Chapter 6: Metallic Bonding

Metallic Bonding Overview

• Definition: Metallic bonding is the attraction between metal atoms and the surrounding sea of electrons.
• Comparison: This type of bonding differs from ionic, molecular, or covalent-network compounds.
• Properties: The unique characteristics of metallic bonding lead to the following properties of metals:
  • Excellent electrical conductivity in solid state
  • High thermal conductivity
  • Malleability (ability to be hammered into thin sheets)
  • Ductility (ability to be drawn into wires)
  • Shiny appearance (luster)

Electron-Sea Model

• Delocalization of Electrons: In metals, vacant orbitals in the outer energy levels of atoms overlap, allowing outer electrons to roam freely throughout the metal.
• Sea of Electrons: These delocalized electrons create a 'sea' around positively charged metal nuclei, providing structural stability and contributing to metallic properties.

Conductivity

• Electrical Conductivity: The mobility of electrons facilitates electrical conduction, as free electrons can move swiftly throughout the metal.
• Thermal Conductivity: Similar to electrical conductivity, mobile electrons also transfer heat effectively, making metals good thermal conductors.

Malleability and Ductility

• Malleability: Metals can be hammered or beaten into thin sheets due to the ability of layers of atoms to slide over one another without breaking the metallic bond.
• Ductility: Metals can be drawn, pulled, or extruded into wires as the metallic bonds allow the structure to deform rather than fracture under stress.

Shiny Appearance

• Luster: Metals are strong absorbers and reflectors of light. The reflected light produces a characteristic shiny appearance or metallic luster.

Factors Affecting Metallic Bond Strength

• Nuclear Charge: The strength of metallic bonds increases with higher nuclear charge of the metal atoms.
• Number of Electrons: A greater number of electrons in the electron sea contributes to stronger metallic bonding.

Enthalpy of Vaporization

• Definition: Enthalpy of vaporization is the amount of energy required to vaporize a substance at constant pressure. This property varies among different metals according to their bonding strength.