190 Chem. Educator 2011, 16, 190–194 Students’ Alternative Conceptions about Atomic Properties and the Periodic Table Issa I. Salame*,†, Samema Sarowar†, Sazea Begum† and David Krauss‡ † Chemistry Department, City College of New York, CUNY, 160 Convent Avenue, New York, NY, 10031, salame@sci.ccny.cuny.edu; ‡ Department of Science, Borough of Manhattan Community College, CUNY, 200 Chambers Street, New York, NY, 10007 Received February 17, 2011. Accepted July 12, 2011. Abstract: Students possess countless alternative conceptions about chemistry which are related to the fact that students bring to chemistry views, theories and explanations that are different than those held by scientists. Students resist changing their views and explanations in conventional teaching or lecturing classrooms because the teacher-centered courses do not always cause conceptual change as they do not address the basic principle that knowledge is constructed in the mind of the learner. Participants of this study are CCNY students who are enrolled in the second-semester of general chemistry during the spring of 2009. The course contains about 240 students who have completed General Chemistry I. The methodology included a two part question on an exam followed by interviewing students for further clarification and understanding of their reasoning. The data show that the majority of students, 80%, do not understand atomic radius trends, they held onto their alternative conceptions and could not answer a simple question related to those trends. Of those who answered correctly, 62% chose the answer based on rote memorization and could not provide an acceptable scientific explanation. Introduction Students possess countless alternative conceptions about science in general and chemistry in particular. These alternative conceptions are related to the fact that students bring to science views, theories and explanations that are different than those held by scientists. These alternative conceptions are developed at the early stages of education and an individual keeps building on their alternative conceptions. Concepts that the students build about the atomic properties could be aligned with what is scientifically agreed upon or can differ from it. In this paper, we will refer to those that differ as alternative conceptions [1]. In spite of those alternative conceptions, students rely on algorithms to solve problems. Misconception or alternative conceptions is defined as [2] any concept that differs from the commonly accepted scientific understanding of the term. Nakhleh also states that, “Once these misconceptions have been integrated into a student’s cognitive structure, these misconceptions interfere with subsequent leaning. The student is then left to connect new information into a cognitive structure that already holds inappropriate knowledge.” The alternative conceptions that students develop can hinder their conceptual understanding. Conceptual understanding ensures that a student will not forget the material that they have learned. Whereas memorization of a method to solve a chemistry problem will be forgotten as soon as the course is complete. Once students have these alternative conceptions it is difficult to change it. Science education research [3] has found that young children develop intuitive ideas and beliefs about natural phenomena. As they learn more about the natural world they develop new or revised concepts * Address correspondence to this author. Chemistry Department, City College of New York. ‡ Department of Science, Borough of Manhattan Community College. † based on their interpretation of this new information from the viewpoint of their existing ideas and belief. If students encounter new information that contradicts their alternate conceptions it may be difficult for them to accept the new information because it seems wrong. For this reason instructors should try to address briefly the concepts behind the algorithmic problems which could improve students’ conceptual understanding of the topics. Some students resist changing their views and explanations in conventional teaching or lecturing classrooms. Researchers [4] also found that students in science and math have been consistently trained algorithmically, rather than conceptually. Therefore, when exposed to a different type of instructional and assessment method, students tend to be resistant. The reason teacher-centered, lecture-based courses, do not cause conceptual change is because they do not address the basic principle that knowledge is constructed in the mind of the learner [5]. One of the earlier papers in chemistry education research [6] speaks about how most educators see solving chemical problems to be the major behavioral objective of freshmen chemistry. It also showed that textbooks were written from this point of view, and this may be what establishes the supreme importance of numerical problems in student minds. Science educators [7, 8] have found that students were able to do algorithmic problems but struggled with answering conceptual problems. Their studies found that many students could not use chemical concepts to solve conceptual problems. Also the results of Nakhleh’s studies found that conceptual problem-solving ability lagged far behind algorithmic problem solving ability. Once again memorization is the skill that students utilize to solve problems because that is the way they have been instructed. Work by Nakhleh and Mitchell [8] states, “It does not seem that presenting an algorithm and demonstrating the myriad of problems that can be solved using that algorithm facilitate understanding of the underlying © 2011 The Chemical Educator, S1430-4171(11)12375-0, Published 07/19/2011, 10.1333/s00897112375a, 16110190.pdf Students’ Alternative Conceptions about Atomic Properties and the Periodic Table concept.” Other researchers offer an explanation for why some students choose to memorize rather than develop a conceptual understanding. For example, work done by Bunce illustrated that students enter chemistry classes with many insecurities and fears about their ability to be successful in chemistry [9]. And these fears often result in students choosing memorization rather than understanding as a way to succeed and earn an acceptable grade. The lack of conceptual understanding inhibits students from performing to the best of their abilities. In one study [10], the results showed: “… success on algorithmic questions was always higher than on conceptual questions, verifying the results of previous studies. Additionally, the students with better reasoning ability outperformed students with poorer reasoning ability on all question types, and the scores of the better reasoners were significantly higher than those of the poorer reasoners on three of the four conceptual questions administered.” If students possessed better reasoning skills, which are based on a thorough conceptual understanding, then students would perform better on not only algorithmic problems but also conceptual problems. Cognitive research shows that when students construct their own knowledge they achieve a better conceptual understanding of chemistry [11]. Bodner states that “Knowledge is constructed in the mind of the learner” [5]. During the learning process, students use their experiences and knowledge to construct an understanding and achieve sense making. This process is facilitated by the interactions they have with their instructors and peers, which present conflicts of thoughts and ideas that help students modify their thought processes [12]. Concepts that the students build about the atomic theory could be aligned with what is scientifically agreed upon or can differ from it. The following research questions will be addressed as part of this study: 1. 2. What types of alternative conceptions do students possess about atomic properties and periodic trends? What is the role of mnemonic use, regurgitation, and memorization in answering questions about periodic trends? A paper and pencil questionnaire, which is included in as part of the in-class assessment, will be used to collect initial data. These data will then be used to guide the question in a semi-structured interview. In this interview, a student is asked to elaborate on their answer, provide an explanation, and discuss their thought process as they arrive at the answer. The interviewer does not lead the student just elicits information. This information can be used to determine the source of the alternative conceptions, their type, how deeply embedded in the cognition process, and how these misconceptions hinder further learning. Context of the Study The research goals of this study are to identify alternative conceptions that students hold about various topics in general chemistry. Participants in this study were students enrolled in second-semester general chemistry at an urban four-year college. All students participating in the study had completed the first semester of general chemistry. The data collected to support our hypothesis that the majority students do not Chem. Educator, Vol. 16, 2011 191 possess an in depth conceptual understanding of atomic properties and periodic trends and this issue should me addressed by chemistry educators at the high school level, as well, as the college level. The research question is: “Which element has the smallest atomic radius? Provide an explanation for your answer.” We inserted the question that our research is concentrated upon, in a routine exam taken by general chemistry students. Rubric Development and Results The data were collected to examine the type of responses that we would get and to help in the creation of a rubric. A rubric would help us sort the data in manageable groups. We attempted to look for patterns in the explanations that were provided. The preliminary data that were collected, during the month of October of 2009, helped in providing the needed information for a rubric and to guide the design of the interviews that were held during the month of December of 2009. Majority of the students’ answers, 80%, provided an unacceptable scientific explanation. Students indicated that helium had the smallest atomic radius and then proceeded to draw a rough periodic table which showed atomic radius decreasing from left to right and from bottom to top. Based on answers provided by the students, we then came up with a rubric ranging from a score of 1 to 5. A score of 1 indicates inadequate conceptual understating and a score of 5 indicates complete conceptual understanding. This rubric sorts the answers into a number scale based not on the right or wrong answer but the understandings behind the concepts. A complete conceptual understanding would not only provide the correct answer but also an explanation that shows a full understanding of effective nuclear charges. Smith and Metz point out how students often learn how to solve mathematical problems without understanding the chemistry [13]. They memorize chemical definitions and use chemical terms without true comprehension. Researchers in Turkey argue that, “The analysis of written responses showed that many students tend to leave the explanation section of the questions blank or repeat some sort of statements from the questions rather than giving any detailed reason [14]. The written responses showed that at all levels, many students were unable to use particular ideas.” Even though many students knew that helium had the smallest radius they were unable to demonstrate why. They mostly resorted to rote memorization of periodic trends as an explanation for their answers. We also wanted to observe the knowledge that students possessed of effective nuclear charges, for this is an important factor that aids in determining which elements has the smallest radius and plays a role in understanding atomic sizes, periodic trends, and electronegativity. The data that we collect helped us to create several guided questions for the interviews. These interviews were openended and impromptu. We attempted to ask questions that would help students elaborate on their answers. We did not want to provide the students with the correct answer, we only wanted to collect data on what the students’ perception and understating is of their answers. Open-ended interviews allowed us to follow the students’ train of thoughts giving us insight into their thought processes. © 2011 The Chemical Educator, S1430-4171(11)12375-0, Published 07/19/2011, 10.1333/s00897112375a, 16110190.pdf 192 Chem. Educator, Vol. 16, 2011 Salame et al. Table 1. Rubric Developed for the data analysis Score 1 Inadequate Conceptual Understanding Response Characteristics Example Provides an incorrect answer. Explanation offers no conceptual understanding of effective nuclear charge or no explanation is provided at all. Hydrogen. Hydrogen is a gas so it is smaller than all metals, it only has one orbital 1s and it has the smallest molar mass. Provides a correct answer based on memorization of periodic trends. Or provides an incorrect answer with an explanation that has little understanding of effective nuclear charge. Helium. One of the trends of the periodic table is that the atomic radius of an element increases as you go down the periodic table and to the left. Therefore the smallest element would have to be the one that is the most to the right and top of the table. 3 Approaching Conceptual Understanding Provides a correct answer. Explanation shows some understanding of effective nuclear charge. Helium. Since it has 2 protons compared to 1 proton in H it has more + charge that pulls electrons thus has the smallest size. 4 Acceptable Conceptual Understanding Provides a correct answer. Explanation shows good understanding of effective nuclear charge. I would say smallest element in radius is Helium. We know that atomic radius decreases as we move along the periodic table since the positive attraction effectuated by the nucleus increases, pulling the electrons closer. This reduces the radius. The smallest radius atom must have the least number of electron shells, but the greatest protonic positive charge. Our only two contestants are H and He. Since helium has one more proton than hydrogen but also has its electrons in 1s it must be the smallest element. Provides a correct answer. Explanation shows complete understanding of effective nuclear charge. Diagrams are provided to supplement their explanation. There were no students who received a score of 5. 2 Minimal Conceptual Understanding 5 Complete Conceptual Understanding 90 Percentage of Respondents 80 70 60 50 40 30 20 10 0 1 2 3 4 5 Score Figure 1. The percentages of responses of each answer based on the rubric evaluation. Results We were able to analyze the data that were collected and gained insight on the type of answers that students provided. The graph shown in Figure 1 is based on the rubric. There seems to be some confusion between the atomic mass and atomic radius as illustrated by the following response: “Hydrogen. Because hydrogen has the smallest atomic mass of any other element in the periodic table.” Some of the students related the number of electrons to the atomic radius: “It has the smallest radius and the least amount of electrons and therefore takes up the least amount of volume.” It is noteworthy that hydrogen was the most common incorrect answer with 78% of incorrect responses. Other students who relied on regurgitation, recall, and mnemonic use still ended up with incorrect answers, and some made them up as they went along: “As you go from right to left the atomic radius decreases. As you go from bottom to top the atomic radius also decreases and H has the smallest molar mass weight.” Francium was the second most common incorrect choice, with 14% of incorrect responses, which we found to be surprising. It is easy to see why students will choose hydrogen and try to reason it, but it was peculiar that they choose francium. Here is an example: “Francium. Metals are smaller in size than non-metals are Fr has the most metallic characteristics according to the periodic table of elements. A majority of the students who picked helium as the smallest element in the periodic table provided an explanation that is not consistent with what is scientifically accepted or was based on regurgitation, mnemonic use, coincidence, or guessing. Here is an example of guess work and incorrect explanations: “Helium. The column it is in, it is a gas.” Many students relied on regurgitation and mnemonic use to arrive at the correct answer and provided the mnemonic use as a scientific explanation. For example: “Helium is the element farthest from the bottom left (in which direction of atomic size increases.” Figure 2 clearly shows that when students try to answer questions about the periodic table and its properties, they resort to regurgitation and mnemonic use such as the diagram in Figure 2. This diagram was not uncommon and many students drew this diagram as a scientific explanation for the atomic size question. The following student used regurgitation to figure out the atomic radius question and then disregarded the answer, helium, and went with hydrogen because it made more sense. “It is Helium, because as you move to the right and towards © 2011 The Chemical Educator, S1430-4171(11)12375-0, Published 07/19/2011, 10.1333/s00897112375a, 16110190.pdf Students’ Alternative Conceptions about Atomic Properties and the Periodic Table Figure 2. An example of a scientific reason about the atomic sizes. the bottom of the periodic table, the number of electrons increase which means that the radius also increases. So the smallest element with the smallest radius would be the one to the far right and all the way at the top of the periodic table, which is helium, however because hydrogen has one less electron than helium, hydrogen is the one with the smallest radius”. Discussion Identifying misconceptions that students have and addressing with in our instruction can help students to develop a better conceptual understanding. Chemistry education researchers bring up a possible explanation for why some students have certain alternative conceptions [15]. Tyson’s studies found that language emerged as a key factor in the development of students understanding of chemical equilibrium; we need to be alert to terms that are subject to misinterpretation by our students. Chemistry education research has helped identify many alternative conceptions that students have. According to one of the leading figures in chemistry education [16]: “Although chemistry education researchers have identified common misconceptions for almost every topic taught in introductory since courses, probably nine out of ten instructors are not aware of these misconceptions or do not utilize ways to counteract them in instruction.” Identifying students' alternative conceptions will provide instructors with an opportunity to cause conceptual change and to help students construct a clearer understanding of important concepts. Memorization is not a growth in knowledge; it is at times just short-term retention. Our preliminary analysis of the data collected for the purpose of creating the rubric suggested that students do not posses conceptual understanding of atomic trends such as atomic radius. One student answered the study question by drawing the periodic table and indicating, with arrows, how atomic radius decreases. Some students use memorization of the periodic trend to justify their answer, but because they lack the conceptual understanding they were unable to reason why helium has the smallest radius instead of hydrogen. If they were able to visualize electrons orbiting around the nucleus and understood effective nuclear charge and electrostatic force it may have been possible for them to reason out why helium has the smallest atomic radius and not hydrogen. They were only able to spit out memorized information, which shows no conceptual understanding. Chem. Educator, Vol. 16, 2011 193 Some of the answers that lacked any sort of understanding, relied only on memorization, or were based on intuition or pure guessing. Answers such as, “Hydrogen weighs the least and it has only one valence shell”, indicate that this student was tossing around terms. There were also many answers that said, “Hydrogen has the smallest atomic radius because it has the smallest atomic mass”. This was the most frequent answer provided. Students were using intuition to answer, because they reasoned out that something that has the smallest atomic mass must also have the smallest atomic radius. Another student drew out two images, one of a hydrogen atom and another of a helium atom. They drew out the electrons circling the nucleus, indicating that electrons were repelling each other, while being attracted to the proton. Some students’ responses show confusion about periodic trends for atomic radius. Instead of thinking that atomic radius decreases left to right and bottom to top, they thought that atomic radius decreases right to left and top to bottom. These students answered francium to be the element with the smallest atomic radius. Rote memorization of periodic trends resulted in such answers. They memorized the periodic trend but were unable to recall it properly. One student that indicated francium as the answer wrote, “As the amount of electrons increase the force of attraction is greater between the proton and electrons. So the radius gets smaller”. Answers based of rote memorization show lack of conceptual understanding. We should note that our interview results only confirmed our findings. Recent work done says that the teachers need to be trained to diagnose students’ alternative conceptions, design interventions using particle-level animation, access the animation through textbook publishing companies, free digital libraries, or commercial software suppliers, and make them accessible to their students [17]. If teachers are not able to catch these misconceptions then they will not be able to address them. Conclusion The alternative conceptions about the atomic properties and periodic trends were reflected in the written answers that the students provided on the exam. Our preliminary results show that the students who have completed “General Chemistry I” and studied atomic properties and periodic trends show lack of understanding of the topics. Students used memorization and pointed arrows to answer questions about periodic trends. This lack of understanding and reliance on memorization to learn science could continue with them throughout their college education. Chemistry topics especially the atomic properties and periodic trends should be presented in a scientific context and students should be part of the learning process. Teaching for an in depth understanding in “General Chemistry I” classes would provide a pipeline of future successful scientists and researchers. It is our hope that understanding this phenomenon will help instructors improve their teaching methods and thus improve student understanding. References and Notes 1. Driver, R.; Easley, J. Studies in Sci. Educ. 1978, 5, 61–84. 2. Nakhleh, M. B. J. Chem. Educ. 1992, 69, 191–196. 3. 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