Cristina R. David

 

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Bond with a Classmate Lesson

I. NYS Standards:

 

Standard 4 – The Physical Setting

Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

Key Idea 3: Matter is made up of particles whose properties determine the observable characteristics of matter and its reactivity.

                                    Performance Indicators:

3.3: Develop mental models to explain common chemical reactions and changes in states of matter.

3.3f There are more than 100 elements. Elements combine in a multitude of ways to produce compounds that account for all living and nonliving substances. Few elements are found in their pure form.

3.3g The periodic table is one useful model for classifying elements. The periodic table can be used to predict properties of elements (metals, nonmetals, noble gases).

 

II. Objectives – The learner will be able to:

 

III. Purpose:

Most of the substances we see around us are composed of several different elements that have combined to form compounds.  There are very few elements that exist in nature in their pure form.  For example, water is made up of hydrogen and oxygen.   It is important for students to understand how elements can combine to form compounds and which elements are likely to combine.  The key to this is in the number of valence electrons that an element has.  We use the analogy of a collection.  Imagine that someone has a collection of state quarters and they only need one more.  You have the quarter that the other person needs.  It would be easy for you to give up your quarter because you don’t have a collection of quarters.  This is analogous to how sodium (Na) and chlorine (Cl) combine to make table salt.  Na has one electron that it can easily give to Cl, which really needs just one more electron. 

 

IV. Materials:

 

 

V. Anticipatory Set:

I will begin by asking students what it is called when elements combine – compounds.  Ask students if they think that the substances that are around us (the air, ourselves, the desk, etc.) are made of compounds or one single element.  Explain to students that most of the things around us are made of compounds – the combination of more than one element.  For example, water is made up of hydrogen and oxygen.  There are very few elements that exist in nature in their pure form.  Remind students that yesterday we learned how and why elements combine – to get satisfaction (this means having a full outer shell).   We looked at the example of sodium (Na) and chlorine (Cl) – they are a match made in heaven!!  Why?  Students should answer that Na would like to lose one electron to get satisfaction and Cl would like to gain one electron to get satisfaction.  Remind students of the analogy that we used – it’s like having a collection (see collection analogy in Purpose section). 

 

VI. Modeling:

I will begin by reviewing the material that was learned yesterday:

  1. When we draw electron dot diagrams, the dots represent the electrons in the outermost shell – these are called the valence electrons.  The valence electrons dictate what other elements a particular element can combine with. 

  2. Recall that there is a pattern with the valence electrons in the periodic table (Put up note sheet on overhead from yesterday).  All the elements in the 1st column have one valence electron.  The elements in the 2nd column have two valence electrons, and so on.

  3. Elements combine to get satisfaction.  Yesterday we learned about how Na and Cl are a good match.  Now, we will look at two more examples: hydrogen and chlorine to make hydrochloric acid (HCl) and aluminum and sulfur to make magnesium sulfide (MgS). 

  4. Recall that when an atom gives up electrons, it becomes positively charged.  When it gains electrons, it becomes negatively charged. 

  5. Finally, remember that the elements in the right hand column already have 8 valence electrons, so they don’t react with other elements. 

 

VII. Guided Practice:

  1. Students will now practice the concept of combining specific elements to make compounds. 

  2. Pass out one element card to each student.  Also, give a small handful of “electrons” to each student (about five). 

  3. Using a periodic table, have students place the correct number of electrons around the element symbol, creating an electron dot diagram.  The student may need to use the scrap paper to draw out the atom.  This will help them determine how many valence electrons the element has. 

  4. Once students have completed their electron dot diagrams, have them all stand and find a classmate with an element that they can pair with.  For example, a student with an Li card would try to find a student with a group 17 element card (F, Cl, Br, or I).  Instruct students to sit on a desk once they have found a partner.  If they have an element that doesn’t react, ask those students to sit against the back wall. 

  5. Once all students are sitting on desks, ask students to stand if they have the element that will be donating electrons.  Once all the correct students are standing, have them sit back on the desk.  Then, ask students to stand if they have the element that will be receiving electrons.  Once all correct students are standing, have them sit back on the desk. 

  6. Ask the donaters to donate their electrons to their partner.  Have the receiver (the partner) put those electrons on their element card.  Now, ask students to put their hand on their head if they have become a positively charged ion.  Ask students to put their hand on their head if they have become a negatively charged ion. 

 

VIII. Independent Practice

  1. Students will now exchange element cards with someone other than their current partner. 

  2. Have each student remove all electrons and then place the correct number of electrons around the element to make the proper electron dot diagram. 

  3. Remind students that they should be able to “draw” the electron dot diagrams fairly quickly at this point, and without the help of a teacher. 

  4. Repeat steps 5-7 above. 

 

IX. Assessment:

Attainment of the objectives for this activity will be assessed via the following:

 

Immediate: During the activity, we will be looking to see that the students are correctly able to determine the number of valence electrons for each element and can properly draw an electron dot diagram.  We will also be looking to see that students are able to “match” elements according to the number of valence electrons there are.  Finally, we are looking to see that students understand the difference between positive and negative ions

 

Mid-range: Students will be assessed on their basic knowledge of the atom and its valence electrons via their 3-D atom model, which is due tomorrow (April 4).  We will be looking for accuracy of the model and how well they followed the criteria given. 

 

Long-term: Students will be tested on this material on their weekly test that is given on Fridays. 

 

X. Closure:

To close the lesson, I will remind students that we have learned about different elements and what makes them different (the number of protons, neutrons and electrons).  Now, we see that these differences dictate how an element can combine with another element to make compounds.  When these elements combine, they make a completely new substance or sometimes they make two new substances!  Once again, these substances are called compounds.  Tomorrow, we will see a cool demonstration where two new substances are formed in a rather explosive way!  Also, you will learn what substances were formed and how. 

 

We also learned a little bit about trends in the periodic table.  After the break, we will end the chemistry unit by studying the periodic table more in depth to learn even more trends. 

 

 

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Last updated May 17, 2007