Lesson 4: Lewis Structures & VSEPR Theory

Day 1:
What are the steps for drawing Lewis structures?
How do you represent single, double, and triple bonds in a Lewis structure?
What is resonance and how is it represented in Lewis structures?

Day 2:
What is the VSEPR theory and what is its purpose?
How do electron pairs arrange themselves around a central atom?
How do you predict molecular shapes and bond angles using VSEPR theory?

Day 3:
How does molecular shape affect molecular polarity?
What are polar and nonpolar molecules and how do they interact?

Lewis structure

VSEPR (Valence Shell Electron Pair Repulsion)

Electron domain (bonding/lone pairs)

Molecular geometry (e.g., linear, trigonal planar, tetrahedral)

Bond angle

Polarity

HS-PS1-1 Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms

These standardized tests often include questions that assess the understanding of Lewis structures and VSEPR theory. Students may be asked to:
Draw Lewis structures for various molecules.
Predict molecular shapes and bond angles using VSEPR theory.
Determine whether a molecule is polar or nonpolar.

Day 1: Lewis Structures
Description: This lesson focuses on drawing Lewis structures to represent molecules. Students will learn the rules for drawing Lewis structures and practice drawing them for various molecules, including those with single, double, and triple bonds, and those that exhibit resonance.
Purpose: To provide students with a visual representation of molecules and to help them understand the arrangement of electrons in molecules.
DOK Level: 2 (Understand), 3 (Apply)

Day 2: VSEPR Theory
Description: This lesson introduces the VSEPR theory, which is used to predict molecular shapes based on the arrangement of electron pairs around a central atom. Students will learn how to apply the VSEPR theory to predict molecular shapes and bond angles.
Purpose: To enable students to predict the three-dimensional shapes of molecules, which is crucial for understanding their properties and reactivity.
DOK Level: 2 (Understand), 3 (Apply)

Day 3: Molecular Shape and Polarity
Description: This lesson connects molecular shape to molecular polarity. Students will learn how to determine whether a molecule is polar or nonpolar based on its shape and the electronegativity differences between the atoms.
Purpose: To help students understand the relationship between molecular shape and molecular properties, particularly polarity, which influences intermolecular forces and macroscopic properties.
DOK Level: 3 (Apply)

Day 1:
Discuss the importance of Lewis structures in understanding chemical reactions and the behavior of molecules.
Day 2:
Relate molecular shapes to the function of biological molecules like enzymes and proteins.
Day 3:
Connect molecular polarity to the properties of water and its importance for life.
Discuss the role of molecular polarity in various applications, such as detergents and pharmaceuticals.

Day 1:
Students may struggle with drawing Lewis structures correctly, especially for molecules with multiple bonds or resonance.
Students may not understand the concept of formal charge and its role in choosing the best Lewis structure.

Day 2:
Students may have difficulty visualizing three-dimensional shapes from two-dimensional Lewis structures.
Students may confuse electron domain geometry with molecular geometry.

Day 3:
Students may not fully grasp the relationship between bond polarity and molecular polarity.
Students may struggle with determining whether a molecule is polar or nonpolar based on its shape.

Support:
Provide step-by-step guides for drawing Lewis structures and applying VSEPR theory.
Use molecular models or simulations to help students visualize molecular shapes.
Provide partially completed Lewis structures or molecular shapes for students to finish.
Offer extra practice with simpler examples before moving on to more complex ones.

Challenge:
Have students research and present on the applications of VSEPR theory in predicting the properties of novel molecules.
Introduce more complex molecular geometries, such as those found in coordination compounds.
Explore the relationship between molecular polarity and intermolecular forces.

Formative:

Class discussions and questioning.

Worksheet practice.

Whiteboard activities.

Observation of student participation in activities.

Summative:

End-of-lesson quizzes.

Periodic tables

Textbook

Whiteboard or projector

Computer with internet access for simulations and videos

Molecular model kits

Lewis structure worksheets

VSEPR Molecular Shapes

Worksheets and practice problems