Notes on Period 3 Elements - AQA Chemistry A-level

Properties of Period 3 Metals

• Sodium and Magnesium
  • React ionically to form positive ions.
  • Sodium: Forms 1+ ions, more reactive due to requiring less energy to ionize (loses one electron).
  • Magnesium: Forms 2+ ions, less reactive as it requires losing two electrons.
  • Reaction speed increases with steam, resulting in a violent reaction with magnesium burning with a bright white flame, producing hydrogen and magnesium oxide.

Period 3 Oxides

• Elements react with oxygen to form oxides in their highest oxidation state (usually the same as group number).
• Sulfur can form SO₃ with oxidation state +6 (requires high temperatures and a catalyst).

Oxides Table:

Reactions with Water

• Ionic Oxides: Combine with water to form alkaline solutions (pH 10-14).
• Covalent Oxides (Sulfur and Phosphorus): Combine with water to form acidic solutions (pH 0-2).
  • In solution, these acids dissociate into H⁺ ions and ions of conjugate base.

Acid-base Reactions

• Basic, Ionic Oxides: React with acids to produce a salt and water (neutralization reaction).
• Acidic, Covalent Oxides: React with bases to produce a salt and water (neutralization reaction).

Amphoteric Nature of Aluminium Oxide

• Partially ionic and covalent bonding.
• Insoluble in water as ions don't dissociate.
• Acts as both acid and base, known as amphoteric.
  • Participates in neutralization reactions to form salt and water.