Giant covalent elements form gaseous oxides despite high melting points

Steps:

• High melting point indicates strong, extended bonding in the element, ruling out weak intermolecular forces.
• Gaseous oxide at room temperature suggests the oxide is simple molecular, typical of non-metal oxides like CO2.
• Non-metals with giant covalent structures (e.g., carbon, silicon) have high melting points from vast covalent networks.
• Thus, the element must have giant covalent bonding to match both properties.

Why A is correct:

• Giant covalent structures feature continuous strong covalent bonds, yielding high melting points; non-metals form simple molecular oxides that are gases due to weak forces between molecules.

Why the others are wrong:

• B. Ionic: Oxides are solid ionic lattices with high melting points, not gases.
• C. Metallic: Metals form solid ionic oxides; melting points vary but don't typically yield gaseous oxides.
• D. Simple molecular: Low melting points from weak van der Waals forces contradict the high melting point.

Final answer: A