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In this unit, students learn why atoms form bonds and what holds atoms and molecules together. Material covered includes Ionic Bonding, Covalent Bonding, Intermolecular forces, Metallic Bonding, Physical properties, shapes of molecules and ions, hybridization and delocalization of electrons.

Essential idea

Atomic structure is the unifying concept in Chemistry.

Learning Targets

Topic 4: Bonding (13.5 hours)

4.1 Ionic bonding and structure


Unique Individuals - Nobel Laureate Sir Harold Kroto

  • Describe the formation and nature of ionic bonds
  • Describe the lattice structure of ionic compounds
  • Describe and explain physical properties of ionic compounds (volatility, electrical conductivity and solubility) in terms of structure.

4.2 Covalent bonding

  • Describe the covalent bond as the electrostatic attraction between a pair of electrons and positively charged nuclei
  • Describe the formation of single/double/triple covalent bonds
  • Understand the relationship between bond length and strength and explain in terms of number of shared electron pairs
  • Deduce the bond polarity from electronegativity differences

4.3 Covalent structures

  • Deduce the Lewis (electron dot) structures of molecules and ions for up to four electron pairs on each atom
  • Predict the shape and bond angles for species with four, three and two electron domains negative using the valence shell electron pair repulsion theory (VSEPR)
  • Predict whether or not a molecule is polar from its molecular geometry and bond polarities
  • Deduction/explanation of resonance structures
  • Describe and compare the structure and bonding in the allotropes of carbon (diamond, graphite graphene and C60 fullerene)
  • Describe the structure of and bonding in silicon and silicon dioxide
  • Describe the formation of dative covalent bonds

4.3 Intermolecular forces

  • Describe the types of intermolecular forces London/dispersion forces, diole-dipole forces and hydrogen-bonding
  • Describe the relative strengths of these intermolecular forces
  • Describe and explain how intermolecular forces affect the physical properties of substances

4.4 Metallic bonding

  • 4.4.1 Describe the metallic bond as the electrostatic attraction between a lattice of positive ions and delocalized electrons
  • . Understand the factors affecting the strength of the metallic bond
  • Explain the electrical conductivity and malleability of metals
  • Explanation of properties of alloys in terms of non-directional bonding

Topic 14: Bonding (7 hours) - HL Students Only

14.1 Further aspects of covalent bonding and structure

  • Describe and explain the formation of σ and π bonds
  • Describe and explain the formation of σ and π bonds
  • Use of the concept of Formal Charge (FC) to make predictions as to the most favoured Lewis structure
  • Exceptions to the octet rule
  • An understanding of delocalisation and its effect on stability
  • Description of resonance structures using two (or more Lewis structures

14.2 Hybridization

  • Explain hybridization in terms of the mixing of atomic orbitals to form new orbitals for bonding
  • Identify and explain the relationships between Lewis structures, molecular shapes and types of hybridization (sp, sp2 and sp3)

The detailed curriculum can be consulted here.

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