Unit Overview
Chemical bonding
CIE A-Level ChemistryΒ· 5 min read π n/a
1. Unit at a glance
This unit builds from knowledge of individual atomic structure to how atoms interact to form stable compounds and bulk materials. We progress from the electrostatic bonding of ionic compounds, to shared-electron covalent and coordinate bonding, then the electron-sea model of metallic bonding. After mastering the core bonding types, we apply VSEPR theory to predict the shapes of simple molecules and ions, before connecting all prior concepts to explain how bonding type determines observable physical properties of substances.
This unit is split into 5 core sub-topics that progress from basic bonding definitions to applied property relationships:
Ionic bonding
Learn how ionic bonds form between oppositely charged ions and the structure of ionic lattices.
β β β± 8 min
Covalent and coordinate bonding
Explore shared-electron covalent bonds, bond energy/length, and the special case of dative coordinate bonding.
β β β± 10 min
Metallic bonding
Understand the electron sea model of metallic bonding and how it explains core metallic properties.
β β± 6 min
Shapes of molecules and ions
Apply VSEPR theory to predict bond angles and shapes of simple molecules and polyatomic ions.
β β β β± 12 min
Bonding and physical properties
Relate bonding type and structure to melting point, electrical conductivity, and solubility trends.
β β β β± 10 min
2. Common Pitfalls
Wrong move:
Confusing coordinate covalent bonds with ionic bonds
Why:
Coordinate bonds still involve shared electron pairs, even though one atom donates both electrons
Correct move:
Classify coordinate bonds as a sub-type of covalent bonding, not ionic bonding
Wrong move:
Ignoring the effect of lone pair repulsion on bond angles in VSEPR
Why:
Lone pairs repel more strongly than bonding pairs, leading to smaller bond angles than predicted from basic geometry
Correct move:
Always order repulsion strength: lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair
Wrong move:
Assuming all covalent compounds have low melting points
Why:
Giant covalent lattices have strong covalent bonds throughout the entire structure, requiring large amounts of energy to break
Correct move:
Distinguish between simple molecular covalent structures (low melting point) and giant covalent structures (high melting point)
3. Quick Reference Cheatsheet
Concept | Key Unit Summary |
|---|---|
Ionic bonding | Electrostatic attraction between oppositely charged ions in a giant ionic lattice |
Covalent bonding | Electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms |
Coordinate bonding | Covalent bond where both electrons in the shared pair are donated by a single atom |
VSEPR repulsion order | Lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair repulsion |
Metallic bonding | Electrostatic attraction between positive metal cations and a delocalised sea of electrons |
Melting point trend | Giant structures (ionic, metallic, covalent) have much higher melting points than simple molecular structures |
What's Next
Begin your study of this unit with the first sub-topic covering ionic bonding, the first core bonding type in this unit. Once you complete all 5 sub-topics in Chemical Bonding, you can move on to the next unit of the CIE 9701 syllabus covering states of matter.