Final answer:
The melting point of SiO2 is higher than that of CO2 because SiO2 is a covalent network solid with a strong three-dimensional bond network, whereas CO2 consists of individual molecules held together by weak intermolecular forces.
Step-by-step explanation:
The huge difference in melting points between silicon dioxide (SiO2) and carbon dioxide (CO2) is due to their different structures and bonding. Silicon dioxide is a covalent network solid where each silicon atom is bonded to four oxygen atoms in a tetrahedral structure, creating a strong, three-dimensional, continuous network. This results in a much higher melting point of 1700°C since breaking the continuous network requires a significant amount of energy.
In contrast, carbon dioxide consists of individual CO2 molecules held together by very weak intermolecular forces, making it much more volatile and having a low melting point of -78°C. Here, the molecules have strong double bonds within, but between the molecules, the forces are weak, thus requiring much less energy to overcome these forces and melt the solid.