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Types of Chemical Bonds Explained

May 21, 2025

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, Hâ‚‚, Oâ‚‚, Clâ‚‚, NH₃, CHâ‚„ 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.