Analysis of the Alternative Conceptions of Preservice Teachers and

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Analysis of the Alternative Conceptions of Preservice Teachers and High School Students Concerning Atomic Size Guluzar Eymur,*,† Pinar Ç etin,‡ and Ö mer Geban† †

Department of Secondary Science and Mathematics Education, Middle East Technical University, Ç ankaya/Ankara, Ankara 06800, Turkey ‡ Department of Elementary Science Education, Abant Iż zet Baysal University, Bolu 14280, Turkey S Supporting Information *

ABSTRACT: The purpose of this study was to analyze and compare the alternative conceptions of high school students and preservice teachers on the concept of atomic size. The Atomic Size Diagnostic Instrument was developed; it is composed of eight, two-tier multiple-choice items. The results of the study showed that as a whole 56.2% of preservice teachers and 59.4% of high school students correctly answered six or more questions out of eight. New alternative conceptions about atomic size, which could be grouped under three main considerations, were found. These alternative conceptions were related to the number of protons, ionic charge, and period and group number.

KEYWORDS: Chemical Education Research, Misconceptions/Discrepant Events, Atomic Properties/Structure FEATURE: Chemical Education Research

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INTRODUCTION At the end of the 19th century, researchers began to deal with students’ misconceptions in science. These are known as “alternative frameworks”,1 “preconceptions”,2 or “misconceptions”.3 Vosniadou states that “science learning is characterized by misconceptions” (ref 4, p 179). Especially after the 1970s, students’ misconceptions in science have been highly investigated.5−9 These misconceptions make more sense for students than scientifically accepted ones from the students’ point of view. Although the misconceptions are not consistent with scientific conceptions, students make use of their prior conceptions to interpret and integrate new knowledge. When this prior knowledge includes misconceptions, its integrative and interpretive function leads to misinterpretation of the new knowledge.10 Therefore, educational research on the identification of misconceptions deserves particular attention. Although much has been studied about students’ common misconceptions related to the atom and its structure, studies on the identification of students’ misconceptions related to atomic size are limited. There is no question that the concept of atomic size is a vital and fundamental concept in chemistry. Developing an understanding of many concepts such as ionization energy and periodic table trends in chemistry mainly relies on learning atomic size. In Turkey, the concept of atomic size is taught beginning in the 9th grade with the periodic table unit; during this period, students are taught about the description of atomic size and the comparison of the size of different elements or their ions. However, students and even © XXXX American Chemical Society and Division of Chemical Education, Inc.

teachers feel that the concept is complicated and teaching of it causes many misconceptions.11,12 In fact, many common misconceptions arise from teachers because they also have similar misconceptions and they have a tendency to transmit their misconceptions to their students unconsciously.13,14 At this level, it is important to identify students’ and teachers’ misconceptions about atomic size. This identification may help raise teacher awareness about misconceptions relating to atomic size. Understanding the concepts related to atom size is important because these concepts are also related to many other chemistry topics, such as periodic trends, ionization energy, and chemical bonding. The concept of the atom is abstract, and instruction of concepts related to the concept of the atom is difficult. Thus, misconceptions related to atoms seem inevitable.15 The reasons students have problems in understanding the characteristics of the atom have been widely studied. Harrison and Treagust investigated 8th−10th grade students’ understanding of models of the atom and reported that many students consider models of the atom as discrete and concrete.16 Osborne and Cosgrove stated that the teaching models about atoms can seem abstract and difficult to relate to daily life.17 In a study with 12th grade students, several misconceptions about the fundamental characteristics of atoms and molecules were revealed by Griffiths and Preston.11 The misconceptions of 13−16-yearold students about matter and the particulate nature of the

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matter were identified by Renstrom, Anderson, and Morton.18 They interviewed 20 students in Sweden and reported that students used the continuous model and could not exactly comprehend the particle model. These studies show that many secondary education students lack both experience with scientific modeling and “intellectual maturity” about models of the atom (p 532).16

concepts in the periodic table chapter. Then, students who want to go into a science field at the university level attend a science track class in grades 10, 11, and 12. However, the concept of atomic size is learned only in grade 9 within the periodic table unit. Students in the sample (grades 10, 11, and 12) took the same course related to atomic size using the same textbooks when they were in grade 9. No additional instruction about atomic size was given before the test, and no points or credits were given for the test. Data were collected from the sample in the 2009−2010 academic years.

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RESEARCH DESIGN AND PURPOSE The main purpose of this study is to determine 10th, 11th, and 12th grade students’ and preservice science teachers’ alternative conceptions about the concept of atomic size. A secondary purpose of this study is to compare the misconceptions that are identified by the students to the misconceptions identified by the preservice teachers. The study was conducted in two phases: (i) development of the instrument applying the twotier, multiple-choice instrument development procedures suggested by Treagust;19 and (ii) conducting the study. The first phase was composed of these efforts: Analyzing the chemistry textbooks that were used in grade 9 on the basis of the current high school chemistry curriculum in Turkey20 to establish the scope of related content of the instrument. Analyzing the relevant literature, and conducting interviews with chemistry teachers, to identify students’ alternative conceptions about atomic size. Developing the 10 multiple-choice items based on interviews with teachers, and students’ alternative conceptions about the concept of atomic size reported in the literature. Conducting a pilot study to observe students’ responses and questions. The chemistry teachers identified students’ responses. Additionally, teachers’ opinions and thoughts were collected about items for the instrument. Revising the first version of instrument based on findings of the pilot study. Designing the Atomic Size Diagnostic Instrument (ASDI) and validating the final version of the instrument. The second phase was composed of administering the instrument in five different high schools and a state university.

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INSTRUMENT In this study, a diagnostic instrument about atomic size, namely, the Atomic Size Diagnostic Instrument, was developed by the researchers. The instrument has eight two-tier, multiple-choice items. The first tier of each item included a comparison question having two, three, or four alternatives, and one correct answer. In the second tier, students were asked to select a logical reason for the answer they had provided in the first part of the instrument.19,21 The ASDI two-tier test was developed based on procedures reported by Treagust.19 First, the scope of the relevant content of the instrument was determined by analyzing the grade 9 chemistry textbook and the current high school chemistry curriculum in Turkey.20 Then alternative conceptions were identified from previous studies,11,16,17,22,23 and from interviews conducted with some chemistry teachers. Before the actual study, the two-tier test was piloted with 104 preservice teachers in two state universities. With the pilot study, the opinions and thoughts of chemistry course instructors were also considered regarding potential students’ alternative conceptions. Some corrections to the instrument were made based on these insights and students’ answers. The Cronbach’s α value measuring the reliability of the test scores in this study was calculated as 0.82. For the content validity, a group of experts in chemistry education examined the test for representativeness and appropriateness of items according to the instructional objectives and students’ alternative conceptions. The test was prepared and given in Turkish. It is translated to English for the present article. The translation of the test was checked by a specialist in linguistics in terms of its correspondence with Turkish. In addition, the same specialist controlled the test with respect to its grammatical aspects and understandability. Finally, the test items were constructed in such a way that each question reflected the students’ alternative conceptions for the concept of atomic size. The ASDI was given to the students during their regular class hour; they were allowed 20 min to complete it. As is the usual procedure for two-tier multiple-choice tests, a student’s answer to an item was accepted as correct if the student selected the correct choice for both tiers.24,25 An English translation of the Atomic Size Diagnostic Instrument is included in the Supporting Information.

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SAMPLE The sample of this study consisted of 174 preservice secondary school science teachers (100 were in the first year, and 74 were in the second year) and 323 high school students (172 11th graders, 98 12th graders, and 53 10th graders) who were randomly selected. Preservice teachers were selected from a state university in Turkey. The first-year preservice teachers take a general chemistry course, while second-year preservice teachers take more advanced chemistry courses, such as inorganic and analytical chemistry. High school students were selected from five different high schools, two of which are Anatolian high schools (106 students) and three of which are general high schools (207 students). Acceptance requirements for these schools differ: while Anatolian high schools accept students on the basis of an exam, general high schools accept students without an exam. Thus, more successful students attend Anatolian high schools. All public high schools in Turkey use the same chemistry curriculum developed by the Ministry of Education.20 All 9th grade students take a chemistry course meeting three times per week; students learn about atomic size

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RESULTS The data were analyzed using Statistical Package for the Social Sciences (SPSS) Release 14.26 The main focus was on descriptive statistics. The following results show that, as a whole, 56.2% of preservice teachers and 59.4% of high school students answered correctly 6 or more questions out of 8. Table 1 shows the descriptive statistics of the responses of the participants. B

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Table 1. Descriptive Statistics of Preservice and High School Students Groups (N)

Min

Max

Mean

Mode

Median

Preservice teachers (174) High school students (323)

1 1

8 8

5.2 5.8

8 8

6 6

Table 3. Alternative Conceptions with Associated Response Combinations Alternative Conceptions

Response Combination

Number of protons

(Q1, B1) (Q2, A2) (Q3, B2) (Q4, D3) (Q6, B1) (Q7, B2) (Q5, B2) (Q6, B2) (Q7, B4) (Q8, A3), (Q8, C4) (Q3, B1) (Q4, B2)

Ionic charge Group and period number

Incorrect response combinations were considered as alternative conceptions if they were chosen by approximately 10% or more of the participants.27 The percentage of these alternative conceptions of preservice teachers and high school students are summarized in Table 2. All of the percentages of correct answers and response combinations are included in the Supporting Information. Similar alternative conceptions were grouped into three categoriesnumber of protons, ionic charge, and group and period numberand are presented in Table 3.

9.6, respectively. Besides these three questions, the fourth question asked to compare three elementsberyllium, lithium, and magnesiumin terms of the group and the period they belong to. A total of 14.4% of preservice teachers and 21.3% of high school students marked the response combination (Q4, D3), which meant that these elements were ordered based on increasing number of protons. In the sixth question, 11.4% of preservice teachers and 10.5% of high school students selected the response combination (Q6, B1), and in the seventh question 10.2% of preservice teachers and 9.7% of students chose the response combination (Q7, B2). With these responses, participants considered that because elements and their ions have the same number of protons, they have the same size as a sodium atom and a chlorine atom. In the sixth and the seventh questions, participants were asked to demonstrate their knowledge of atomic size of cations and anions of elements. This time again, they answered according to the number of protons. All these percentages of responses demonstrate that

Number of Protons

The most common alternative conception among preservice teachers and high school students relates to number of protons. For instance, 13.2% of the preservice teachers and 10.8% of the high school students marked the response combination Q1, B1. Similarly, 10.3% of preservice teachers and 11.2% of high school students selected the response A2 in the second question, indicating that they believed that the atomic size of potassium is larger than that of a sodium atom because potassium has a greater number of protons. This alternative conception is evident in the response combination (Q3, B2) of preservice teachers and students, with a percentage of 10.4 and

Table 2. Distribution of the Percentage of Alternative Conceptions of Participants Alternative Conceptions, %

Alternative Conceptions in Questions The atomic size of a magnesium atom is larger than that of a sodium atom because the magnesium atom has a greater number of protons A magnesium atom has a greater nuclear charge than a sodium atom, so a magnesium atom has a larger atomic size The atomic size of potassium is larger than that of a sodium atom because potassium has a greater number of protons in the nucleus A sodium atom has a larger atomic size than potassium because the attraction per electron by the nucleus is weaker in a sodium atom A nitrogen atom has a larger atomic size than a carbon atom because while nitrogen is in the 5A group, carbon is in the 4A group in the periodic table The atomic size of nitrogen is larger than carbon because the nitrogen atom has a greater number of protons The atomic size of a lithium atom is smaller than a beryllium atom; both of these two atomic sizes are also smaller than that of a magnesium atom because the atomic size only depends on the number of protons The atomic sizes of lithium and beryllium atoms are equal because in the periodic table two of them are in second period; besides magnesium is in the third period, so it has a larger atomic size than both The ionic size of a Mg2+ ion is not equal to that of a Mg+ ion because the ionic charge of a Mg2+ ion is greater, so it has a larger ionic size When a sodium atom loses an electron, the forming Na+ ion has the same size as a sodium atom because two of them have the same number of protons When the sodium atom loses an electron, the forming Na+ ion has a larger size than the sodium atom because the Na+ ion has a greater ionic charge When a Cl atom gains an electron, the Cl− ion formed has the same size as the Cl atom because both have the same number of protons When a Cl atom gains an electron, the Cl− ion formed has the same size as the Cl atom, because the Cl atom only gains electron due to its high electron affinity, so its size did not change When a Cl atom gains an electron, the Cl− ion formed has a smaller size than a Cl because the Cl− ion has a smaller ionic charge The correct trend of size between Cl−, Cl, and Cl7+ is Cl− < Cl < Cl7+ because the size increases in order of increasing nuclear charge The correct trend of size between Cl−, Cl, and Cl7+ is Cl− < Cl < Cl7+ because the size increases in order of increasing quantitative value of ionic charge C

Response Combination

Preservice Teachers, N = 174

High School Students, N = 323

Q1, B1

13.2

10.8

Q1, B4

15.4

12.3

Q2, A2

10.3

11.2

Q2, B4

13.2

12.4

Q3, B1

20.6

16.4

Q3, B2 Q4, D3

10.4 14.4

9.6 21.3

Q4, B2

19.2

19.8

Q5, B2

19.5

13.0

Q6, B1

11.4

10.5

Q6, B2

13.2

12.0

Q7, B2

10.2

9.7

Q7, B3

11.2

9.8

Q7, B4

14.4

15.2

Q8, A3

11.5

12.4

Q8, C4

12.5

13.9

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they had some alternative conceptions about the concept of atomic size. These alternative conceptions could be grouped under three main considerations: number of protons, ionic charge, and group and period number. Response combinations of (Q1, B1), (Q2, A2), (Q3, B2), (Q4, D3), (Q6, B1), and (Q7, B2) reflect the alternative conception that atomic size is mainly determined by the number of protons. Although the attraction between an outermost electron and the protons in the nucleus is described in detail in the curriculum in Turkey, the preservice teachers and high school students could not compare the atomic size of atoms, cations, and anions. The test results showed that preservice teachers and high school students have an incorrect idea about the number of protons, and that they use this idea as the sole deciding factor for atomic size. The second main alternative conception was that atomic size depended on ionic charge and was projected on the items (Q5, B2), (Q6, B2), (Q7, B4), (Q8, A3), and (Q8, C4). These response combinations revealed that some participants had inadequate knowledge for comparison of the atomic size of the elements and their ions. These respondents thought that only the ionic charge value was more effective than the fundamental attraction principles between the outermost electron or shell and the nucleus. The third and the last main alternative conception was that the group and period number stated atomic size, reflected by (Q3, B1) and (Q4, B2) response combinations. These two response combinations have the highest percentage values in alternative conceptions’ percentages of both the preservice teachers and high school students. These results demonstrate that many students misunderstand the relationship between group and period number and atomic size. This misunderstanding might result from rote learning. The trend in some concepts such as ionization energy, atomic size, or electron affinity in the periodic table was taught unconsciously. Students tended to memorize concepts such as “atomic size decreases from left to right in the periodic table” or “atomic size increases from top to bottom in the periodic table”. Yet, reasons for these trends were not known.

many preservice teachers and high school students thought that the greater the number of protons, the greater the atomic size. Ionic Charge

Apart from the number of protons, preservice teachers and high school students commonly selected response combinations based on ionic charge. In the other four questions, the participants were asked to compare how an element’s atomic size changed by gaining or losing electrons. Overall, 19.5% of preservice teachers and 13% of high school students selected the response combination (Q5, B2), where the ionic size of Mg2+ ion was selected as larger than Mg+ ion because the ionic charge of Mg2+ ion was greater and therefore considered to have a larger ionic size. In the sixth question, 13.2% of the preservice teachers and 12% of the students chose the response B2. For the seventh question, 14.4% of preservice teachers and 15.2% of students selected B4, which explained that the atomic size depended on ionic charge when an atom lost or gained electrons. The last question aimed to elicit participants’ conceptions about the order of atomic sizes of an anion, cation, and neutral atom. The results showed that 11.5% of preservice teachers and 12.4% of students chose response combination (Q8, A3) where the selected trend was Cl− < Cl < Cl7+ owing to the fact that the size increased with the increasing ionic charge. In addition, in the same question, 12.5% of preservice teachers and 13.9% of students selected the response combination (Q8, C4) where the selected trend was Cl < Cl− < Cl7+ because of the increasing quantitative value of ionic charge. According to these results, some preservice teachers and high school students selected responses that suggest they think that the greater the ionic charge, the greater the atomic size. Group and Period Number

On the ASDI, 20.6% of preservice teachers explained the atomic size based on group number and chose the response combination (Q3, B1); the percentage was 16.4 for high school students. This meant that some of the preservice teachers and high school students assumed that the greater the group number, the greater the atomic size. Moreover, 19.2% of preservice teachers and 19.8% of high school students selected the response combination (Q4, B2). In this response set, the sizes of lithium and beryllium were assigned as the same because they are both in the second period, while the size of magnesium was assigned a larger size because it is in the third period. This response showed that some preservice teachers and high school students considered that atomic size depended on the period number.

Comparison of Preservice Teachers and High School Students

When the alternative conceptions of preservice teachers and high school students were compared, it was expected that preservice teachers would have fewer alternative conceptions than high school students because preservice teachers take many chemistry courses during their education and learn some relevant topics in a greater detail. However, the analyses of the participants’ responses showed that the mean score of preservice teachers was lower than that of high school students. Before a further discussion of the results, we should mention some caveats of the study. First, in Turkey, at the end of high school, following the 12th grade, students are to take the National University Entrance Examination (LYS) to continue their studies at a university. Hence, 11th and 12th grade high school students work very hard and attend special courses to pass this examination. This study was applied in two Anatolian high schools that accept students after a selection examination at the 8th grade. More successful students choose to study at Anatolian high schools rather than general high schools. These students having studied a great deal for the university exam and having been Anatolian high school students, the mean score of high school students was higher. Second, a hundred of the

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DISCUSSION In Turkey, the concept of atomic size is included in the high school chemistry curriculum of the 9th grade as a part of the unit on the periodic table. Atomic size plays a crucial role in understanding the properties and trends of the periodic table, especially ionization energy. There is a limited number of studies on alternative conceptions related particularly to atomic size. Thus, preservice teachers’ and high school students’ misconceptions about the concept of atomic size were determined using ASDI, and a detailed alternative conceptions list is presented in this study. Although the elimination and source of alternative conceptions are beyond the scope of this work, this study may be used to design effective instructional interventions to address these alternative conceptions. When the ASDI was given to detect preservice teachers’ and high school students’ alternative conceptions, it was found that D

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preservice teachers were in their first year, which meant that they had taken only one general chemistry course at the university. However, preservice teachers who were in their second year took one inorganic chemistry course and one analytical chemistry course. They got higher scores than firstyear preservice teachers and high school students (the mean score of second-year preservice teachers was 6.6). In addition, the study was conducted in a state university that did not require high LYS scores. That is, the state university consisted of students who graduated from general high schools. A study by Tan and Taber28 produced parallel results with this study. They investigated the alternative conceptions about ionization energy of preservice teachers and compared them with high school students.28 They found that the proportion of some alternative conceptions of preservice teachers and high school students was very similar. Moreover, in some cases, the selected response combinations showed that alternative conceptions were more common among preservice teachers.

teachers and high school students. This material is available via the Internet at http://pubs.acs.org.

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Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge many helpful comments from, and fun conversations with, Tuğba Ayas. We would also like to thank Gökçe Gökalp for proofreading this document.

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CONCLUSION AND IMPLICATIONS This study aimed to determine and compare preservice teachers’ and high school students’ alternative conceptions about atomic size. It is found that preservice teachers have similar and even more alternative conceptions than high school students about atomic size, a concept that the preservice teachers will be expected to teach. A number of preservice teachers and high school students do not adequately understand concepts relating to atomic size and the changes of atomic size when an element gains or loses electrons. We propose that teacher education programs should investigate preservice teachers’ atomic size knowledge. The ASDI, which was used to determine the alternative conceptions held, is a useful instrument for such diagnostic aims. Two-tier diagnostic instruments are important tools for monitoring preservice teachers’ knowledge and including curriculum content knowledge in teacher education programs.28 Educators should notice that their students have conceptions that are different from those the educators have. Studies have shown that alternative conceptions can be resistant to change and prevent students from learning new scientific knowledge. Thus, educators should work on how to handle students’ alternative conceptions. They can develop teaching strategies that help students identify their preconceptions and change their alternative conceptions. Also, curriculum materials and teacher education programs may be adapted based on alternative conceptions held by students. In class, teachers may start the lesson with a discussion to see students’ preconceptions. Teachers should encourage students to explain their ideas. Besides these points, teachers should consider that alternative conceptions might arise from language differences. Teachers and students may fail to share the meaning of the terms they use. This study may provide awareness about alternative conceptions of atomic size for teachers, and as a result, educators may address the alternative conceptions students hold about atomic size, and the students’ alternative conceptions may decrease.

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AUTHOR INFORMATION

ASSOCIATED CONTENT

S Supporting Information *

The instrument (ASDI); data tables with the percentage of correct answers and response combination of preservice E

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