Answer:
Carbon and silicon are both in Group 14 of the periodic table, which means they have similar electronic configurations and therefore similar bonding properties. However, the difference in melting and sublimation temperatures of their oxides, silicon oxide and solid carbon dioxide, respectively, can be attributed to differences in their structure and bonding.
Silicon oxide (SiO2) has a giant covalent structure, in which each silicon atom is covalently bonded to four oxygen atoms and each oxygen atom is covalently bonded to two silicon atoms. This gives rise to a three-dimensional network of strong covalent bonds, which requires a large amount of energy to be broken. Therefore, silicon oxide has a high melting point of 2440°C because a lot of energy is required to overcome the strong covalent bonds and melt the solid.
On the other hand, solid carbon dioxide (CO2) has a molecular structure, in which each carbon atom is double bonded to two oxygen atoms. The carbon dioxide molecules are held together by weak intermolecular forces, such as Van der Waals forces, which are much weaker than the strong covalent bonds present in silicon oxide. As a result, solid carbon dioxide can sublime at -70°C, without melting into a liquid, because the intermolecular forces can be overcome by relatively low energy input.
In summary, the difference in melting and sublimation temperatures of silicon oxide and solid carbon dioxide can be explained by the difference in their bonding types and structures. Silicon oxide has a giant covalent structure with strong covalent bonds that require a large amount of energy to break, resulting in a high melting point. Solid carbon dioxide has a molecular structure held together by weak intermolecular forces, which can be overcome by relatively low energy input, resulting in a low sublimation point.