Creating Models of Ionic and Covalent Bonds

Description:

In this lesson, students will work in pairs to investigate two particluar elements and create a model which demonstrates either an ionic or covalent electronic bond between the two elements.

Subject:

Science and Technology

Duration:

200 min

Grade Levels:

6-8

Standards: 

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Resources: 

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Details

Context:

This lesson will expand upon the student's previous knowledge of the composition of an atom (i.e., electrons, protons, and neutrons), by showing how atoms can form bonds with one another to form molecules.  Students will also connect elements from the periodic table to the real world by listing real world materials which contain their particular element. 

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Objectives:

Through this lesson, students will gain a better understanding of the ways atoms bond together to form molecules and identify real world applications of specific elements.  Students will use cooperative learning, independent research, technology-based research and applications, and artistic creativty to assist in the completion of their projects.

Students will:

• Review the functions and locations of the parts of an atom and how molecules are formed; define related terminology; discuss what scientists have learned from studying and experimenting with atoms and molecules.
• Investigate various elements of the periodic table and identify groups of elements that have similar properties, including highly reactive metals, less-reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon).  Students will research an element and produce a report which includes the element’s atomic weight, atomic number, “real-world use”, position on the periodic table, and classification as a metal and nonmetal.
• Examine how new images of electronic bonds might impact the future study of science by reading and discussing "Glue of Molecular Existence Is Finally Unveiled."
• Define and illustrate metal-to-metal, ionic, and covalent bonds.
• Understand, through teacher demonstration, how to use materials given to them to create models of electronic bonds.
• Model, using given materials, ionic and covalent bonds.  

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Student Assessments:

Students will be evaluated formatively and summatively.  Formative evaluations will consist of submitted seatwork: definitions of the parts of electrons and molecules and written explanations of how ionic and covalent bonds work.  Students will also be evaluated formatively by observing their responses to teacher-posed questions and during their approach towards completing the element report and bonding model.

A formal assessment will occur through the submittal of a word-processed advertisement of their element, the construction of a model demonstrating ionic or covalent bonds, and the oral presentation.  See attached rubric for scoring guidelines.

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Connections:

This lesson connects to Language Arts, Math, and Technology interdisciplines in the following ways: 

Language Arts 
-The students will prepare a word-processed advertisement for his or her particular element.  The report will include important facts about the element and use advertising techniques to "sell" it as an important element.

Mathematics- Students will use math skills to determine the number of electrons that are lost, gained, or shared by the bonding atoms.

Technology- Students will use computers to conduct internet research and produce a word-processed document.

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Materials and Technology:

-student journals
-pens/pencils
-paper
-classroom blackboard
-copies of "Glue of Molecular Existence Is Finally Unveiled" (one per student)
-periodic table of the elements
-chemistry book to use as reference
-one paper or plastic bag per pair of students, each containing the following items (create an additional bag so you can model the activity): two large gumdrops (different colors); fourteen each of two different colors of small gumdrops (total 28 small gumdrops); bamboo or wooden skewers broken into the following sizes: four one inch pieces, sixteen three inch pieces, and four five inch pieces; one yard of thin wire that maintains its shape when bent (can be purchased at hardware and craft stores); scissors to cut wire
-tape

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Procedures:

NOTE TO TEACHERS: This activity asks students to build models of ionic and covalent bonds between atoms. Students must first have a basic knowledge of the atomic properties of different elements prior to your using this lesson. Additionally, the lesson asks for teachers to help students define the parts of an atom, a molecule, an ion, an ionic bond and a covalent bond. Your chemistry textbook should have good definitions and explanations for you to provide for your students when necessary in the lesson.

1. WARM-UP/DO-NOW: In their journals, students respond to the following review items (written on the board prior to class): Diagram an atom, labeling where one would find protons, neutrons and electrons. Write a definition for each of these parts of the atom by its label. Then, briefly define the term "molecule" and explain how molecules are formed. Students share their answers. As a class, agree upon definitions for these terms (which you should then write on the board for students to copy): atom, proton, neutron, electron, molecule. Be sure to include how many electrons can be held on each of the three shells (two electrons at the k-shell, eight electrons at the l-shell, and two electrons at the m-shell) as well as how to determine the number of electrons each element has based on the information provided on the periodic table of the elements. Then, ask students to discuss what scientists have learned from studying and experimenting with atoms and molecules.

2. As a class, read and discuss "Glue of Molecular Existence Is Finally Unveiled," focusing on the following questions:
a. Why and how do electrons bond to each other?
b. What do the new pictures of electronic bonds tell us about them that we did not already know?
c. Why would scientists want to learn "why it is that certain compounds of copper and oxygen can conduct electricity without resistance at relatively high temperatures"? How might this knowledge be applied?
d. How did scientists capture these new images?
e. What did scientists use to think atoms looked like, and how have those earlier perceptions changed?
f. What three types of bonds are described in the article, and how do they differ?
g. Why haven't orbitals been imaged before now?
h. Why was it so difficult to detect "the subtle changes in shape of bonds connecting copper and oxygen atoms," and why are these changes in shape important finds?
i. What different effects are caused by the scattering of x-rays than by the scattering of electronic beams? How did this scattering help scientists to understand the images they were seeing?
j. What is the difference between a cuprite and a cuprate, and how might this information be used in the future?
k. Why might scientists want to develop a "way for getting at where the electrons are in extended materials"?

3. Discuss the three main types of electronic bonding: metal-to-metal, ionic, and covalent. Define and illustrate each type of bond on the board for students to copy into their class notes. Be sure not to go on to the model activity below until students are sure that they understand specifically how ionic and covalent bonds work.

4.  Divide students into pairs.  Explain to them that they will work with a partner to perfrom two related projects.  The first project is the element research report.  Allow each group to choose a pair of elements that are able to bond together either ionically or covalently (teacher must approve the selected elements to ensure they will bond).  Each student in the pair will select one of the elements and research it.  Individually, they will create a word-processed advertisement of their element.  The report will include a picture of the atom and pictures showing the element in real-world applications.  The advertisement should include facts of the element and should "sell" itself to the partner student's element.  For example, an advertisement for Hydrogen should sell itself to Oxygen, scientifically (so they can share electrons and balance themselves) and commercially (so they can make water).  This should take 2-3 class periods to complete. 

5. Once both students have completed their reports, explain to them that they will now be demonstrating their understanding of ionic and covalent bonds by creating models of one of these types of bonds. Distribute to each pair a bag containing the gumdrops, bamboo skewer pieces, wire and scissors. Explain, using the sample bag of materials, the purpose of the different materials by creating a model of sodium chloride as an example. Each large gumdrop represents the nucleus of an atom. The small gumdrops represent electrons. Students should note that there are two colors of gumdrops, and each atom to be created should use one color; for example, if creating sodium chloride, the electrons in the sodium atom should be one color and the electrons in the chlorine atom should be the other color. The different lengths of bamboo skewers will help students create the different shells of electrons. The wire will connect to the gumdrops to create the circular outline of the shells.

6. Each pair will then use the materials in their bags to create models of the ionic or covalent bonds that their particular elements would form. Students should understand that depending on the bonds they are creating, they may not use all of the materials. Ask that when a pair finishes a model that they raise their hand to notify you that they are ready for you to check the model. Once you "approve" the correctness of a model, the pair tapes the slip of paper with the type of bond to one of the skewers in a way as to not obscure the ability to understand what atoms are bonding (so others canlook at them and try to figure out the bond). In a future class, the students will present their reports and models to the rest of the class, explaining the bonding relationship.

Further Questions for Discussion:
--Why are scientists interested in understanding atoms?
--What is chemistry, and why is this an important field of scientific study?
--What would you consider major achievements in the field of chemistry thus far?
--In what ways does chemistry often affect technological innovation?
--What information can be found on the periodic table of the elements, and how is this information organized for each element?
--In what careers is chemistry used, and how? 

Vocabulary:
assemblages, atoms, orbitals, lobes, arrays, theoretical, intractable, superconductors, lattice, nucleus, quantum, covalent, ionic, impinging, diffraction, composite, qualitatively, discernible