UC Irvine FOCUS! 5 E Lesson Plan

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1 UC Irvine FOCUS! 5 E Lesson Plan Title: Covalent and Ionic Bonding Lewis Structures Lab Grade Level and Course: 8 th grade Physical Science, 10 th and 11 th Chemistry Materials: Special deck of 24 element cards Colored Games Chips (electrons) Instructional Resources Used: (concept maps, websites, think-pair-share, video clips, random selection of students etc.) Graphic Organizers : Graphic organizers are a means of introducing and assessing concepts in a manner that encourages meaningful learning. Graphic organizers are diagrams or maps that show the relationship between new and existing concepts, thereby facilitating integration of new and familiar ideas. They require minimal language and are therefore helpful tools when teaching science to English language learners. Using a Venn diagram, have students compare and contrast ionic and covalent bonds. Cooperative learning Many of the activities in this book employ group work and cooperative learning. Cooperative activities provide opportunities for students to exchange, write, and present ideas. Have students work in groups of 3s or 4s to construct Lewis dot diagrams structures models using 24 element cards and colored games chips (electrons). California State Standards: Structure of Matter (Middle School) Structure of Matter 3b. Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements. Chemical Bonds (High School) 2. Biological, chemical, and physical properties of matter result from the ability of atoms to form bonds from electrostatic forces between electrons and protons and between atoms and molecules. As a basis for understanding this concept: a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds. e. Students know how to draw Lewis dot structures Common Core State Standards: (written out) Lesson Objectives: Describe the properties of ionic bonds Describe the properties of covalent bonds Interpret and draw Lewis dot diagrams for individual atoms

2 Differentiation Strategies to meet the needs of diverse learners: English Learners: o Model laboratory activities Demonstrate activities in front of class to ensure that English language learners can see the procedures before engaging in an activity. Model several simple examples of Lewis dot structures. Within their lab groups, students can also benefit from the assistance of a peer tutor. Special Education: o The strategies outlined for English Learners are also appropriate for Special Education students as well. o Place students into mixed ability groupings to allow for peer tutoring and to promote deeper understanding of the content. GATE: o Alternative Assessment: Searching for the perfect artificial sweetenergreat taste with no calories has been the focus of chemical research for some time. Molecules such as sucralose, aspartamine, and saccharin owe their sweetness to their size and shape. One theory holds that any sweetener must have three sites that fit into the proper taste buds on the tongue. This theory is appropriately known as the triangle theory. Have students to research artificial sweeteners to develop a model to show how the triangle theory operates. ENGAGE Describe how the teacher will capture the students interest. After viewing a PowerPoint on Covalent and Ionic Bonds (sorry, but a powerpoint really isn t all that engaging to kids. Can you do something else? The powerpoint should be part of the main lesson). Using a Venn diagrams, have students compare and contrast the difference properties of ionic and covalent bonds. What kind of questions should the students ask themselves after the engagement? Why are elements more stable as ions then they are as atoms? By gaining or losing electrons the atoms of elements achieve a noble- gas electron configuration. 2. Describe the difference between an ionic or covalent bond. Ionic bonds depend on electrostatic attraction between ions. Covalent bonds depend on electrostatic attraction between shared electrons and nuclei of combining atoms.

3 EXPLORE Describe the hands-on laboratory activity that the students will be doing. Students will use a Using a shorthand method to represent how atoms form covalent or ionic, according to the following rules: Lewis dot diagrams use dots arranged around the atomic symbol to represent the electrons in the outermost energy level of an atom. Single bonds are represented by a pair of dots or one line between atoms. Double bonds are represented by two pairs of dots or two lines between atoms. Triple bonds are represented by three pairs of dots or three lines between atoms. List the big idea conceptual questions that the teacher will ask to focus the student exploration. What information about a molecule does its Lewis Structure provide? What information is neither shown nor implied in the Lewis structure? EXPLAIN What is the big idea concept that students should have internalized from doing the exploration? The model of the atom and of covalent and ionic bonding emphasizes the attractions between bonding atoms. Only the valence electrons are involved in these two types of bonding. By looking at the molecular formulas, this fact is not obvious. However, by using molecular diagrams called Lewis structures, this fact is easily deduced. The purpose of Lewis structures is to provide a simple way for chemists to represent molecules that allows reasonable predictions to be made about the structure and properties of the actual molecules. Remember to apply the octet rule. List the higher order questions that the teacher will ask to solicit student explanations for their laboratory outcomes, and justify their explanations. There are several exceptions to the octet rule. 1. Based on its electron configuration, explain why hydrogen can only have two valence electrons around it when it bonds to other atoms. What is the maximum number of bonds hydrogen will form? 2. Many elements in the third row and beyond in the periodic table may form more than four bonds and thus appear to have expanded octets. Phosphorus and sulfur, for example, may form five and six covalent bonds, respectively. Count up the total number of valence electrons in PCl5 draw its Lewis structure. How many valence electrons are counted toward the

4 central P atom? EXTEND Explain how students will develop a more sophisticated understanding of the concept: o Use the following terms to describe the molecular geometry for each model on your data table: Linear, trigonal planar, bent, tetrahedral, pyramidal, octahedral, square pyramidal, and square planar. ( Hint: Molecular geometry describes the physical arrangement of the atoms, not the electron pairs.) This is probably more of an extension not a power standard for grade 8. How is this knowledge applied in our daily lives? o Most common adhesives are sticky substances that you can use to bind two surfaces together. Adhesive is a liquid until the surfaces are in position. Then the adhesive sets into solid. Adhesion can work in three ways: Molecules of the polymer may fill crevices in the surfaces being connected, the molecules may also become attracted by intermolecular forces, or they may react by forming covalent bonds. EVALUATE How will the student demonstrate their new understanding and/or skill? Using the guidelines to formulate Lewis structures, students will construct skeleton structure molecules joining them by electrons which will results in single, double, or triple bonds. What is the learning product for the lesson? Students will complete Data Table A Showing the valence electrons and Lewis Structure for each molecule. Background Knowledge for the Teacher: The word combining implies bonding. Understanding the concepts of ionic and covalent bonding helps explain why some elements combine to form compounds and some do not. Covalent bonds are defined as the net attractive forces between nonmetal atoms that share one, tow, or three pairs of electrons. In general, only the valence electrons, those in the highest energy levels that are farthest away from the nucleus, are available for bonding. The number of valence electrons influences the number of bonds that an atom will form. Sources: Flinn ChemTopic Labs Chemical Bonding Volume 5, Science Framework For California Public Schools, for Kindergarten through Grade 12 Student pages are attached.

5 Lesson Objectives: Covalent and Ionic Bonding Lewis Structures Lab Describe the properties of ionic bonds Describe the properties of covalent bonds Interpret and draw Lewis dot diagrams for individual atoms Materials: Special deck of 24 element cards Colored Games Chips (electrons) Procedure: 1. Use the following guidelines to assemble a Lewis Structure for each molecule or ion. Note: Keep in mind the exception to the octet rule. What do you mean, the exception? Do you mean for them to apply it? 1. Select the elements cards colored games chips (electrons) for each molecule. Use the color key to match the correct element cards to the colored games chips (electrons). 2. Count the number of valence electrons supplied by each atom in the formulas. Determine the total number of valence electrons and record in number in Data Table A. In the case of polyatomic ions, add one electron for each unit of negative charge or subtract one electron for each unit of position charge to determine the total number of valence electrons 3. The atom with the most unshared paired of electrons is the central atom. For example, carbon is often placed in the center of the molecule and hydrogen is never placed as a center atom. The least electronegative atom is usually the central atom. 4. Arrange the other atoms around the central atom. Distribute the electron game chips so that each atom, except for hydrogen, beryllium, and boron, satisfies the octet rule. 5. Place the electrons outside atoms. Use remaining electrons to satisfy the octets for each of the outside atoms. If you run out of electrons at this point, the skeleton structure was wrong. Go back to step Place all remaining electrons on the central atom. If there are more than 8 electrons on the central atom, you counted the number of valence electrons incorrectly. Go back to step 2 7. If the octet on the central atom is not complete, try sharing lone pairs (unpaired shared) of outside atoms to form double or triple bonds.

6 8. Draw a sketch of the molecule of the Lewis Structure in the space provided on the Data Table A 9. Complete the last two spaces on your Data Table by making up your own Lewis Structure following the rules listed above. Element Color electron Key Carbon-C Chlorine-Cl Silicon-Si Oxygen- O Boron Sulfur-S Hydrogen-H Fluorri ine--f Nitrogen Phosphorus-P Post Analysis Questions: 1. Write the Lewis dot structure for each of the following atoms: Hydrogen, boron, nitrogen, silicon, sulfur, and bromine. 2. What information about a molecule does its Lewis Structure provide? 3. What information is neither shown nor implied in the Lewis structure? 4. How many electrons are shared by two atoms that form a triple bond? 5. Which electrons do a Lewis structure show? Give an example. 6. Do you always follow the octet rule when drawing a Lewis structure? Explain

7 Covalent and Ionic Bonding Lewis Structures Lab Data Table A Name Molecular Formula Valence Electrons Lewis Structure Boron Trichloride BCl3 Methane CH4 Ethylene C2H4 Ammonia NH3 Ammonium ion NH4 + Hydrogen Sulfide H2S Sulfur Trioxide SO3 Carbon Tetrachloride CCl4 Formaldehyde H2CO

8 Carbon Disulfide CS2 Hydrogen Cyanide HCN Sulfate Ion SO4 2-

9 Red H Red H Red Red H H Orange Orange B N Orange Orange

10 P Si Blue Blue O O Blue O Orange S Green Green

11 Cl Cl Green Green Cl Cl Purple C Blue O Purple Purple

12 C C Yellllow Yellllow F F Yellllow Yellllow F F