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MDCAT Chemistry QUESTION #7796
Question 1

Third period element that forms a protective oxide coating preventing further reaction:

  • Al✔️
  • Mg
  • Na
  • Si
Correct Answer Explanation

Aluminium forms a thin, adherent Al₂O₃ layer that is passivating. MgO is also protective but less complete; Na oxide is reactive; SiO₂ is not typical for rapid reaction.