Period 3 oxides' reactivity with water

Steps:

• Identify oxides: sodium oxide (Na₂O), aluminum oxide (Al₂O₃), silicon dioxide (SiO₂).
• Na₂O is basic, reacts vigorously with water to form NaOH solution.
• Al₂O₃ is amphoteric, insoluble and does not react with water.
• SiO₂ is acidic, insoluble and does not react with water.

Why D is correct:

• Na₂O + H₂O → 2NaOH (basic oxide reaction), while Al₂O₃ and SiO₂ remain unreactive due to their structures.

Why the others are wrong:

• A: SiO₂ is acidic, not amphoteric.
• B: SiO₂ is giant covalent, not simple molecular.
• C: All three oxides have high melting points due to strong bonding.

Final answer: D