Free Science Lessons: Metallic Bonding and Properties of Metals

Objectives

• Describe metallic bonding.
• Explain the properties of pure metals and alloys.

Key Concepts

Metal Structure

• Metals in Chemistry: Metals are significant in chemistry with examples such as a gold bar (pure gold) and a guitar string (an alloy).
• Stability of Atoms: Atoms achieve stability by having a full outer energy level.
  • Ionic Bonding: Occurs when a metal atom reacts with a non-metal atom.
  • Covalent Bonding: Occurs between two non-metal atoms.

Bonding in Metals

• Structure: Metals have a giant structure with atoms arranged in regular layers.
• Delocalized Electrons: Electrons in the outer energy level are delocalized.
  • Example: Lithium atoms have delocalized outer electrons.
• Sea of Delocalized Electrons: Free electrons throughout the structure, creating a sea of electrons.
• Positive Metal Ions: Metal atoms lose their outer electrons, becoming positive ions.
• Metallic Bonding: Strong electrostatic attraction between delocalized electrons and positive metal ions.
  • Not Ionic Bonding: Although similar, metallic bonding is distinct from ionic bonding.

Properties of Metals

• High Melting and Boiling Points: Strong metallic bonds require a lot of energy to break.
• Conductivity:
  • Heat and Electricity: Delocalized electrons can move, carrying electrical current and thermal energy.
• Malleability:
  • Bending and Shaping: Atoms can slide over each other.

Alloys

• Need for Alloys: Some metals like copper, gold, iron, and aluminum are too soft for practical use.
• Definition: An alloy is a mixture of metals.
• Hardness: Different atomic sizes distort layers in the alloy, preventing atoms from sliding easily.
  • Result: Alloys are generally harder than pure metals.

Study Resources

• Additional questions and practice can be found in the revision workbook available through the provided link.