Metallic and Covalent Bonds- Formation and Naming

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Objective

Student will be able to explain the characteristics of metallic and covalent bonds including how to name covalent compounds through taking notes, doing whiteboards, and performing practice questions.

Big Idea

Metallic bonds involve delocalized electrons among metals while covalent bonds involve nonmetals which share electrons in molecular orbitals.

Introduction

In this lesson students delve into covalent bonding through taking notes and practicing with whiteboards and individual practice.  Students have already learned the basics of covalent bonds through the introductory lessons of Bonding Inquiry and Ionic, Covalent, and Metallic Bonds.

  • 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 2: Developing and using models because students learn to model the formation of covalent and metallic compounds.

Within this lesson the only resource needed is whiteboards, dry-erase markers, and erasers for the covalent naming whiteboard practice.

Engage

15 minutes

In this section of the lesson I engage students in the topic in two ways.

1. I have students do an Ionic Compound Quick Review to help reinforce what we have already learned about ionic compounds.

  • I pass out the Ionic Compound Quick Review Paper.
  • I give students about 5 minutes to work on the paper.  I allow them to use their notes and to work with their table partner if need be.
  • I go over the answers with students using the answer key.
  • I remind students that all of this content dealt with IONIC compounds and that today we are going to discuss METALLIC and COVALENT compounds which are different.

2. I have students perform Periodic Table Aerobics.   See my reflection on Kinesthetic Learners in Chemistry in the previous lesson on Ionic Compounds.

  • I have them perform aerobics to ensure that they recall the components (metals, nonmetals, or both) for Ionic, Covalent, and Metallic bonds.

Explain

60 minutes

In this section of the lesson I discuss metallic bonding (slide 2), covalent bonding (slides 3-5), how electronegativity differences dictate bond type (slides 6-12), and how to name covalent bonds (slides 13-17).

  • As students take notes there is an opportunity for students to perform practice questions.
  • They perform practice questions on slide 12 where they decide if each pair of elements would form an ionic, non-polar covalent, or polar covalent bond.  This is tricky and I have them try to solve the problems through both using the electronegativity values and by looking at the location of the elements on the periodic table (I just remind them that Hydrogen has the same electronegativity value as Phosphorous). 
  • They also perform practice questions on slides 16 and 17 for covalent naming.  Students find covalent name MUCH easier than ionic, the only issue is remembering the proper prefixes.
  • This is a copy of one student's filled in notes.

Elaborate

35 minutes

For this section of the lesson students have an opportunity to practice covalent naming.  To help them I have them keep their notes out with the table of prefixes.  Also, I have a poster in the classroom of the prefixes for covalent compounds for students to refer to.

The first thing students do to practice naming covalent compounds is doing Partner Whiteboards.

  • I have students work in pairs and each pair needs one whiteboard, one dry erase marker, and one dry eraser.  I have students work with partners to encourage them to discuss why they think that a certain answer is correct.  I periodically remind them to switch partners in terms of who is doing the writing throughout the whiteboard session. 
  • This is the PowerPoint I use.

1. I put up a problem on the PowerPoint and then have students hold up their answers. 

2. I either give thumbs up or down and if they get it incorrect they should retry. 

3. After most students answer I go onto the next answer.  If it is one that many get wrong I go over why the correct answer is correct either by myself explaining or having a student explain how they determined the answer. 

4. See my embedded Covalent Whiteboard Reflection to get a better idea of how this works in my class.

  • Most students do well on the whiteboards.  The most common mistake is students using the wrong prefix, not properly changing the ending of the second element, or not putting the # of atoms in the correct location.  These are pictures (1, 2, 3) of some of the common mistakes.
  • If you do not have access to whiteboards you can have your school order some such as these at Office Max or you can also have students write answers on a sheet protector with a piece of paper in the middle.

The second thing that students do is individual practice with covalent naming. 

  • They do this by completing a Covalent Naming Practice Paper
  • As students complete these questions I have them check their answers with the class answer key and then have them start their homework.

Evaluate

For homework students perform the practice questions at the bottom of the last page of their Unit 3 Lecture 2 Notes Graphic Organizer.  

I stamp the homework for completion when students come to class the next day. 

I then go over the answers to the homework using the answer key.

Most students that have problems with the homework get confused with naming (remembering which rules are for Ionic and which rules are for Covalent).  Also many forget to write down whether the covalent compounds are polar or non-polar.   This student work shows a copy of the filled in homework by a student on the third page.