Ionic, Covalent, and Metallic Bonds

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Objective

Students will be able to differentiate between ionic, covalent, and metallic bonds by analyzing a reading and performing a lab.

Big Idea

Ionic, covalent, and metallic compounds have specific chemical and physical properties.

Introduction

In this lesson students learn the basics of Ionic, Covalent, and Metallic compounds through a reading and performing a lab.  The Electrifying Solutions lab comes from the Health and Science Pipeline initiative's (HASPI) Medical Chemistry Curriculum with some revisions.  All of HASPI's lessons can be found on their website.  I have found that theses lessons are a great resource to bring real-world applications to chemistry class.

  • This lesson aligns with NGSS Performance Expectation: HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
  • This lesson aligns with NGSS Science and Engineering Practice 3: Planning and Carrying out Investigations because students are performing a lab. 
  • This lesson also highlights NGSS Science and Engineering Practice 2: Developing and using models because students are analyzing three models of bonding.

Within this lesson there are several resources needed.

  1. For the reading it is nice to have some type of ball for students to pass around.
  2. For the lab each station needs a conductivity tester.  Additionally there are eight solutions that are placed one at each station.  These include: 1% calcium salt solution, distilled water, 1% ethanol solution, 1% glucose solution, 1% lipid solution, 1% potassium salt solution, 1% protein solution, and 1% sodium chloride solution

Engage

10 minutes

To engage students in the lesson and revisit the idea of bonding, I review the lab we did the previous day.  This is the link to the Ionic and Covalent Inquiry Lab.

I go through each station calling on different groups of students to go over the claim and evidence that we gathered at each station.  The groups are organized based on the groups of the periodic table.  The engage section from my Unit 1 First Day of Class Lesson explains how I group students.

For example I will call on the Halogens group and ask them what we learned about conductivity.  I will expect them to reply with, "We learned that ionic conducts electricity and covalent does not."  I usually have to probe for the evidence in which case I expect to hear, "The ionic solution made the light bulb light up and the covalent did not."

I then tell students that we will continue to learn about ionic and covalent along with metallic bonds by completing a reading and lab.

Explain

30 minutes

To help students gain a general understanding of the three major types of bonds: Ionic, Covalent, and Metallic, I have them perform a reading where they explore models of the three types of bonds.

The paper that I use is adapted from Living By Chemistry's lessons on Bonding.  Living By Chemistry is a great book that often leads students into understanding concepts using inquiry and real-world examples.  To learn more about this great resource visit their website.

I have students read using the technique of Popcorn Reading.  See the reflection attached on Popcorn reading.

I have students first read about the types of bonds, and then read through and answer questions about the bonds.

As students read I stop them to add in tidbits related to what we already learned in the lab, to point out the information that can be gathered from the model, and to have them highlight important information. 

Also as students read the questions on the back I give students time to answer the questions.  This allows me to give hints to students concerning the questions, as in these examples:

  •  "Covalent substances do not conduct electricity, what evidence in the covalent model demonstrates this?" I tell student to pay attention to what happens with the electrons in this model compared to the others.
  • "Use the ionic model to explain why ionic substances are often brittle." I first make sure to redefine brittle for students.  I then hold up the ionic model I have in my classroom and reiterate how each cation is surrounded by anions and each anion is surrounded by cations.  I have them think about how this correlates to the structure (crystal) and therefore makes the substances brittle.
  • "Why might the location of the electrons in the metallic model help to explain why copper metal is ductile and malleable?"  I review the definitions of ductile and malleable for students.

Because of copyright issues I am not attaching the actual LBC worksheet I use. 

If you want to perform a similar activity you can have students read about the types of models and then ask questions to compare them.  This BBC site has information about the types of bonds.

Elaborate

60 minutes

In this section students perform a lab to understand how electrolytes are involved in the human body.

  • To begin the lab I pass out the lab to students and have them read the introduction to themselves.
  • I then highlight the fact that we will be looking at some common solutions found in the human body and understand if they are considered electrolytes or non-electrolytes.
  • For this lab I have students work in their table groups without assigning specfic roles, but do tell them to make sure that they are taking turns testing the substances.
  • I also stress to students that they are only writing down a few of the important aspects of the solution on their papers. 
  • This video shows how I explain the lab to students.

 

Evaluate

For evaluation I have students perform a quick quiz concerning the properties of Ionic and Covalent compounds.   When students are done with the quiz I have them turn in.

  • This is the answer key I use to grade the quiz
  • This is an example of a student's graded quiz.  This student missed the question related to melting points.  This was a common missed problem along with the differences in electronegativity values question.  Both of these are further addressed later in the unit.

I then have students work on completing their lab.  Many students need to take the evening to complete the answers so they turn in the following day. 

This is a lab which I do not grade with a rubric.  Rather I give them points for having their data table complete and answering each of the questions.  

  • Here is an example of a graded lab.  
  • The lab is worth 19 points with the table worth 8 points (1 point for data from each station), the questions worth 2 points each, and the conclusion worth 3 points
  • This particular student missed one point on question 4, "Explain why electrolytes are essential to the human body," because she did not use the examples in the introduction that we had discussed.  Her source of error dealt with the conductivity tester which was very common for students.  The other source of error could have been contamination or not holding the electrodes up completely.