Discovering Periodicity: Hands-On, Minds-On Organization of the

Article pubs.acs.org/jchemeduc

Discovering Periodicity: Hands-On, Minds-On Organization of the Periodic Table by Visualizing the Unseen Jodye Selco,*,† Mary Bruno,‡ and Sue Chan§ †

Center for Excellence in Mathematics and Science Teaching, California State Polytechnic University, Pomona, Pomona, California 91768, United States ‡ Kordyak Elementary School, Rialto Unified School District, Rialto, California 92376, United States § Kolb Middle School, Rialto Unified School District, Rialto, California 92376 United States S Supporting Information *

ABSTRACT: Understanding how the periodic table of elements is organized and how to read information from it is fundamental for understanding chemistry. Introductory chemistry courses usually include discussions detailing what elemental information can be determined by virtue of its position on the periodic table. Although many people have been exposed to these ideas, they still do not understand how the periodic table is organized. This article describes new discovery-based lessons that enable students to explore the organization of the periodic table and learn how to read the information embedded within it. This method guides students through hands-on, minds-on activities that allow them to develop visual−spatial images of the role valence electrons play in the formation of molecules from atoms and in the organization of the periodic table. This new constructivist teaching method has been successfully used with learners of many ages from eight years old through adult learners. KEYWORDS: Elementary/Middle School Science, High School/Introductory Chemistry, Curriculum, Public Understanding/Outreach, Collaborative/Cooperative Learning, Hands-On Learning/Manipulatives, Inquiry-Based/Discovery Learning, Periodicity/Periodic Table, Standards National/State, Student-Centered Learning

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those states that has its own set of standards.8 One of the California fifth-grade standards states the following:8 Students know that each element is made of one kind of atom, and that the elements are organized in the periodic table by their chemical properties. This means that California expects 10-year-old students to understand how the periodic table is organized and to be able to apply this understanding to make predictions about a variety of chemical properties. There are many problems with this expectation. First, elementary school teacher preparation programs in California9 (and many other states) require as little as 10 weeks (1 quarter) of college-level physical science prior to certification. Second, if teenagers and adults do not learn much from traditional lessons about the periodic table and the information it contains, how can we expect 10-year-old students to come away understanding how the periodic table is organized? As part of a professional development program for teachers,10 we set out to devise a way for both teachers and students to understand the information contained within the periodic table. Challenging though this may be, our goal was to develop a hands-on inquiry method that allowed the participants to construct their own

nderstanding how the periodic table of elements is organized and how to read information from it is fundamental for understanding chemistry. Introductory chemistry courses usually include discussions detailing what elemental information can be determined by virtue of its position on the periodic table. Many people who have been exposed to these ideas still do not understand how the periodic table is organized. There have been numerous articles about the periodic table that include where the s-, p-, d-, and f-blocks should be placed,1 how to make “living” periodic tables,2 patterns in the periodic table,3 “unexpected” ways of representing the periodic table,4 and historical stories about the periodic table and its development,5 as well as jokes, puzzles, mnemonics, and games about elements and the periodic table.6 However fun and interesting these ideas may be for chemists, they do not facilitate the learning of how the periodic table is organized. National7 and state science standards are demanding that (among other things) students as young as those in the fifth grade understand the basis for a variety of chemical processes, including prediction of molecular formulas, knowing how to tell the difference between chemical and physical changes, knowing how physical and chemical properties can be used to separate substances, and knowing how to predict chemical and physical properties of elements and compounds. Not all states use the national science standards as their own; California is one of © XXXX American Chemical Society and Division of Chemical Education, Inc.

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dx.doi.org/10.1021/ed300623b | J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

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no meaning. Students are told that the coloring of the atoms and valence electrons helps organize the lesson but has no real meaning.

understanding from activities that were scientifically correct, yet intellectually accessible to all learners.

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Building Binary Main-Group Compounds

DEVELOPING INQUIRY MATERIALS TO TEACH VALENCY AND PERIODICITY Atomic structure was unknown to Mendeleev;5a he decided where to place elements on the periodic table according to “chemical properties” of the elements and their “elemental weight”. According to Mendeleev, “chemical properties” meant the combining ratios of the elements in binary compounds, such as chloride salts.5a Modern chemists now know that the elements are organized on the periodic table by number of protons within the nucleus and the number of valence electrons. These are quite sophisticated and abstract ideas. As chemists, we cannot see atoms, let alone valence electrons in action. In order to get these ideas across to learners of all ages, we realized that we needed to address two major concepts. First, learners needed some way to determine what the combining ratios were in simple binary main-group compounds. Second, learners needed to understand that it was the number of valence electrons that determined an element’s position on the periodic table, with elements having the same number of valence electrons being placed within a column. What many learners need to acquire an understanding of abstract ideas are concrete models to manipulate so that they can get appropriate images in their “mind’s eye”.11 Activating learners’ visual−spatial thinking in this way helps explain the relationship of the elements’ positions on the periodic table and enables transfer of ideas into more abstract frameworks at a later time.11 This means that we needed atomic models that contained all of the valence electrons explicitly displayed around which we could design lessons that were comprehensible to learners as young as 9 or 10 years old. Although many types of atomic models are available commercially,12 none of these shows all of the valence electrons. So we designed atomic models using table tennis balls to represent the atoms and (externally attached) pipe cleaners to represent the valence electrons. Table tennis balls were intentionally chosen to provide spherical models as atoms; use of flat pictures induces incorrect “mind’s-eye” images that tend to induce misconceptions (e.g., that atoms are two-dimensional). We color-coded the main-group atoms by number of valence electrons to facilitate formative assessment (visual spot checking) by the teacher during the lesson; the paired and lone electrons have different colors for the same reason. Directions for construction of these atomic models are available in the Supporting Information. It is stressed to students that although colored table tennis balls and differently colored pipe cleaners are used, these are only “teacher tricks” and that the colors have no meaning in these models.

To construct binary main-group compounds, student groups are asked to choose two different types of atoms from the group set. Students are told they are going to pair up lone electrons between their two atoms until all lone electrons have a partner (lone pair electrons already have a partnereven though it is an “internal” partnertherefore they are not involved in making chemical bonds), and that they can only use the two types of atoms chosen by their group. Student groups then make binary compounds using the two types of atoms chosen by their group, even if it requires “borrowing” atoms from other groups. Students are “done” when all of the lone electrons have a bonding partner. The rules for formation of stable molecules are presented in Box 1, and those for making binary compounds are presented in Box 2. Box 1. Rules for Making Molecules • To form stable molecules, electrons must ultimately be paired. However, they only pair internally when forced to do so. • Unpaired electrons (lone electrons) are “reactive”. In order to become more stable, they need to find external electron partners because they do not have internal partners. Atoms no longer do chemistry when all electrons are paired. • Making new electron−electron connections between atoms is what we call chemistry or a chemical reaction. Atoms and molecules do this to become more stable. Box 2. Rules for Making Binary Compounds • Use only two differently colored (or two types of) atoms to connect the unpaired electrons: use as many of each as needed, borrowing from other groups as necessary. • Compounds are complete when all unpaired electrons have a single partner and none are left unpaired. Students are then instructed to “do chemistry” and make a binary compound out of the two chosen types of atoms. While making molecules with their atomic models, students often ask if multiple bonds between atoms are allowed. Of course, the response is yes. The atomic models were designed with the valence electrons in VSEPR14 geometries, so any electron−electron connections that they can physically make can appear in nature. To answer the question as to whether or not a quadruple bond is possible, once a student connects three of the electrons between two four-valence electron atoms, it is clear that the fourth electron on each of the two atoms is pointing in the opposite directions, which is exactly what a model should show. Students also “see” why some compounds such as ClO or HO are not “stable” because there is an unpaired electron “left over” after making this molecule with the models. Of course, these models cannot correctly model all of the known molecular combinations involving main-group atoms (e.g., SnCl2 or O2); then again, none of the other available models can be used to correctly model these compounds.

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USING THE ATOMIC MODELS After a discussion13 about what atoms are made of and how the subatomic particles are organized within atoms, students are presented with a bag of atomic models that contains at least one of each type of main-group element. These models are discussed with students so that they know that the table tennis ball models show only the valence electrons of the atom while the nucleus and core electrons are unseen in the interior, the valence electrons are color coded as to whether they are lone or paired electrons, all electrons are the same regardless of their “color”, and the colors of the table tennis ball atom models have

Writing Chemical Formulas

Atoms with different numbers of valence electrons are colored differently;15 when students are asked what combinations they B



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each type of main-group atom. Students are then asked to examine their “data” (atomic models), organize them, and then figure out where their “data” belongs on the data table.17 Students are then instructed to place their data on the data table. (This is done using hook-and-loop dots on both the atoms and the periodic table.) It is stressed that the colors of the atoms and electrons are not real. The fact that they are colored at all is just a “teacher trick” for organizing the lesson. Surprisingly, even quite young students are aware of these “teacher tricks” and tend not to pay attention to the colors, for the most part, during the rest of the activities. We were surprised to see students counting and recounting the number of valence electrons on each atom without noticing that the atoms of a given color all had the same number of valence electrons. A picture of the main-group atoms placed onto the maingroup portion of the periodic table is shown in Figure 2.

were able to make, a possible answer might be three pinks and two purples. Answers are recorded for everyone to see; these combinations are then manipulated into the equivalent of molecular formulas by first abbreviating the “color name” so that the compound becomes 3 P and 2 Pu, and further abbreviation yields P3Pu2. In this way, the meaning of the subscripts is made explicit; the discussion that follows makes clear that P3Pu2 is quite different from P2Pu, which they can actually now “see”. We also make clear that when P3Pu2 is a saturated compound, 2 P3Pu2 is not the same as P6Pu4, because the latter cannot be constructed. This development of chemical formulas addresses one of the problems common to chemistry novices:16 they do not really understand that the subscripts within a formula dictate a specific compound, and that changing the subscript numbers (e.g., while balancing a chemical equation) changes the compound itself. By choosing appropriate colors for the atoms, you also can demonstrate that some element symbols have a second (lower case) letter so that the elements beginning with the same letter of the alphabet are distinguishable. This concept too is often quite confusing to chemistry novices.

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PERIODICITY

Main-Group Elements on the Periodic Table

A conceptual difficulty learners of chemistry have is that the main-group elements are not all together on the periodic table. To be able to place the alkali and alkali earth metals next to the p-block atoms, we constructed a large periodic table with four separate blocks so that the transition metals and actinides and lanthanides could be removed from our periodic table; in this manner, only the main group elements would remain on our periodic table. Removing the transition metals and lanthanide and actinide blocks from the periodic table in front of the students reinforces the concept that these elements may have similarities to, but are different from, the main group elements. Figure 1 shows the portion of the periodic table that contains only the main-group elements. Figure 2. Atomic models of the main group elements added to the s- and p-blocks of the periodic table.

In looking at Figure 2, it should now become clear how the color-coding of the table tennis balls and pipe cleaners can be used to see at a glance how students are progressing in the assigned task of organizing their “data” onto the “data table”. Connecting the Making of Molecules and the Organization of the Periodic Table

Once the atomic models are correctly placed onto the periodic table, discussions about the periodic patterns observed occur. One of the points stressed is that because valence electrons are responsible for chemical behavior, the elements within a family or column on a periodic table must have similar chemical behavior (combining ratios) because every atom within a column of the periodic table has the same number of valence electrons. This reinforces Mendeleev’s original idea about chemical behavior and the organization of the periodic table5a upon which the California standard is built. It is now clear, because it is visible, why the elements in columns 1 and 7, 2 and 6, and 3 and 5 all require the same number of bonds. This idea is quite problematic for nonchemists.18 A common question from students is, “How can two elements, one with only two valence electrons and another with six valence electrons, only make two molecular bonds?”

Figure 1. Main group elements of periodic table with the d- and f-blocks removed.

It is helpful to point out that the periodic table (even a subset of it) is just a data table: a place for organizing data. Students examine a bag containing atomic models that contain one of C



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Figure 3. Main group and transition metal atomic models placed onto the appropriate portions of the periodic table to demonstrate periodicity.

The answer becomes quite clear because students can “see” why this is the case if only the lone valence electrons are capable of forming bonds. The Rest of the Periodic Table Is Organized Too

Although the main-group elements are usually the focus of introductory courses, there is much more organization to the periodic table than elements with a maximum of eight valence electrons. This new atomic model set also contains transition metal atomic models. These are constructed in a similar manner to the main-group elements, but these “atoms” contain between 3 and 12 valence electrons placed around the ball using VSEPR geometries. While some may argue that this representation is not technically correct, none of the moleculemaking activities are done using these models. Instead, they are used solely for the sorting of the new data (elements) onto the new portion of the periodic table (the d-block) that has been added back into the periodic table. Additionally, these atoms are all painted the same color (we used white) so that students can only rely upon the number of valence electrons (and not a color) for clues about where the data should reside on the data table. A picture of atoms on the first three blocks of the periodic table is shown in Figure 3. In looking at Figure 3, it now becomes apparent why the use of two colors of chenille stems allows for seeing at a glance how students are progressing in the assigned task of organizing their data onto the data table. When the transition metal atomic model atoms are introduced, the learners are again reminded that the color of the “atoms” and “electrons” is not real and that its only purpose is as a “teacher trick”.

Figure 4. A water molecule made from the table tennis ball models.

because the lone pairs of electrons are now explicitly showing, as can be seen in Figure 4. Even though these models do not demonstrate polarity of individual bonds, Figure 4 still makes visible the fact that the electron density is greater around the yellow oxygen atom than on the red hydrogen atoms. Using atomic models such as those described here enables learners to visualize what happens at the atomic level. Teaching with visualization models such as these might help demystify chemistry, as well as reduce the amount of chemical misconceptions.18

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TEACHING WITH THESE ATOMIC MODELS A group of fifth grade teachers from an urban school district participated in a grant-sponsored project in 2004−2005 that had a 40 h professional development workshop that included the lessons detailed here. All 40 h focused upon chemistry in 2004−2005; approximately 20 h involved using these atomic models during instruction. No other professional development in science was available within the district during this time. The majority of elementary schools had one “lead teacher” who participated in a lesson study in which groups of teachers designed, taught, and revised lessons based on student outcomes and responses. As part of the overall project, this lesson became the cornerstone of teaching the unit on physical science at fifth grade. At the same time, the mandatory district-wide assessment of science at fifth grade began to include questions about this lesson and its activities. In each of the subsequent three years of this science professional development project, a 40 h workshop was presented that focused upon a different topic. The second year focused on Earth science; the third focused on life science; and in the last

Visualization of Atoms, Molecules, and Ions

These atomic models can help learners understand how to balance reactions by breaking the bonds (electron−electron connections) in the reactant molecules to form atoms and forming new bonds (electron−electron connections) between the product partner atoms. The models can be used to demonstrate how ionic and covalent bonds are different because the chenille stem “electrons” can be removed from one atom and attached to another “atom” to demonstrate the formation of ions that are electrostatically attracted to each other. However, these models do not predict when bonds will be ionic, polar, or covalent. The polarity of molecules also can be easily visualized D



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year, the focus was on science process skills (California standards calls them “Investigation and Experimentation”). As a part of the multiyear project, the lesson study activities and revision of district-wide science assessments continued with a focus on the science topic for that year. Although all fifth grade teachers in the district were invited to participate in the professional development workshops, 54% participated during the first year. The first year of workshops focused on the physical science standards; in California, the physical science standards at the fifth grade all address topics in basic chemistry.8 Throughout the four years of this science program, 49% of the 241 fifth grade teachers participated. Because end-of-year testing of fifth grade students on the California Standards Test (CST)19 includes science questions and is mandated by the federal No Child Left Behind Act,20 this provided an opportunity to examine and compare student performance.

Figure 6. Averaged classroom averages on the physical science (PS; chemistry) portion of the California Standards Test (CST; 11 questions total) for fifth grade students whose teachers participated in the chemistry professional development workshops (with PS PD) versus those students whose teachers did not participate (without PS PD) in the chemistry professional development workshops.

Evidence of District-Wide Fifth Grade Student Learning

Figure 5 shows fifth grade student performance throughout the school district on the science portion of the California

in different years) were statistically significant from scores of nonparticipants in 2005−2011 (data not shown). For 2004 (baseline) there was no statistically significant difference between the student performances in science for any of these groups of teachers. For reference, chemistry was the first topic presented in the professional development workshops that began in 2005. The data presented in Figure 6 demonstrate that students of the teachers who participated in the chemistry professional development workshops scored higher on the fifth grade physical science (chemistry) portion of the CST than did the students of teachers who did not participate, even if those teachers participated in other science professional development workshops in subsequent years. However, the physical (life and Earth) science performance of the students of all teachers has been increasing over the years of this study. Figure 5. District-wide student performance on the science portion of the California Standards Test (CST) over time.

Learning in Individual Fifth Grade Classrooms

Individual teacher classroom profiles can also be examined. Figure 7 shows data from the students in three different classrooms. Teacher 53 had mostly English learners who were found to be in the bottom two quintiles of the California English Language Level Development Test (CELDT)21 in their ability to read, write, speak, and understand spoken English. The data in Figure 7 indicate that the lessons described here are effective in teaching science to language learners. The Figure 7 data for Teacher 67 show student performance on the science portion of the CST for a special education classroom. The teacher had a high level of implementation of hands-on teaching of science and many years of experience in teaching students with special needs. Teacher 67 retired from teaching in 2007 after participating in professional development in both chemistry and Earth science. The data in Figure 7 indicate that the lessons described here and in the other science professional development sessions are effective in helping students with special needs learn science. Many of the teachers who participated in the professional development workshops inverted their classroom proficiency profiles on the science portion of the CST. The data for Teacher 24 in Figure 7 illustrate the classroom profile of a teacher who participated in the science professional development program for four consecutive years. This teacher had two students in the proficient and advanced range in 2005; by 2009,

Standards Test (CST). As the data show, the percentage of students whose scores are rated as proficient and advanced has been increasing at the expense of the students whose scores are mostly in the Far Below Basic and Below Basic ranges. From 2005 to 2011, 4.4 times more students are scoring at the proficient and advanced levels than had been previously. The CST science scores can be disaggregated to examine whether teacher participation in the professional development sessions where these lessons were presented correlated with the learning of chemistry (physical science) by their students. As shown in Figure 6, the students of teachers who participated in the chemistry professional development (labeled “With PS PD”) answered about 10% more of the 11 questions correctly than did the students of teachers who did not participate in the chemistry professional development sessions (labeled “Without PS PD”); t-test results indicate that the physical science (chemistry) score differences are statistically significant from 2005 through 2011 between these two populations. By comparison, t-test results of the overall scaled CST science scores (all three areas of science combined: life, Earth, and physical science) indicate that the differences in average classroom scores for teachers that participated in any of the science professional development sessions (different science areas E



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Figure 7. CST classroom proficiency profiles of teachers 53, 67, and 24 who participated in the professional development in chemistry (2005) and Earth science (2006). Teachers 53 and 24 also participated in the professional development in life science (2007) and science skills (2008). Teacher 53 had English learners whose English language abilities were in the CELDT (California English Language Level Development Test) bottom two quintiles. Teacher 67 worked with special needs students and had many years of teaching experience with special needs students; Teacher 67 retired in Spring 2007. Teacher 24 participated in all four years of the professional development program in science.

all but one student in the class scored in the proficient and advanced range of the science portion of the CST. Although the individual teacher data chosen shows some of the most impressive cases, the teachers who participated in the science professional development workshops had higher classroom averages in science on the CST; these differences were statistically significant when compared to the classroom averages of the teachers who did not participate in the science workshops. It also was clear that, during the workshops and lesson study sessions, the use of the atomic models made visible for teachers the organization of the periodic table as well as other atomic and molecular processes. This enabled these teachers to develop a tangible understanding of chemistry that they could then teach to their students.

Box 3. District Benchmark Questions 19. Copper is an element. What is the smallest unit of copper that still maintains the characteristics of copper? A. The atom B. The electron C. The nucleus D. The proton 22. Using your periodic table, determine which two elements have the most similar chemical properties. A. Fluorine and neon B. Neon and chlorine C. Argon and chlorine D. Chlorine and fluorine 23. The periodic table of the elements is systematically organized according to the A. Number of neutrons in an atom. B. Hardness of the elements. C. Chemical properties of the elements. D. Color of the elements on the periodic table. 35. Magnesium (Mg) and sulfur (S) chemically combine to form magnesium sulfide. Use the periodic table to predict the combining ratio of how many Mg and S atoms will combine to form magnesium sulfide. A. MgS B. Mg2S8 C. MgS2 D. MgS3

Assessing Fifth Grade Student Learning

New district benchmark exams addressing the state standards were developed and administered for the first time in 2009−2010. The California fifth grade standard regarding the periodic table states the following:8 1d: Students know that each element is made of one kind of atom and that the elements are organized in the periodic table by their chemical properties. The exam contained four questions that examined student understanding about individual elements and how the periodic table is organized. These questions are presented in Box 3. As can be seen from Table 1, over 51% of fifth grade students in the district understood what an atom is and answered question 19 correctly. More than 40% of the students understood that the elements in a family have similar chemical properties, understood that the overall organization of the periodic table is based upon the chemical properties of the elements (not the color of the atoms in the models), and could correctly predict the combining ratio of magnesium and sulfur. For each of these questions, a higher percentage of the students of teachers who had participated in the professional development covering the chemistry content answered correctly when compared with the rest of the students in the district. The year this exam was first administered (2010) only 17 of the 57 teachers (30%) at fifth grade who had participated in the chemistry professional development sessions in 2005 were still teaching fifth grade.

students learn about chemistry is in the eighth grade, which has a focus on physical science.8 Although some of the content addresses physics, more than half of the year focuses on chemistry. Examination data for eighth grade students over time are presented in Figure 8. The first cohort of fifth grade students affected by the chemistry professional development program was in 2004−2005; these students reached the eighth grade in 2007−2008. The percentage of students scoring in the proficient and advanced ranges on the science portion of the CST jumps from 25.8% in 2006−2007 to 38.4% in 2007−2008 as this student cohort reaches the eighth grade. Anecdotally, eighth grade district teachers in 2007−2008 noticed and remarked that the students that year knew more chemistry than students from previous years and wondered what changes had

Evidence of Longitudinal Learning

The students’ learning of chemistry persists beyond the elementary school level. The next grade at which California F



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and to visualize what happens at the atomic level during a variety of chemical processes. This new constructivist teaching method has been successfully used with learners as young as eight years old as well as with adults as part of a professional development program for teachers. Testing of fifth grade students indicates that use of the atomic models described here to help students visualize the normally unseen world of chemistry results in real understanding. This understanding is demonstrated by student performance on both district and state examinations. The examinations provide evidence that these methods for teaching elementary school students are effective for all students, including English learners and those with special needs. Students appear to build understanding of chemistry in fifth grade that is retained for years, as evidenced by the middle school physical science examination in the eighth grade and the high school chemistry exams administered by the state of California. Young students are not the only ones who seem to learn about the organization of the periodic table via this concrete method. When these lessons are shared with adult learners even those with Ph.D.s in a sciencethey report learning science from the lessons described here. Many of these adults were able to make new connections between what they were “seeing” and what they had learned in the past. This is likely not wholly because these people are visual learners, but because they required more concrete methods of learning than were presented in their chemistry courses.

Table 1. District-Wide Student Responses to Fifth Grade Benchmark Exam Questions in 2010 Distribution of Student Responses

Correct Answers,b %

Question

A

B

C

D

From Students (N = 1491) of Teachers without PS PD

19 22 23 35

765a 358 475 603a

326 239 183 436

201 242 637a 239

198 652a 196 211

51.31 43.73 42.72 40.44

From Students (N = 454) of Teachers with PS PD 62.78 46.56 45.59 46.70

a Indicates the correct answer selection for this question. bPS PD refers to the physical science professional development workshops.

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ASSOCIATED CONTENT

S Supporting Information *

Figure 8. Eighth grade (physical science) CST data; the first cohort of fifth graders who used the atomic models described here entered eighth grade in 2007−2008 (marked with a star).

Notes about the materials required; instructions on how to construct a set of 120 atoms from colored table tennis balls; files to print the periodic table pieces used in this lesson. This material is available via the Internet at http://pubs.acs.org.

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occurred to affect that change. This indicates not only that the students are learning the chemistry in elementary school but also that the understanding persists through at least middle school. The first cohort of fifth grade students taught using the atomic models and lessons described here entered high school in 2008−2009. The first year a portion of this cohort took high school chemistry was in 2009−2010. The CST is also administered to all students enrolled in high school science courses at the end of the year. The end-of-course CST chemistry data indicate that approximately 2.7 times more students were proficient and advanced in 2011 than in 2006 (data not shown). Although it appears that something happened in the district in 2008 that improved test scores at all grade levels throughout the district, this is a phenomenon local to the science data. Investigation of test data in other areas (English language arts, mathematics, and social studies) shows minimal increases in CST scores between 2007 and 2008 for the students examined in this study. During this year, there was a district-wide focus on science, with science professional development provided to all teachers throughout the district who were interested. Further analysis is underway to track students in the initial cohort and correlate this with their performances in eighth grade and high school chemistry.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This lesson was originally developed for a professional development workshop for Rialto Unified School District fifth grade teachers supported by a California Mathematics and Science Partnership (CaMSP) grant sponsored by the California Department of Education. We thank the Rialto Unified School District administrators for their support of the teachers, the teachers and students for helping us refine the original lesson, and Ed D’Souza for having the wisdom to make us a teaching team.

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REFERENCES

(1) See, for example: Rich, R. L. J. Chem. Educ. 2005, 82, 1761−1763. Stewart, P. J. Found. Chem. 2007, 9, 235−245. Seaborg, G. T. Science 1946, 104, 379−386. (2) See, for example: Banks, A. J.; Davis, E. M.; Holmes, J. L.; Jacobsen, J. J.; Kotz, J. C.; Moore, J. W.; Schatz, P. F.; Robinson, W. R.; Tweedale, J.; Young, S. Periodic Table Live! http://www.chemeddl. org/resources/ptl/ (accessed Jun 2013). (3) See, for example: Rayner-Canham, G.; Oldford, M. Found. Chem. 2007, 9, 119−125. Tierney, J. J. Chem. Educ. 2008, 85, 1215−1217.

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CONCLUSIONS Newly developed atomic models have been used in discoverybased lessons that enable learners to construct their own knowledge by exploring the organization of the periodic table, G



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(4) See, for example: Talanquer, V. Chem. Educ. 2005, 10, 95−99. (5) (a) Gordin, M. D. A Well-Ordered Thing: Dmitri Mendeleev and the Shadow of the Periodic Table; Basic Books: New York, 2004. (b) Scerri, E. R. The Periodic Table: Its Story and Its Significance; Oxford University Press: Oxford, 2007. (6) See, for example: Sevcik, R. S.; McGinty, R. L.; Schultz, L. D.; Alexander, S. V. J. Chem. Educ. 2008, 85, 516−517. (7) National Research Council. National Science Education Standards; National Academies Press: Washington, DC, 1995. (8) California Department of Education. Science Content Standards for California Public Schools Kindergarten through Grade Twelve; CDE Press: Sacramento, CA, 1998. See also: California Department of Education. Science Framework for California Public Schools; CDE Press: Sacramento, CA, 2004. (9) State of California Commission on Teacher Credentialing: Multiple Subject Teaching Credential Requirements for Teachers Prepared in California. http://www.ctc.ca.gov/credentials/leaflets/ cl561c.pdf (accessed Jun 2013). (10) California Math and Science Partnership Program grant information available at http://www.cde.ca.gov/PD/ca/ma/ camspintrod.asp (accessed Jun 2013). (11) Mathewson, J. H. Sci. Educ. 1999, 83, 33−54. (12) See, for example, the models available from these vendors: http://www.carolina.com/; https://wardsci.com/; http://www. sciencekit.com/ (all accessed Jun 2013). (13) Fully scripted lessons are available at http://www.csupomona. edu/∼cemast/LessonPlan&Links.shtml (accessed Jun 2013). (14) Gillespie, R. J. J. Chem. Educ. 1963, 40, 295−301. (15) We color-coded the main-group atoms by number of valence electrons to facilitate formative assessment (visual spot checking) by the teacher during the lesson; the paired and lone electrons have different colors for the same reason. (16) Yarroch, W. L. J. Res. Sci. Teach. 1985, 22, 449−459. (17) Organizing data into a data table is a mathematics standard at fifth grade in California. (18) Calif. J. Sci. Educ. 2004, 5 (1). Calif. J. Sci. Educ. 2007, 7 (2). Huddle, P. A.; Pillay, A. E. J. Res. Sci. Teach. 1996, 33 (1), 65−77. (19) Overview description Web page of the California Standards Tests. http://www.startest.org/cst.html (accessed Jun 2013). (20) Web page for text of The No Child Left Behind Act of 2001. http://www.ed.gov/policy/elsec/leg/esea02/index.html (accessed Jun 2013). (21) CEDLT information is available at http://www.cde.ca.gov/ta/ tg/el/ (accessed Jun 2013).

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Discovering Periodicity: Hands-On, Minds-On Organization of the

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