Metals and Metallic Bonding

Properties of Metals

• Metals have free valence electrons, which enable good thermal and electrical conductivity.
• Metals readily lose their electrons to form positive ions.
• The metallic bond is held by electrostatic force between delocalized electrons and positive ions.

Definition of Delocalized Electrons

• Delocalized electrons are electrons that are not associated with a single atom or covalent bond in a molecule, ion, or solid metal.

Alloys

• Alloys are metallic materials formed by mixing two or more elements.
• Examples of alloys: Mild steel (Fe + C), Stainless steel (Fe + C + Cr + Mn).
• The roles of different elements in alloys:
  • C: improves strength.
  • Cr: improves corrosion resistance.

Ceramics

• Ceramics are inorganic, non-metallic crystalline compounds, usually oxides, Carbides, Nitrides, Borides, or Silicides.
• Examples of ceramics: SiO2, Al2O3, MgO, TiO2, BaO, SiC, Si3N4, TiB2, WSi2, MoSi2.

Classification of Ceramics

• There are two principal categories: application base system and composition base system.

Application Base Classification

• Traditional Ceramics:
  • Include pottery, china, porcelain products.
  • Utilize natural ceramic ores.
• Advanced Ceramics:
  • Include Alumina, magnesia, Carbides, Nitrides, Borides, Silicides.
  • Are synthetic materials with better mechanical properties.
  • Electronic ceramics fall into this category.

Note on Glasses

• Glasses are amorphous (non-crystalline) compounds with "short range" order of atoms.
• Some literature includes glasses in the same category as ceramics.

Test your knowledge on metals and metallic bonding, including the properties of metals, the role of valence electrons, and the formation of positive ions. Learn about the electrostatic force that holds metallic bonds together and the concept of delocalized electrons.