Classifying period 3 oxide structure from solubility and stability

Steps:

• Identify W as a period 3 non-metal, forming oxide X with small molecular structure based on position.
• Note X is solid and white, ruling out gaseous oxides like SO2.
• Thermal stability indicates strong bonding within units, not weak intermolecular forces alone.
• Slight solubility in water points to ionic bonding allowing limited ion dissociation, unlike fully covalent or giant structures.

Why C is correct:

• Ionic bonding within small molecules fits the definition of compounds like certain polymeric oxides with discrete units that dissolve partially via ion formation.

Why the others are wrong:

• A: Giant covalent structures, like SiO2, are insoluble in water due to no ion formation.
• B: Three-dimensional covalent lattice with strong double bonds, like diamond or SiO2, lacks solubility from rigid network.
• D: Strong ionic lattice forms extended crystals, leading to negligible solubility like MgO, not slight.

Final answer: C