* Molecular solids are formed by molecules held together by intermolecular forces (like van der Waals forces or hydrogen bonding). These forces are relatively weak.
* Covalent network solids are formed by atoms linked together by a continuous network of strong covalent bonds.
In the case of CO2:
* Each carbon atom in CO2 forms double bonds with two oxygen atoms.
* These bonds are strong covalent bonds.
* The resulting CO2 molecules have a linear shape, and they interact with each other only through weak van der Waals forces.
* However, at very low temperatures (below -78°C), CO2 molecules arrange themselves in a specific, ordered structure where the carbon atoms are linked to each other through weak van der Waals forces. This arrangement is still considered a molecular solid, but it's not the typical state of CO2 at room temperature.
Therefore, while CO2 does form a molecular solid at very low temperatures, it's more accurately described as a covalent network solid at room temperature due to the strong covalent bonds within the CO2 molecules.
