Activity 01
Pair Sort: Lewis Species Cards
Provide cards with molecules and ions like BF3, NH3, AlCl3, H2O. Pairs sort into Lewis acids, bases, both, or neither, then justify with electron pair roles. Follow with class share-out of tricky cases.
Differentiate between Bronsted-Lowry and Lewis definitions of acids and bases.
Facilitation TipDuring Pair Sort: Lewis Species Cards, circulate and listen for pairs to justify their classifications, stepping in only when their reasoning relies on Bronsted assumptions rather than electron pairs.
What to look forPresent students with a series of reactions, some involving proton transfer and some not. Ask them to identify the Lewis acid and Lewis base in each reaction and explain their reasoning based on electron pair movement. For example: BF3 + NH3 -> F3B-NH3. Which is the Lewis acid, and why?
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Activity 02
Molecular Kit Demo: Adduct Formation
Demonstrate BF3 + NH3 using ball-and-stick kits; students in small groups replicate and draw electron flow. Predict products for CO + Ni then build models. Discuss changes in geometry.
Identify Lewis acids and bases in reactions that do not involve proton transfer.
Facilitation TipIn Molecular Kit Demo: Adduct Formation, ask students to describe the electron movement as they assemble the adduct, focusing their attention on the vacant orbital and lone pair interaction.
What to look forFacilitate a class discussion comparing the Bronsted-Lowry and Lewis models. Ask students: 'In what types of chemical reactions is the Lewis model more useful than the Bronsted-Lowry model? Provide a specific example of a reaction where only the Lewis model can adequately explain the bonding.'
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Activity 03
Relay Prediction: Reaction Chains
Teams line up; first student draws a Lewis acid-base reaction like AlCl3 + Cl-, passes to next for product. Include complex ions. Correct as a class and vote on best explanations.
Analyze the utility of the Lewis model in explaining complex ion formation.
Facilitation TipDuring Relay Prediction: Reaction Chains, challenge groups to explain their predictions aloud before moving to the next reaction to ensure all voices contribute to the reasoning process.
What to look forProvide students with the formula for a metal complex, such as [Cu(NH3)4]2+. Ask them to identify the Lewis acid (the metal ion) and the Lewis base (the ligand) and explain how the bond forms between them using the Lewis model.
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Activity 04
Digital Sim: Coordination Explorer
Use PhET or MolView for students to pair metals with ligands individually, note electron acceptance. Share screens in pairs to compare stability predictions.
Differentiate between Bronsted-Lowry and Lewis definitions of acids and bases.
Facilitation TipIn Digital Sim: Coordination Explorer, pause the simulation at key steps to ask students to predict what will happen next based on electron pair availability.
What to look forPresent students with a series of reactions, some involving proton transfer and some not. Ask them to identify the Lewis acid and Lewis base in each reaction and explain their reasoning based on electron pair movement. For example: BF3 + NH3 -> F3B-NH3. Which is the Lewis acid, and why?
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Generate Complete Lesson→A few notes on teaching this unit
Start by explicitly contrasting Lewis and Bronsted-Lowry models using side-by-side examples, as research shows this direct comparison reduces confusion. Avoid over-relying on proton-based examples when teaching Lewis acids, since this reinforces the misconception that all acids must contain hydrogen. Use transition metal chemistry early to highlight the breadth of the Lewis model and build relevance for students interested in inorganic or materials science.
By the end of these activities, students will confidently identify Lewis acids and bases in reactions without protons, explain adduct formation using electron pair donation, and compare the Lewis model to Bronsted-Lowry in complex ion formation. They will articulate why the Lewis model is essential for understanding coordination chemistry.
Watch Out for These Misconceptions
During Pair Sort: Lewis Species Cards, watch for students who incorrectly classify BF3 as a Bronsted acid because it contains boron, or NH3 as a Bronsted base due to its nitrogen.
During Pair Sort: Lewis Species Cards, redirect students by asking them to focus on the presence of a vacant orbital in BF3 and a lone pair on NH3, using the card descriptions to guide their classification.
During Molecular Kit Demo: Adduct Formation, watch for students who assume the bond forms because of a proton transfer, especially when using NH3.
During Molecular Kit Demo: Adduct Formation, have students physically point to the electron pair donated by NH3 and the vacant orbital on BF3, reinforcing the electron pair mechanism with the molecular model.
During Relay Prediction: Reaction Chains, watch for students who default to Bronsted terminology when discussing reactions without protons, such as metal-ligand complexes.
During Relay Prediction: Reaction Chains, stop the group and ask them to restate their explanation using only Lewis terminology, emphasizing electron pair donation and acceptance.
Methods used in this brief