pptx, 1.68 MB
pptx, 1.68 MB

This PowerPoint lesson introduces formal charge as a tool for evaluating Lewis structures, helping Higher Level IBDP Chemistry students determine the most stable electron arrangement. Designed for first assessment 2025, it develops the analytical skills required to justify preferred structures when multiple valid Lewis formulas exist.

Formal charge is a theoretical bookkeeping method used to compare the valence electrons of a free atom with the electrons assigned to it in a Lewis structure. This lesson clearly defines formal charge, provides the calculation formula, and shows how it is applied to individual atoms within molecules and polyatomic ions. Students learn how to select the preferred structure by minimising non-zero charges, reducing charge separation, and placing negative charges on more electronegative atoms.

Step-by-step examples include CO₂, H₃O⁺, ICl₄⁻ and N₂O, illustrating how formal charge distinguishes between alternative structures that all satisfy the octet rule. The lesson also explains how coordination (dative) bonds affect charge distribution and reinforces the need to check that the sum of formal charges equals the overall molecular or ionic charge.

Importantly, limitations of formal charge are discussed, including the fact that it does not directly account for electronegativity differences or experimental evidence. Students are encouraged to combine formal charge analysis with chemical reasoning and resonance concepts.

The PowerPoint includes starter activities, worked examples, structured calculation steps, and practice questions suitable for Higher Level teaching, consolidation or revision.

File type included: PowerPoint (.pptx)
Last updated: January 2026 – calculation steps clarified, additional worked examples included, and HL scope checked against the 2025 IB Chemistry 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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