Ionic Bonding and Lattice Structure
Formation of Ions and Ionic Bonds · The Giant Ionic Lattice
IB Chemistry topic guide
Structure 2: Bonding and Structure
Structure 2: Bonding and Structure is a core part of IB Chemistry. This guide connects the syllabus ideas behind Ionic Bonding and Lattice Structure, Properties of Ionic Compounds, Covalent Bonding, Bond Polarity and Intermolecular Forces, Metallic Bonding and 2 more units, shows how they appear in worked problems, and points you to the formulas and full lessons needed for exam revision.
What you will learn
Structure 2: Bonding and Structure syllabus outline
The units below follow the structure used in the full Study to Learn course. Use the outline to identify exactly which idea needs attention, then work through the public example before continuing to the complete lesson path.
Properties of Ionic Compounds
Melting Point, Conductivity, and Solubility · Lattice Enthalpy and Ionic Bond Strength
Covalent Bonding
Covalent Bonds and Lewis Structures · VSEPR Theory and Molecular Shapes
Bond Polarity and Intermolecular Forces
Electronegativity and Bond Polarity · Intermolecular Forces: London, Dipole–Dipole, and Hydrogen Bonding
Metallic Bonding
The Electron Sea Model · Trends in Metallic Bond Strength
Alloys and Conductivity
Alloys: Modifying Metal Properties · Conductivity and the Effect of Alloying
From Models to Materials
Giant Covalent Structures: Diamond, Graphite, and SiO₂ · Comparing Material Properties Across Bonding Types
Free worked preview
Formation of Ions and Ionic Bonds
This complete preview comes from the Ionic Bonding and Lattice Structure unit. It introduces the core language, shows the method in context, and gives you a real example of the lesson quality before you create an account.
From Atoms to Ions
Table salt — sodium chloride — is held together by one of the strongest and most important types of bonding in chemistry. This lesson introduces ionic bonding as the electrostatic attraction between oppositely charged ions formed by electron transfer between metals and non-metals. After this lesson, you will be able to predict ionic charges from an element’s group, write correct ionic formulas by balancing charges, and understand why ionic compounds are not made of discrete molecules but of giant repeating lattices.
Ionic bonding results from the electrostatic attraction between oppositely charged ions. Metals lose electrons to form cations (positive); non-metals gain electrons to form anions (negative).
Predicting Ionic Charges
- Group 1: lose 1e⁻ → 1+ (Na⁺, K⁺)
- Group 2: lose 2e⁻ → 2+ (Mg²⁺, Ca²⁺)
- Group 13: lose 3e⁻ → 3+ (Al³⁺)
- Group 16: gain 2e⁻ → 2− (O²⁻, S²⁻)
- Group 17: gain 1e⁻ → 1− (F⁻, Cl⁻)
- Transition metals form multiple cations (Fe²⁺ / Fe³⁺, Cu⁺ / Cu²⁺)
Writing Ionic Formulas
Total positive charge must equal total negative charge. The formula gives the simplest whole-number ratio. E.g. Mg²⁺ + Cl⁻ → MgCl₂ (1:2); Al³⁺ + O²⁻ → Al₂O₃ (2:3, since 2×(+3)=6+ balances 3×(−2)=6−).
Worked Example
Predict the formula of the ionic compound formed between aluminium (Group 13) and sulfur (Group 16).
- Al is in Group 13 → loses 3e⁻ → Al³⁺
- S is in Group 16 → gains 2e⁻ → S²⁻
- Balance charges: the lowest common multiple of 3 and 2 is 6, so 2 Al³⁺ (2×3=6+) balances 3 S²⁻ (3×2=6−)
Formula: Al₂S₃
Common ErrorIonic compounds do NOT consist of individual “molecules.” The formula NaCl represents the ratio of ions in a giant lattice, not discrete NaCl molecules. There is no single NaCl molecule.
Reviewed by the Study to Learn editorial team · Updated 2026-08-04