PMT Lecture Notes: Bonding, Structure, and Properties

2.1 Bonding, Structure, and Properties

Overview

• Focuses on different types of bonding in chemistry, including ionic, covalent, and metallic.
• Examines how bonding influences the structure and properties of substances.

Types of Bonding

Ionic Bonding

• Definition: Transfer of electrons from one atom to another, leading to the formation of ions.
• Characteristics:
  • Formed between metals and non-metals.
  • High melting and boiling points due to strong electrostatic forces between ions.
  • Generally soluble in water and conduct electricity when molten or in solution.

Covalent Bonding

• Definition: Sharing of electron pairs between atoms.
• Characteristics:
  • Occurs between non-metal atoms.
  • Can be single, double, or triple bonds.
  • Low melting and boiling points compared to ionic compounds.
  • Most do not conduct electricity as they have no free ions or electrons.

Metallic Bonding

• Definition: Bonding between metal atoms where electrons are free to move.
• Characteristics:
  • Delocalized electrons across a lattice of positive ions.
  • Conduct electricity and heat due to the movement of electrons.
  • Malleable and ductile as atoms can slide over each other while maintaining the metallic bond.

Influence on Structure and Properties

Ionic Compounds

• Structure: Lattice structure composed of alternating positive and negative ions.
• Properties:
  • Brittle due to the rigid lattice structure.
  • Conductivity in liquid state or when dissolved.

Covalent Substances

• Structure: Can be simple molecules or giant covalent structures (e.g., diamond and graphite).
• Properties:
  • Simple molecular substances have low melting and boiling points.
  • Giant covalent structures like diamond have high melting points.
  • Graphite conducts electricity due to free-moving electrons.

Metals

• Structure: Layers of atoms in a lattice structure.
• Properties:
  • High melting and boiling points.
  • Good conductors of heat and electricity.
  • Malleability and ductility due to the ability of atoms to slide past one another.

Key Concepts

• Electronegativity: Affects the type of bonding that occurs.
• Polarity: In polar covalent bonds, electrons are shared unequally.
• Intermolecular Forces: Include Van der Waals forces, dipole-dipole interactions, and hydrogen bonding, significantly influencing the properties of molecules.

Summary

• Different types of chemical bonds result in varied structures and properties.
• Understanding bonding is essential for explaining the behavior and characteristics of different substances in chemistry.