Atomic Theory Development
Authors of unit: Rebecca Anderson, Elaine Baker, Jacob Davis, Jesse
Durdel, Debra Monigold, Garilyn Wells
Partner Projects: UIUC Chemistry Library, ICLCS
Intended Audience:
Grade Level: First year high school chemistry students
Subject Areas: Atomic theory development
Unit Keywords: Atomic theory, Democritus, John Dalton, J.J. Thomson,
cathode ray tube, plum pudding model, gold foil experiment, GeigerMarsden experiment, Rutherford model, Robert Millikan, oil drop
experiment, electromagnetic radiation, electromagnetic spectrum, Niels
Bohr, line emission spectrum, Bohr model, quantum mechanical, waveparticle duality, photon, photoelectric effect, Werner Heisenberg,
uncertainty principle, orbital, electron cloud, electron, proton, neutron,
quark
Summary of the Module
Rationale
1. Student will outline the history of the development of the atomic
theory and analyze the experiments and observations made by key
scientists that lead to the present view of the atom.
2. Students will generate their own explanations about the development
of the atomic theory, and the teacher will guide students to confront their
existing misconceptions about the atom.
3. Teachers will have resources available such as applets, computational
tools and web sites that will aid in illustrating the main historical
concepts, scientists and experiments in the development of the atomic
theory.
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4. Teachers will provide an interactive classroom module incorporating
applets, computational tools and interactive websites which will allow
students to explore atomic structure and infer atomic properties based on
manipulation of such virtual tools.
5. This is a resource for any high school chemistry teacher or science
teacher to be able to use as a unit or to use sections as appropriate to
supplement the curriculum in their classroom.
Use(s) of the Unit
Students will be able to:
1. Compare and contrast different atomic models.
2. Synthesize a timeline of the various atomic models, including
historical concepts and the key people associated with the development of
the atomic theory.
3. Analyze the scientists’ experiments and infer the various properties of
the atom.
4. Investigate applications of current atomic theory to explain natural
phenomena and the use of scientific tools.
5. Utilize various applets and computational tools as related to the
development of the current atomic theory.
Illinois Learning Standards
Science Goals 11, 12 and 13
This module addresses a variety of standards. Complete notation of
standards is included in the final footnotes.
Software needed and other hardware/software needs
Required hardware: LCD projector for lecture, computer lab (with
internet connection) outfitted with enough computers for each student to
work independently
Required software: Microsoft Word, Microsoft Excel, Microsoft
PowerPoint, Windows Media Player, Java, Adobe Flash Media Player
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Content of the Unit
This module is composed of three main parts:
Part 1: Lecture/Applet Demonstrations
In this section, you will guide the student through an Atomic Theory
PowerPoint presentation, which shows the student the progression of the
atomic theory. It also includes links to various applets and visualizations
to enhance student understanding of the concepts.
Part 2: Student Activities/Lab Activity
First, the student will research the history of the atomic theory and
prepare a timeline, highlighting the various scientists who contributed to
our current understanding of the atom and its behavior.
Then, the student will be self-guided through several applets which will
illustrate the various key scientists’ contributions. Each applet has a
companion worksheet.
Part 3: Student Assessment and Feedback
Each student will complete a quiz which will serve to assess what he has
learned throughout the module. In addition, each student will be asked to
complete an online survey which will provide valuable feedback to the
instructor regarding the overall perception of the module and the
instruction effectiveness.
Background Information:
Atomic theories have been discussed for centuries. Each theorist has had
a different idea, some based on facts as they were known at the time and
some based on erroneous beliefs about how matter is constructed and
used.
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As early as 400 B.C., Greek philosophers such as Democritus were
discussing questions about what matter was, how it interacted and what it
became after a change. He was the first person who speculated that an
atom was the smallest particle. The Greek definition of the word atom was
“indivisible”. A generation later, Aristotle presented a different view of
matter, describing it as a continuous substance called originally “hyle”,
and later “phlogiston”. As with all things, popularity matters and since
Aristotle was a respected philosopher, his theory became the accepted
definition. However, neither man had any supporting experimental
evidence. Until the eighteen century, Aristotle’s theory was accepted.
Two thousand years of commonly held belief was difficult to overcome. It
took cold hard facts, painstaking experimentation, great leaps forward in
technology and the willingness to look beyond the obvious to develop a
new theory based on facts.
Prior to the late 1700’s, most of our beliefs about matter were based on
simple observations. Matter was composed of earth, fire, water and air.
Without the tools to conduct painstaking experiments, we had an
incomplete knowledge of what all things were made of. In the late 1700’s,
our ability to experiment and our knowledge of what the resulting data
determined took a great leap forward. The hunger to explain the
interactions of matter drove the giants of science to explore ever deeper
into the inner workings of matter and the atom. Even today, we are
unsure of exactly what the atom is composed of. This module attempts to
take you from the earliest theories of Democritus to the possibilities of the
String Theory.
Descriptions:
Atomic Structure PowerPoint
In this Atomic Structure PowerPoint1,2 presentation, you will find a variety
of slides, which include visuals and simulations, that cover the history
atomic theory, major scientists contributing to the understanding of the
atom and subatomic particles,3,4 key experiments5 performed leading to
breakthroughs4,6 in atomic theory, and analysis of the conclusions7 made
by the major atomic theorists. This PowerPoint seeks to give the
instructor a sequential and historical perspective of the development of
atomic theory. The PowerPoint begins by investigating Democritus, an
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early Greek philosopher, and transitions to John Dalton, who laid the
foundation for the modern understanding of the atom. The PowerPoint
then moves into the J.J. Thomson, the cathode ray tube, and the discovery
of the electron. After the discovery of the electron, Ernest Rutherford, the
gold foil experiment, and the discovery of the nucleus are addressed.
Robert Millikan and the oil drop experiment are not addressed in the
PowerPoint, but could easily be included if desired. Niels Bohr, the line
emission spectrum of hydrogen, energy levels, and common
misconceptions are next explored.
The PowerPoint concludes by
describing the quantum mechanical model of the atom with a highlight of
Werner Heisenberg and his uncertainty principle. Schrödinger and Max
Planck are not covered in the PowerPoint. Other topics that are included
in the PowerPoint are characterizing atoms by counting protons, neutrons,
and electrons, types of electrons, and describing the location of electrons
with electron configurations and quantum numbers. A computer with
Microsoft PowerPoint and Internet access along with a LCD projector are
needed to deliver this presentation. This presentation can be given in
totality before the students complete the enrichment activities or broken
into segments allowing the activities highlighting each experiment to be
completed before covering the next scientist, contribution, and
conclusions. The length of the PowerPoint can be adjusted to fit the time
restraints of each individual teacher.
Cathode Ray Tube Investigation
In this cathode ray tube applet,8 students will investigate J.J. Thomson’s
cathode ray tube experiment and his conclusion that all of matter contains
electrons.
Teachers will need a computer lab with Internet access through Internet
Explorer to complete this activity. If a computer lab is not available, this
activity could be done as a virtual classroom demonstration.9,10 Students
will need to adjust11 the separation, plate length, and screen size to create a
cathode ray tube more like the one that J.J. Thomson used.12,13 Students
will then change the deflection to both positive and negative voltages to
create an electrical field and use a magnet with north and south poles to
create a magnetic field. Students can manipulate the speed of the beam
and the length of the plates to determine what affects the path of a beam
of charged particles.4 This activity could be extended by asking students
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to explore3 how analog televisions function as opposed to today’s flat
screens at the following link to howstuffworks.
Rutherford Gold Foil Simulation
In the Rutherford gold foil simulation,14 students will probe how atomic
theories transitioned from the atom being viewed as a solid sphere to
mostly empty space.15 Ernest Rutherford’s gold foil experiment was
critical to this modification of atomic theory. Teachers will need a
computer lab with Internet access through Internet Explorer and a Flash 5
movie player. Students will fire12 alpha particles at a gold atom and
observe the path of the alpha particle. A detection screen will record 16 the
path of the alpha particle. After shooting multiple alpha particles at the
gold atom, students can derive9,17 the shape and charge of the nucleus
from the path recorded by the alpha particles. Students will also observe
how many particles travel unaffected when moved away from the
nucleus. Thus, from this simulation students should reach the same
conclusions10 that Rutherford did – the atom contains a dense, positively
charged center while most of the volume of the atom is empty space.3
Students will also be able to apply the scientific method to identify 18
variables that can be changed.
Millikan Oil Droplet Simulation
In the Millikan oil droplet applet, students will look into how the charge
of an electron was determined.3 Teachers will need a computer lab with
Internet access through Internet Explorer. Charged oil droplets will
cascade from the top of the screen.10 Students will manipulate12 the
voltage9 applied to the apparatus and analyze11 how the charge affects the
movement of the particles.
Bohr Model Simulation
Using the Bohr Model Simulation, students can visualize3, 4 Bohr’s
theories and the way wavelengths of light are absorbed and emitted when
electrons transition from ground state orbits to excited state orbits and
back to lower orbits in the hydrogen atom. In order to use this simulation,
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students need access to a computer with Internet Explorer. Students can
manipulate11, 12, 13 the electrons of the atom and watch as different
wavelengths of light are absorbed and emitted from the atom as the
electrons jump between the orbits. We have included a worksheet with
this simulation that has the students read a little about atomic line spectra
and Bohr’s theory of distinct orbits before doing any changing of the atom.
This part of the assignment can be skipped if the teacher has already
covered this information. The worksheet then has students change the
size of the orbits of the displayed model of the atom and visualize what
color of light would be emitted because of the energy differences. The
worksheet concludes by having the students adjust the orbits to try and
get specific wavelengths of color. To complete the entire worksheet
would take approximately 25-30 minutes. From this point students would
be able to perform a flames test lab and a gas discharge tube activity and
explain the atomic spectra they are observing.
It must be cautioned that this is an activity to investigate a different model
of the atom, not necessarily the correct model of the atom. The goal is to
make sure that students understand that while Bohr was able to explain
some phenomena he observed, he could not extend his explanation to all
atoms and was not able to predict a correct model6, 22. This activity was
included to emphasize that his ideas helped to shape our current model of
the atom.
Models of Hydrogen Simulation
The Models of Hydrogen Simulation gives students an opportunity to
review all the models of the atom that were discussed in class. On this site
there are many things which the student can manipulate11,12 which allows
the student to view the different variables that make the prediction of a
model of an atom difficult. It also allows the student to see the
limitations6 of earlier models and helps them to see the evolution of the
atomic theory. In order to use this simulation the student must have
access to a computer with Internet Explorer and JRE or later for
Windows/Linux systems or JRE for Macintosh systems. When the student
enters the site, the first thing that can be changed is the
Experiment/Prediction button. Under the experiment part, the student
observes what scientists have seen in the past, an unknown shape that
when light is passed through, produces an atomic spectrum. Students can
choose to view the spectrum that is produced when light passes through
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the unknown atom. If the button is changed to Prediction, then all the
predicted models of the atom appear to the left of the screen. The student
can choose one and view what happens when light passes through that
certain model. The student can choose between the Billiard Ball Model,
the Plum Pudding Model, the Classical Solar System Model, the Bohr
Model, the DeBroglie Model, and the Schrödinger Model. The student can
choose to send white or monochromatic light through the atom. There is
an option to show the electron energy level diagram for the models that
came later than the Plum Pudding. Students also have the option to make
the light travel faster or slower. On the Schrödinger Model, quantum
numbers are given in the lower right hand corner of the atom showing to
which orbitals the electrons are being excited. This is a good review site
and would also help solidify the concept of absorption/emission spectra
they view from the gas discharge tubes and the flames test labs. The
student should be allowed at least 30 minutes to really go through this site
and see the different models and manipulate12, 17 all the different variables.
Target Lab
In the target lab, students will study12,19 the concept of electron clouds,
probability, and orbitals. Teachers will need a copies of the lab procedure
for each student and a felt tip marker and target for each lab group. A
computer lab is needed to analyze24 the data with a computational tool
such as Microsoft Excel or another spreadsheet and graphing program.10
This lab aims to confront the misconception perpetuated by the Bohr
model that electrons are found on a fixed orbit circling the nucleus like
plants circling the sun in the solar system. Students should gain an
appreciation for the likelihood of finding electrons in a certain region.
Students will need 45-50 minutes to complete the lab activity. Analyzing
the data with Microsoft Excel and answering the laboratory questions
would require an additional 45-50 minutes.
Spectrum Virtual Lab
When completing this virtual lab 3, 12, 20, students have the opportunity to
view emissions spectra using a spectrometer. Previously, this lab may
have been completed by students using spectrometers, tubes filled with
various gases and diffraction grating. This process is frequently difficult
for first year chemistry students. This lab allows them to see a clearer
picture of the emission data for various gases, collect data about the
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emission lines, and calculate the frequency of the lines viewed. Using this
information, students are asked to calculate the energy of the emitted
photons. After completing the unit, a quiz is available asking the students
to use their data on the emission spectra of the various elements to
identify a spectrum of an unknown element. To complete the lab,
students will need a computer with the following: Explorer and Sun Java
1.4.2_16 or later for Windows/Linux systems or Apple Java 1.4.2_16 for
Macintosh systems, copy of the lab and a pen. The quiz requires the use
of Microsoft Power Point and a projector.
Atomic Theorist / Model Timeline
This project combines history of the major contributors of atomic
theory with the chronology of the different types of atomic models in a
timeline presentation.21 Students will research11 and gather data on the
scientists and great thinkers who have shaped our perception of the
atom in the form of their role in history and why 22 what they did was
important to the development of the modern view of the atom.
Students will search the internet and books for photos of the scientists
and atomic models to use on their timelines. Students will also
describe, compare and contrast3 the differences between the various
models of the atom. As an extension of this project, students could
also relate great scientists with breakthroughs that affect our everyday
lives.23
Assessment Strategies:
Any of the labs can be used as an assessment tool. Teachers can also
collect oral feedback from students through questioning as students are
completing the virtual applets, simulations, and laboratory experiments.
Quiz – Five short answer questions asking students to compare and
contrast different models of the atom along with scientists, their
experiments and conclusions. This quiz will take 25-30 minutes to
complete.
Test – A summative evaluation can be given at the conclusion of the unit.
This test includes multiple choice, short answer, and matching. An entire
period is needed to administer this evaluation.
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Classroom Implementation
The Atomic Theory PowerPoint was used in a lecture style in segments to
outline the key scientists, their experiments, observations, conclusions,
and contributions to our understanding of the atom. The PowerPoint was
broken into different segments to allow the students to explore virtually in
the computer lab or hands-on in the chemistry laboratory the concepts
taught. For example, after the lecture on Rutherford conclusion that the
atom contains a dense positive region surrounded by mostly empty space,
students went to the computer lab to complete the Rutherford’s Gold Foil
Simulation. Each class watched the applets or simulations that were
hyperlinked in the PowerPoint including the “Constituents” video.
Students remarked that the “Constituents” video was “cool” and
“awesome.” Students also spent back-to-back days in the computer lab
exploring the Cathode Ray Tube Investigation and the Rutherford Gold
Foil Simulation. In one class, students demonstrated a better picture of
the particles on a microscopic or atomic level than in previous years.
Students were able to explain observations in terms of interactions
between charged particles. This observation was based on the students’
performance on the quiz that was administered. Most students also
completed the Target Lab. This lab helped students understand that the
exact location of an electron cannot be known; rather the location can be
described as a probability. However, not all classes used Microsoft Excel
to analyze the data. Some items listed in the descriptions section, such as
the Millikan Oil Droplet Simulation, Spectrum Virtual Lab, and Timeline
were not implemented because of time constraints or lack of computer lab
access. Overall students responded well to the variety in instruction, the
use of technology, and the hands-on activities such as the Target Lab. The
unit was concluded with a unit test.
Recommendations for Future Work
Future modification plans for this module fall under three categories;
creating an alternate feedback system, including alternate activities for
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classrooms with limited computer access and expanding the module to
include more information about current atomic theories.
When our group began work on this module, we realized immediately
that Quantum Mechanics/Atomic Theory was a huge topic. As a result of
our discussions, we decided to focus the first on the history of Atomic
Theories and the development of the Quantum Mechanical Model. As a
result, we have not moved this module past briefest references to smaller
particles of matter such as quarks or bosons, nor have we included other
newer theories such as String Theory or M-theory. We hope to extend this
module by researching information on some of these newer, less proven
theories. One of our other goals with this project is to help students
understand that all theories change, some theories are disproved and
some are completely wrong. Therefore, knowledge, especially in science
is never absolute. As the second half of this project, we would like to
include a PowerPoint presentation on some of these theories, exercises to
help students understand the theories and hands-on activities to illustrate
some of the strengths and weakness of both newer and older theories.
One of the difficulties we have struggled with as a group and we feel
confident other teachers will also struggle with, is the limited access to
computer resources. We plan to include activities that can be completed
with access to only a few computers. Where ever possible, we have
included instructions to allow the teacher to use this resource in a
demonstration situation instead of student manipulated. One possible
solution to this problem would be to create other activities the students
could complete while waiting to use computers. Students could then be
working on several parallel projects with some using computers and some
doing other non-technology oriented activities. This would allow each
student to move through the projects at their own pace and order, but in
the end all students would have access to the same activities. A timeline
would need to be created to allow the teacher to give students due dates
and completion points for collecting projects and grading their work.
The final difficulty our group had encountered is feedback data collection.
We created an online survey for students to complete about the module.
When this survey was created, we set the collection format incorrectly and
new data overwrote old data, without giving us group feedback. In
addition to this problem, several of the members of this group found it
impossible to schedule a time for an entire class to use a lab to collect the
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data at the same time. Some possible solutions to this problem are
creating an alternate feedback form which could be printed off, filled out
by students and then collected or creating an online survey that gives us
better access to the data collection process, allowing us to assign students
numbers to determine who has and has not filled out the survey. We
would also be interested in a separate feedback system for teachers who
use this module. We would like to obtain information from them on the
success of this module in their classroom and suggestions for
improvement. It is important that this module be completely user friendly
to all levels of computer users. The only way to determine this is to have a
wider audience of instructors use this module and offer us feedback. We
may be able to link a feedback system to this module or to make a form
instructors can fill out and then email or mail back to us.
1
Allan. ScienceGeek.net. http://www.sciencegeek.net/Chemistry/Powerpoint/Unit1/Unit1_files/frame.htm
(Accessed: June 2007).
2
Cathode Ray Tube Video. http://www.its-about-time.com/htmls/ac/cathode-ray_large.wmv (Accessed:
June 2007).
Chasteen, Thomas. Sam Houston State University.
http://www.shsu.edu/~chm_tgc/sounds/pushmovies/l2ruther.gif (Accessed: June 2007).
Cristy, Jeff. Constituents. http://www.jeffreychristy.com/# (Accessed: June 2007).
Davidson, Michael. Molecular Expressions. http://micro.magnet.fsu.edu/electromag/java/rutherford/
(Accessed: June 2007).
Goldman, Martin. Bohr’s Atom. University of Colorado, Boulder.
http://www.colorado.edu/physics/2000/quantumzone/bohr.html (Accessed: June 2007).
Illkirch; Kiel; Strasbourg. Spectra of Gas Discharges: the Applet. http://astro.ustrasbg.fr/~koppen/discharge/discharge.html (Accessed: June 2007).
Karlsson, Magnus. Millikan’s Oil Drop Experiment.
http://physics.wku.edu/~womble/phys260/millikan.html (Accessed: June 2007).
MrCristea. Quantum Mechanics – Indirect Observation. YouTube.com.
http://www.youtube.com/watch?v=Y8IQbL_DnGk (Accessed: June 2007).
2110400. The Atom Song. YouTube.com. http://www.youtube.com/watch?v=vUzTQWn-wfE (Accessed:
June 2007).
3
12.C.4b- Analyze and explain the atomic and nuclear structure of matter.
4
12.C.5b- Analyze the properties of materials in relation to their physical and/or chemical structures.
5
13.A.5b- Explain criteria that scientists use to evaluate the validity of scientific claims and theories.
13.A.5c- Explain the strengths, weaknesses and uses of research methodologies including observational
studies, controlled laboratory experiments, computer modeling and statistical studies.
6
13.A.4c- Describe how scientific knowledge, explanations and technological designs may change with
new information over time.
7
13.B.5e- Assess how scientific and technological progress has affected other fields of study, careers and
job markets and aspects of everyday life.
8
McIntyre, Tim. Cathode Ray Tube. University of Queensland.
http://www.physics.uq.edu.au/people/mcintyre/applets/cathoderaytube/crt.html (Accessed: June 2007).
©2011 University of Illinois Board of Trustees • http://islcs.ncsa.illinois.edu/copyright
9
11.A.4f- Using available technology, report, display and defend to an audience conclusions drawn from
investigations.
10
11.B.4c- Develop working visualizations of the proposed solution designs.
11
11.A.4c- Collect, organize and analyze data accurately and precisely.
12
11.A.4b- Conduct controlled experiments or simulations to test hypotheses.
13
11.A.5c- Conduct systematic controlled experiments to test the selected hypotheses.
14
Rutherford Scattering Animation. http://www.waowen.screaming.net/revision/nuclear/rsanim.htm
(Accessed: June 2007).
15
11.A.4a- Formulate hypotheses referencing prior research and knowledge.
11.A.5a- Formulate hypotheses referencing prior research and knowledge.
16
11.A.4c- Collect, organize and analyze data accurately and precisely.
17
11.A.4d- Apply statistical methods to the data to reach and support conclusions.
18
11.A.5d- Apply statistical methods to make predictions and to test the accuracy of results.
19
11.A.4a- Formulate hypotheses referencing prior research and knowledge.
20
11.A.5d- Apply statistical methods to make predictions and to test the accuracy of results.
21
11.A.5e- Report, display and defend the results of investigations to audiences that may include
professionals and technical experts.
22
13.B.5b- Explain criteria that scientists use to evaluate the validity of scientific claims and theories.
13.B.5b- Analyze and describe the processes an effects of scientific and technological breakthroughs.
23
13.B.5e- Assess how scientific and technological progress has affected other fields of study, careers and
job markets and aspects of everyday life.
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