Among the following oxides, which is the MOST acidic?

1. Across period 3 the acid-base character of oxides shifts from basic to acidic. 2. Na₂O is a strong base because Na is highly metallic. 3. MgO is still basic, though less so than Na₂O. 4. Al₂O₃ is amphoteric, sitting at the borderline. 5. Non-metallic oxides such as SO₃ and Cl₂O₇ are clearly acidic. 6. Cl₂O₇ comes from the most electronegative element on this list. 7. So Cl₂O₇ is the most acidic of the four oxides. _Source: Selina Concise Chemistry ICSE Class 10, Ch 1 'Periodic Table' (aplustopper.com extract)_