A Brief History of Atomic Structure A Jigsaw II

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					A Brief History of Atomic Structure: A Jigsaw II Activity

                    Stephanie Valerio

                       C&I 302-S
                  Fouad Abd-El-Khalick

                    February 26, 2004
                  A Brief History of Atomic Structure: A Jigsaw II Activity


Subject: Science
Grade Level: 10th or 12th Grade
Lesson Duration: 90 minutes


Objectives

The students will be able to:
       1. identify the location of protons, neutrons, and electrons in the atom, and indicate the
            charge of each particle.
       2. match various aspects of atomic structure to its contributor.
       3. point out the strengths and flaws associated with each model of atomic structure.

         These objectives are derived from the Illinois Learning Standards for Science set forth by
the Illinois State Board of Education. Specifically, Standard 12.C.4b states that by the end of
the twelfth grade, students should be able to "analyze and explain the atomic and nuclear
structure of matter." (http://www.isbe.state.il.us/ils/science/scg12.html)


Students' Background

         Students need not enter this exercise with an idea of the past or current models of the
atom. However, students should be familiar with the terms atom, electron, neutron, proton, and
alpha particle. In addition, students should be familiar with general concepts in physics. In
completing this Jigsaw II activity, students will be reading material that, at times, is difficult and
advanced. However, this will be a good opportunity for these upper level students to be
exposed to complex scientific literature, and will enable some of the students to actually read
excerpts from the original works of their particular scientist. If one desired to teach this lesson
to a first-year chemistry class, less technical readings should be selected. Finally, this activity
will require students to work independently, as they gather their information, and within a
cooperative group, as they share their information with others.

Activity

        Atomic theory can be both an interesting and boring topic to present in class. On the one
hand, exploring the structure of the atom challenges the mind to think on a very small scale, and
to visual subatomic particles that can never be seen by the naked eye. However, as much as this
lesson is related to chemistry and physics, it is also a lesson in history. Although the history of
the atom dates back to the ancient Greeks, we will only focus on four modern theories of atomic
structure: Dalton, Thomson, Rutherford, and Bohr. Time constraints will prevent us from
covering the theories prior to Dalton, and limitations in the students math and physics abilities
will prevent them from studying Schrodinger's Quantum Model.
        In order to make this activity interesting, we will approach the history of atomic structure
using the Jigsaw II method, where each student is placed in a small cooperative group (roughly
four students) and assigned to a particular model (Dalton, Thomson, Rutherford, and Bohr).
The students will read and answer questions about their scientist individually and then meet in
expert groups containing each student studying a particular model (i.e. all those studying
Rutherford will get together in a group and discuss their answers to each question). After
collaborating within their expert groups, students will rejoin their original cooperative groups
and share their findings with each group member. Although each group member will have all of
the readings available to him or her, it will not be necessary for each student to read all of the
material. After comparing notes, students will quiz each other in order to prepare for a short
quiz to be taken individually. This lesson should take approximately ninety minutes.


Materials

        I am assuming the class size is roughly twenty-five students. This lab will be performed
in five groups of four students each and one group of five students.

      25 copies of John Dalton (1766-1844): The Father of the Chemical Atomic Theory
      25 copies of The Thomson Model of the Atom
      25 copies of Rutherford's Experiment - Part II: The Paper of 1911
      25 copies of The Bohr Model
      25 copies of each question sheet (100 sheets total)

Preparations

        The only preparation for this activity (once the materials have been selected) is
photocopying everything. I would do this the day before the lesson just in case technical
difficulties with the copy machine are encountered.
        The students will be divided into groups of six, so I will have them count-off by six and
assign each group number to a particular location in the room. Once they are in their groups,
students can pick which model they want to read about. After completing the reading and
answering their set of questions, the students will meet in their expert groups, whose meeting
locations will also be assigned by me. Once they finish collaborating in their expert groups,
students will return to their original location in their base groups and finish the activity from
there.


Introduction (5 minutes)

Teacher = T
Student = S

T: Today we are going to do an activity within cooperative groups to help us learn a little bit
about the various models of atomic structure. I am sure that many of you have heard about
these models before, however, we will be exploring this topic more in-depth. Before we get into
this activity, can anyone explain what I mean by atomic structure?
S: Atomic structure is just the way protons, neutrons, and electrons are arranged inside an atom.
T: OK, so it seems that you are operating under the premise that atoms are in fact composed of
smaller units called protons, neutrons, and electrons. For our purposes in the year 2004, I would
say that your interpretation of atomic structure is fairly accurate on a basic level. Once you start
reading in your groups, you will see that this picture of the atom is only a fairly recent one. Can
I get three volunteers to come to the board and draw a picture of what you think the atom looks
like?
S: (Three students come to the board and draw pictures resembling the Bohr Model).
T: Thanks. It seems that there are some common themes in each of the three drawings. Can
anyone identify a theme?
S: Each drawing has a nucleus surrounded by electrons.
T: Good, what else? Are the electrons in random places?
S: No, it looks like they are orbiting the nucleus in certain paths.
T: OK, good. What is in the nucleus?
S: Smaller particles- they are the neutrons and the protons.
T: OK, these are all good observations. Interestingly enough, this type of atom drawn on the
board is just less than one-hundred years old. Today, we are going to read some resources that
will help us to understand past models regarding atomic structure and why these past models
were replaced or altered to give a newer, potentially more accurate model of the atom.


Body of the Lesson (70 minutes)

       Overview (10 minutes)

T: Like I said earlier, this will be a group activity, so I will need everyone to go around and
count-off by sixes (the teacher picks one student to start). Now, all of the people with the same
number get together in your groups (the teacher assigns locations for Groups 1-6). Once you are
in your groups, you will have four models to choose from: Dalton, Thomson, Rutherford, and
Bohr. Group 1, because you have five people, you will have two people reading about Dalton.
You will also pick one person each to be an elaborator, an encourager, a materials person, and a
quizzer. Group 1, choose two quizzers. It would be a good idea to write your information
down so that you do not forget. If you are an elaborator, your job is to make sure the speaker
clarifies and expands on the information he or she is presenting so that the group has a thorough
understanding of the topic being addressed. Those of you that are encouragers, your job is to do
just that- encourage. Make sure everyone in your group feels appreciated and that their work
and information is valued. If you are the materials person, it is your responsibility to obtain the
reading materials and question sheets from me. Also, make sure that everyone stays on task, as
we will only have one period to complete this activity. Finally, if you are the quizzer, your job
is to prepare your group for the quiz by testing their knowledge of the material. As you get into
your groups, I will be going around the room and checking to see if your are in fact doing your
job. OK, before I go on with the directions, take a minute to choose a model you want to read
about and a job you want to do.
S: (The students pick their models and jobs).
T: (The teacher now asks for a show of hands to see that every group has chosen an individual
to read about each model. He or she then checks to see that each group member has chosen a
distinct job). OK, good. Will the materials person in each group come and get copies of the
readings and question sheets for each model for each person. If you have four people in each
group, how many total reading packets do you need to get?
S: 16, because there are four people in a group and each person gets four packets.
T: Good, the same goes for the question sheets. Here they are.
S: (The materials persons get the appropriate handouts).

       Individual Reading (15 minutes)

T: Before we start, let me warn the people who have chosen Thomson that the excerpt on the
first page is difficult to understand- do not worry about it. The rest of the handout will explain
what he is discussing. Also, for those of you that have Rutherford, an alpha particle is just a
helium nucleus (He2+). That should come in handy as you read your handout. Now, take about
15 minutes to read your own article and to answer the questions associated with that model.
You do not have to read each of the four articles- I am giving you the readings just in case you
want them for your own knowledge or for studying. Again- only read your handout and only
answer the questions for your model.
T: (15 minutes later) has everyone finished reading?
S: (Students indicate that they are finished).

       Expert Groups (10 minutes)

T: Now I want everyone who read about Dalton's model to meet over here (the teacher assigns a
particular location in the room and does the same for the three other models). You are now in
your expert groups. Go over each question in order to expand on your thoughts, check your
responses, and reach a consensus as to the best answer for each question. Take about 10
minutes to do this. (At this time, the teacher is just walking around the room, listening in on the
discussions. The teacher is not recording points for participation yet).

       Base Groups (25 minutes)

T: (Ten minutes later) Now I want everyone to return to their base groups. Starting with the
Dalton model, go through each question so that everyone in the group learns about that particular
topic. The Thomson model should follow along with Rutherford, and then Bohr. I will be
coming around to check how well each group is encouraging and elaborating (remember your
jobs?!) Take 25 minutes to complete this task.
S: What about the quizzers?
T: I will give you more time to do that after you finish sharing your information.
S: (Students fill out each worksheet).
T: (25 minutes later) Now, I want each group to begin studying for the quiz. Quizzer, your job
is to make sure that everyone is one the same page. I will be going around to each group again.
Your quiz will be in 15 minutes.
S: (Students quiz each other).
       Assessment- The Quiz (10 minutes)

T: (15 minutes later) OK, I need you to take everything off your desks except for something to
write with. Each person will be taking the same quiz individually (the teacher passes out the
quizzes) You will have 10 minutes.
S: (Students complete the quiz individually and with no talking).
T: Pass your quizzes up to me. I will have them graded for you by tomorrow. However, I
would like to discuss some of the answers right now.

Closure (15 minutes)

T: Before we look at the quiz, here is a tally sheet of how each group did with respect to
elaborating, encouraging, and quizzing. What seems to be the strength and weakness of each
group (the teacher goes through all six groups)? Keep these ideas in mind the next time we
work in cooperative groups.
T: Now, let's take a look at some questions on the quiz. Briefly, what are the four basic
premises of Dalton's chemical atomic theory?
S1: Elements are made of atoms.
S2: Atoms of the same element have the same mass.
S3: Atoms of different elements have different masses.
S4: Atoms only combine in whole number ratios.
T: Good, thank you. Which of these is wrong and why?
S: The second one is wrong because atoms of the same elements can have different masses- they
can have isotopes.
T: OK, what subatomic particle is associated with different isotopes for a given element?
S: Neutrons.
T: So why didn't Dalton postulate the neutrons would have an affect on the mass of the nucleus?
S: He did not have the knowledge of neutrons.
T: Exactly- Dalton had no knowledge of any of the subatomic particles, at least he never
published any evidence to support their existence. What about Thomson's model...can someone
draw a picture on the board to illustrate the plum pudding model?
S: (Student volunteers) In this model, the electrons are sitting in a positively charged medium.
T: Right, did Thomson believe that this positive charge had structure?
S: No, he did not suggest the existence of protons.
T: Good, what about gold foil experiment? What do we know about the characteristics of the
nucleus according to Rutherford?
S: The nucleus is a concentration of charge in a single point.
T: And, how does the size of the nucleus compare to the size of the entire atom?
S: The nucleus is way smaller than the rest of the atom- that is why the alpha particles were
rarely deflected.
T: Finally, what is the most significant feature of the Bohr Model?
S: Energy levels are quantized- only certain amounts of energy can excite electrons in an atom.
T: Excellent job! I am very happy with how efficiently you all worked today, and I was very
impressed by your communication skills within your groups. Tomorrow, we are going to look
at a more current view of the atom- one that involves electron clouds instead of electrons. We
will also discuss some of the major underlying principles in quantum mechanics.
Assessment

        My formative assessments would measure the efficiency and effectiveness of each group
in encouraging, elaborating, and quizzing. I will show the class on overhead summarizing their
strengths and weaknesses of each group as a whole. This will allow both the students and
myself to identity areas that are strong and areas that need improvement. The summative
assessment is the quiz. I will grade the quiz so that I can assign partial credit as I see fit and to
maintain a standard as to how this quiz is graded with respect to all of their other quizzes.

Formative:
     Encouraging (1 point per comment)
     Elaborating (1 point per comment)
     Quizzing (1 point per comment)

Summative:
    The quiz (see attached).
                                        Appendix

1. Worksheets
     Dalton
     Thomson
     Rutherford
     Bohr

2. Readings (Also, see attached hard copies)
      Dalton- http://dbhs.wvusd.k12.ca.us/AtomicStructure/Dalton.html
      Thomson- http://dbhs.wvusd.k12.ca.us/AtomicStructure/Thomson-Model-Intro.html
      Rutherford- http://dbhs.wvusd.k12.ca.us/AtomicStructure/Rutherford-Model.html
      Bohr- http://csep10.phys.utk.edu/astr162/lect/light/bohr.html

3. Quiz

4. Tally Chart (elaborating, encouraging, quizzing)
                                    Dalton's Model
                                           (1805)


1. What are the four basic premises of Dalton's chemical atomic theory?




2. Which premise is incorrect? Why?




3. What was Dalton's view of the atom?




4. What important contribution did Dalton make in terms of atomic weights?




                                  Thomson's Model
                                           (1904)
1. What subatomic particles (if any) were discovered by Thomson? Where any subatomic
particles known prior to his work?




2. What two problems did Thomson face in studying the electron? Why were they problems?




3. Describe Thomson's idea of corpuscles. Draw a picture to help illustrate your answer.




4. What is another name for this model? Why?




                                 Rutherford's Model
                                            (1911)
1. Summarize the major findings of the gold foil experiment.




2. How did these findings lead to a new view of the atom?




3. How does the size of the nucleus compare to the size of the entire atom?




4. According to Rutherford, what was the nucleus? What subatomic particles (if any) were
discovered?




                                      Bohr's Model
                                            (1915)


1. What force maintains the orbit of the electron around the nucleus?
2. What is the most significant feature of the Bohr Model?




3. Qualitatively speaking, how does one determine the difference in energy levels in a Bohr
atom?




4. What is the difference between energy levels in the bound or discrete states and the energy
levels beyond the ionization potential?




                                         Quiz:
                                     Atomic Theory


1. a. What are the four basic premises of Dalton's chemical atomic theory?
    b. Which premise is incorrect? Why?




2. a. Describe Thomson's idea of corpuscles. Draw a picture to help illustrate your answer.




    b. What is another name for this model?




3. a. Summarize the major findings of the gold foil experiment.
       b. How does the size of the nucleus compare to the size of the entire atom?




4. a. What is the most significant feature of the Bohr Model?




       b. Qualitatively speaking, how does one determine the difference in energy levels in a
Bohr
           atom?




                                        Tally Sheet:
                                       Atomic Theory
   Group               Encouraging                 Elaborating                 Quizzing
  Number

                    Tallies        Total         Tallies         Total      Tallies       Total
1


2


3


4


5


6