AQA GCSE Chemistry: Topic 2 - Chemical Bonds and Types of Bonding

Overview of Chemical Bonds

• Compounds are substances where two or more elements are chemically combined.
• Three types of strong chemical bonds:
  • Ionic Bonds
  • Covalent Bonds
  • Metallic Bonds

Ionic Bonding

• Occurs in compounds formed from metals and non-metals.
• Particles involved are oppositely charged ions.
• Process:
  • Electrons from the outer shell of a metal atom are transferred to a non-metal atom.
  • Metal atoms lose electrons, forming positively charged ions.
  • Non-metal atoms gain electrons, forming negatively charged ions.
• Ion Properties:
  • Atoms that lose or gain electrons.
  • Metals in Groups 1 and 2, and non-metals in Groups 6 and 7, achieve a full outer electron shell, similar to noble gases.
• Representation:
  • Electron transfer is often shown using dot and cross diagrams.

Ionic Compounds

• Structure:
  • Form a giant 3D structure of ions.
  • Held together by strong electrostatic forces between oppositely charged ions.
  • Forces act in all directions.
• Example: Sodium chloride (NaCl) with Na+ and Cl- ions.

Covalent Bonding

• Characterized by atoms sharing pairs of electrons.
• Occurs in:
  • Most non-metallic elements.
  • Compounds of non-metals.
• Examples:
  • Small molecules like HCl, H₂, O₂, Cl₂, NH₃, CH₄ with strong internal covalent bonds.
  • Polymers, which are large covalently bonded molecules.
  • Giant covalent structures (macromolecules), such as diamond and silicon dioxide, with lattice arrangements.
• Diagrams: Use dot and cross, repeat units, single line bonds, and ball and stick models to represent structures.

Metallic Bonding

• Structure:
  • Positive ions (metal atoms that have lost electrons) and delocalised electrons.
  • Electrons lost from atoms form a delocalised electron system.
  • Delocalised electrons can move freely through the structure.
• Bond Characteristics:
  • Delocalised electrons are shared across the structure, creating strong metallic bonds.