91Ó°ÊÓ

Using a reference source, we find the following information for our pairs of compounds: (a) W: Melting point = 3422 °C; Boiling point = 5555 °C \(\mathrm{WF}_{6}\): Melting point = 2.65 °C; Boiling point = 17.4 °C (b) \(\mathrm{SO}_{2}\): Melting point = -72.7 °C; Boiling point = -10.0 °C \(\mathrm{SF}_{4}\): Melting point = -120.2 °C; Boiling point = -31.67 °C (c) \(\mathrm{SiO}_{2}\): Melting point = 1610 °C; Boiling point = 2230 °C \(\mathrm{SiCl}_{4}\): Melting point = -68.2 °C; Boiling point = 57.2 °C

Next, let's examine the structures for each compound and determine the type of bonding involved: (a) W is a metallic element, and its bonding is metallic. \(\mathrm{WF}_{6}\) is a hexafluoride, consisting of one tungsten (W) atom bonded to six fluorine (F) atoms. The bonding in \(\mathrm{WF}_{6}\) is primarily covalent. (b) \(\mathrm{SO}_{2}\) is a molecule with a bent structure where sulfur (S) forms double bonds with two oxygen (O) atoms. The bonding in \(\mathrm{SO}_{2}\) is covalent. \(\mathrm{SF}_{4}\) is a molecule with a tetrahedral 'see-saw' structure, with one sulfur (S) atom bonded to four fluorine (F) atoms. The bonding is covalent. (c) \(\mathrm{SiO}_{2}\) is a network solid where each silicon (Si) is tetrahedrally coordinated to four oxygen (O) atoms. The bonding in \(\mathrm{SiO}_{2}\) is primarily covalent. \(\mathrm{SiCl}_{4}\) is a molecule with a tetrahedral structure where one silicon (Si) atom is bonded to four chlorine (Cl) atoms. The bonding is covalent.

Now, let's explain the observed differences in melting and boiling points for each pair based on their bonding and structures: (a) The difference between W and \(\mathrm{WF}_{6}\) can be attributed to the metallic bonding in W and covalent bonding in \(\mathrm{WF}_{6}\). Metallic bonding results in a dense, closely-packed arrangement of atoms with delocalized electrons, leading to strong bonds and high melting and boiling points. In contrast, \(\mathrm{WF}_{6}\) is a covalent compound with molecular bonding, which typically results in weaker interactions and thus lower melting and boiling points. (b) The difference between \(\mathrm{SO}_{2}\) and \(\mathrm{SF}_{4}\) is due to their molecular structures. \(\mathrm{SO}_{2}\) has a bent structure with polar bonds, which leads to stronger dipole-dipole interactions compared to \(\mathrm{SF}_{4}\)'s tetrahedral 'see-saw' structure. The stronger interactions in \(\mathrm{SO}_{2}\) result in higher melting and boiling points. (c) The difference between \(\mathrm{SiO}_{2}\) and \(\mathrm{SiCl}_{4}\) stems from the fact that \(\mathrm{SiO}_{2}\) is a network solid with a continuous, covalently-bonded structure, resulting in high melting and boiling points. \(\mathrm{SiCl}_{4}\), as a covalently-bonded molecular structure, experiences weaker forces (such as London dispersion forces) between its molecules, giving it much lower melting and boiling points. In summary, the major differences in melting and boiling points among the compounds can be attributed to differences in bonding types and chemical structures.