Free Science Lessons: Metal and Alloy Properties

Overview

• Focus on metallic bonding, properties of pure metals, and alloys.
• Examples: Pure gold bar and a guitar string (alloy).

Metallic Bonding

• Metal Stability: Atoms achieve a stable state via a full outer energy level.
  • Metal + Non-metal = Ionic Bonding
  • Non-metal + Non-metal = Covalent Bonding
• Structure in Metals:
  • Metals consist of a giant structure of atoms in regular layers.
  • Outer electrons are delocalized (free to move across the whole structure).
  • Delocalized Electrons: Referred to as a "sea of delocalized electrons."
• Metallic Bonds:
  • Positive metal ions are created as metal atoms lose their outer electrons.
  • Strong electrostatic attraction exists between delocalized electrons and positive metal ions.
  • This is known as metallic bonding, which is strong.

Properties of Metals

• High Melting and Boiling Points:
  • Strong metallic bonds need a lot of energy to break.
• Conductivity:
  • Excellent conductors of heat and electricity due to the mobility of electrons.
  • Moving electrons carry electric current and thermal energy.
• Malleability:
  • Layers of atoms in metals can slide over each other, allowing metals to be bent and shaped.

Alloys

• Purpose: Make metals harder, as some pure metals (copper, gold, iron, aluminum) are too soft.
• Structure: Mixture of metals with different atom sizes.
  • Distorted layers make it difficult for layers to slide over each other.
• Result: Alloys are harder than pure metals.

Additional Resources

• Revision workbook and additional questions available through provided link.