O Levels/IGCSE Chemistry Lesson Plan 8.3

Section	Details
Objective	– Describe Group VII halogens (chlorine, bromine, iodine) as diatomic non-metals.- Explain general trends down the group: (a) increasing density, (b) decreasing reactivity.- State the appearance of chlorine, bromine, and iodine at room temperature.
Activities	– Starter (5 mins): Show images or videos of chlorine, bromine, and iodine and ask: “What differences do you notice among these elements?”- Main (25 mins): 1. Explain the diatomic nature of halogens and their placement in Group VII. 2. Discuss trends in density (increasing down the group) and reactivity (decreasing down the group) with explanations based on atomic size and electron shielding. 3. Describe the physical states and colors of halogens at room temperature: chlorine (pale yellow-green gas), bromine (red-brown liquid), iodine (grey-black solid).- Plenary (10 mins): Students complete a table summarizing the physical properties and trends of chlorine, bromine, and iodine.
Resources	Images or videos of halogens, periodic table, worksheets.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write a paragraph explaining why iodine is a solid while chlorine is a gas at room temperature.
Assessment	Worksheet: Identify and explain trends in the physical properties of Group VII elements.
Past Paper Practice	IGCSE Chemistry 0620/41/M/J/20 Q5(c) – Physical properties of halogens.

Section	Details
Objective	Describe and explain the reactivity trend of Group VII elements, including the decreasing reactivity down the group.
Activities	– Starter (5 mins): Pose the question: “Why is fluorine the most reactive halogen while iodine is the least?”- Main (25 mins): 1. Discuss the concept of reactivity in terms of electron gain to complete the outer shell. 2. Explain how atomic size, electron shielding, and nuclear attraction decrease reactivity down the group. 3. Provide examples of reactions showing decreasing reactivity (e.g., chlorine reacting with hydrogen faster than iodine).- Plenary (10 mins): Students draw a diagram showing the atomic structure of chlorine, bromine, and iodine, highlighting factors affecting reactivity.
Resources	Diagrams of atomic structure, videos of halogen reactions, worksheets.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write a paragraph explaining why reactivity decreases as you go down Group VII.
Assessment	Worksheet: Compare and explain the reactivity of Group VII elements based on atomic structure.
Past Paper Practice	IGCSE Chemistry 0620/41/O/N/21 Q5(a) – Reactivity trends in halogens.

Section	Details
Objective	Describe and explain the displacement reactions of halogens with halide ions.
Activities	– Starter (5 mins): Ask: “What happens if you mix chlorine water with potassium iodide solution?”- Main (25 mins): 1. Define displacement reactions and explain them using reactivity trends. 2. Demonstrate displacement reactions (e.g., chlorine water + potassium iodide → iodine + potassium chloride). 3. Write ionic equations for the reactions and explain electron transfer.- Plenary (10 mins): Students summarize displacement reactions in a flowchart, showing which halogens displace which halides.
Resources	Solutions of halogens and halides, reaction setups, worksheets.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write ionic equations for the reaction of bromine water with potassium iodide and predict the product.
Assessment	Worksheet: Predict and explain displacement reactions of halogens with given halides.
Past Paper Practice	IGCSE Chemistry 0620/41/M/J/19 Q6(b) – Displacement reactions of halogens.

Section	Details
Objective	Predict the properties of other elements in Group VII, given information about the elements.
Activities	– Starter (5 mins): Ask: “What do you think astatine would look like and how would it behave?”- Main (25 mins): 1. Discuss how trends in Group VII can be used to predict properties of fluorine and astatine. 2. Predict physical properties (e.g., state, color, density) and chemical behavior (e.g., reactivity, displacement ability). 3. Compare predictions with data provided in tables or charts.- Plenary (10 mins): Students complete a table comparing the predicted and actual properties of fluorine and astatine.
Resources	Periodic table, data tables for Group VII elements, worksheets.
Time	40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary).
Homework	Write a short explanation of why astatine is less reactive than iodine and predict its physical state at room temperature.
Assessment	Worksheet: Predict the properties of fluorine, astatine, and other Group VII elements based on trends.
Past Paper Practice	IGCSE Chemistry 0620/41/O/N/20 Q5(b) – Predicting properties of Group VII elements.

Physical Properties:
- Halogens are diatomic non-metals.
- Chlorine: Pale yellow-green gas, bromine: Red-brown liquid, iodine: Grey-black solid.
- Density increases down the group.
Reactivity:
- Reactivity decreases down the group due to increasing atomic size, electron shielding, and reduced nuclear attraction.
Displacement Reactions:
- More reactive halogens displace less reactive halides in solutions (e.g., Cl2+2I−→2Cl−+I2\text{Cl}_2 + 2\text{I}^- → 2\text{Cl}^- + \text{I}_2).
Trends and Predictions:
- Trends in physical and chemical properties allow predictions for unknown elements (e.g., fluorine, astatine).

Use hands-on experiments for displacement reactions to engage students.
Relate the concepts to real-world examples, such as halogens in disinfectants and bleach.
Provide ample practice with past paper questions to reinforce learning.