in their energies. Two atoms can be linked by single bond. A network like structure of solid is formed as shown in fig.