Period 3 Oxides and Chlorides Bonding and Reactivity

Steps:

• Classify oxides: Na₂O, MgO, Al₂O₃ ionic (basic, react with HCl to form salts); SiO₂, P₄O₁₀ covalent (SiO₂ inert to dilute HCl, P₄O₁₀ reacts but not ionic).
• Evaluate statement 1: Ionic oxides (Na, Mg, Al) dissolve in dilute HCl, producing H₂ or salts, confirming reactivity.
• Evaluate statement 2: NaCl neutral in water; MgCl₂ slightly acidic (Mg²⁺ hydrolysis); AlCl₃ strongly acidic (Al³⁺ hydrolysis to [Al(H₂O)₆]³⁺), so not all neutral.
• Evaluate statement 3: Most electronegative are Si (1.8) and P (2.1); SiCl₄ and PCl₅ covalent (low electronegativity difference with Cl).

Why C is correct:

• C selects statements 1 and 3, matching ionic oxide acidity (Brønsted-Lowry: bases accept H⁺ from HCl) and covalent chlorides (Pauling rule: ΔEN < 1.7 indicates covalent bonding).

Why the others are wrong:

• A includes 2, but AlCl₃ hydrolysis produces acidic solutions.
• B includes 2, ignoring hydrolysis acidity in MgCl₂ and AlCl₃.
• D excludes 1, but ionic oxides react per acid-base theory.

Final answer: C