pptx, 2.87 MB
pptx, 2.87 MB

This PowerPoint lesson introduces resonance structures and electron delocalisation, helping Higher Level IBDP Chemistry students understand why some molecules cannot be represented by a single Lewis structure. Designed specifically for first assessment 2025, it builds the conceptual depth and exam precision required for HL organic and structural chemistry.

Resonance occurs when two or more valid Lewis structures can be drawn for the same arrangement of atoms but with different distributions of electrons. The real species is not switching between these structures; instead, it exists as a resonance hybrid with delocalised electrons and intermediate bond properties. This lesson develops this definition carefully and links it directly to experimental evidence.

The PowerPoint uses ozone (O₃) as a central case study, drawing on bond energy and bond length data to show why its O–O bonds are identical and intermediate between single and double bonds. Students are guided through how resonance explains these observations, including the use of double-headed arrows, dashed-bond hybrid representations, and the concept of bond order.

Further examples include the carbonate ion (CO₃²⁻), nitrate ion (NO₃⁻) and carbonite ion (CO₂²⁻), allowing students to practise identifying resonance, counting valid structures, and calculating fractional bond orders. Common misconceptions are explicitly addressed, particularly the idea that molecules “flip” between resonance forms.

The lesson includes starter activities, clearly defined learning outcomes, worked examples, practice questions, and answers that reflect IB command terms and markscheme expectations. It is suitable for classroom teaching, guided practice, or HL revision.

File type included: PowerPoint (.pptx)
Last updated: January 2026 – explanations refined, misconceptions addressed, and HL scope checked against the 2025 syllabus.

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BUNDLE S2.2 The Covalent Model HL Only Content (IBDP Chemistry)

This comprehensive bundle of PowerPoints covers the Higher Level content of Topic 2.2 The Covalent Model for IBDP Chemistry (first examination 2025). It develops deep conceptual understanding of resonance, benzene, expanded octets, formal charge, sigma and pi bonding, and hybridisation in a structured, exam-focused sequence. The covalent model explains how atoms share electrons to form molecules, and at HL it extends beyond simple Lewis structures to include delocalisation, orbital overlap and electron-domain analysis. This bundle is designed to build that progression logically — from resonance structures through to hybridisation and aromatic stability — ensuring students can connect Lewis formulas, VSEPR theory, bond order, formal charge and orbital theory. Included lessons: • Resonance Structures – electron delocalisation, bond order, ozone, carbonate, nitrate and resonance hybrids • Benzene – historical models, bond length evidence, hydrogenation data, resonance energy and aromatic stability • Expanded Octets & VSEPR – five and six electron domains, trigonal bipyramidal, T-shaped, octahedral, square planar • Formal Charge – selecting preferred Lewis structures and evaluating charge distribution • Sigma and Pi Bonds – orbital overlap, bond strength, restricted rotation, delocalised π systems • Hybridisation – sp, sp², sp³ bonding, excitation, molecular geometry and benzene delocalisation Throughout the bundle, students analyse physical and chemical evidence, compare alternative structures, and apply exam-style reasoning. Clear worked examples, mini-whiteboard tasks, structured explanations and practice questions are included in each lesson. This resource is ideal for teaching, consolidation or HL revision and aligns fully with the 2025 IB Chemistry syllabus. File type included: Multiple PowerPoint files (.pptx) Last updated: January 2026 – sequencing refined and cross-links between resonance, hybridisation and benzene strengthened for conceptual clarity.

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