Starting from general to specific, visible to invisible, concrete to abstract in the first question, students were asked to interpret the lines in the atomic emission and absorption spectra. In the second question, they explained some basic terms related to atomic spectra: energy with negative values, discrete energy levels, electronic transition, and photon emission. In the third question, they were asked how the transition of an electron between energy levels is related to the emission of a photon.
In the fourth and last question, students made qualitative reasoning about the behavior of an electron and the resulting atomic spectra in a hypothetical situation where the electron in the hydrogen atom obeys classical mechanics rather than quantum mechanics. During the interviews, participants were requested to think out loud as much as possible.
Each interview took almost one hour and was video recorded. In the data analysis, participants' coherent use of these codes i. For this aim, we focused on how students used the concepts coherently. The proposed mental models are not students' definitions of atomic spectra.
Instead, the mental models were identified by researchers based on inferences from participants' explanations to the features related to atomic spectra described in the questions listed in Appendix I. In the investigation of mental structures, both of the authors discussed and agreed on four mental models summarized in Fig. Interviewer I : Let's look at this. Why do the lines occur?
Why do they have different colors in the visible region in emission spectra? Why are they dark in absorption spectra? Student 8 ST8 : Yes I have. This is umm… In an atom, when an electron with a different n is falling down to the other n level, it emits a photon. For this reason these lines occur.
I : Ok, then, pointing to the emission spectrum in the figure how does this dark area occur? ST8 : This is for example, here, umm…, in this dark area pointing to the emission spectrum in the figure , a photon cannot be emitted. The magnitude of the energy that does not correspond to difference between two energy levels is dark here. Absorption is the reverse of emission. That means, the absorbed photons correspond to dark lines, and other areas are seen colored. One of the important observations about the students displaying this model was the relationship between spectral lines and quantized energy levels.
Another excerpt given below belongs to the other student who explains spectral lines as follows:. I : Is there any relationship between energy levels and the spectral lines? Is the distance between the spectral lines related to the energy levels? ST9 : Energy levels determine the distance between the lines. That means, for example, there are spectral lines. The transition of an electron occurs between the discrete energy levels in an atom and it determines the wavelength of the emitted photon.
As a result of this, the energy difference between two levels pointing to the figure explains lines, and also the distances among the spectral lines. I : pointing to the figure in Question 2 All right. ST9 : Umm… This is the transition of an excited electron to the ground state.
Arrows explain this. It gives the energy as the difference of these energy values. This mental model is the target model for understanding atomic spectra, in which scientific concepts are understood and linked together correctly to explain spectral lines. One of the two students with this model ignored the electronic transitions in an atom in the explanation of spectral lines SL , and considered radiation independent of the behavior of an electron in an atom. More specifically, the emitted photon PE was described as a spontaneous event when energy levels DEL change.
This student's explanation of the emission and absorption spectra is as follows:. I : Let's examine these spectra.
ST1 : Umm… I remember that spectra are as the fingerprints of atoms. It is interesting. I like this description… Probably, the colored lines are because of radiation. I : Why do we see different lines? Why are they lines? ST1 : Line structure is probably because of each color has specific character.
For this reason they are different lines. But I have no idea about they are black in absorption spectrum smiling. I : Let's look at this pointing to Question 2. What does it mean? ST1 : Umm… When an electron is jumping from one energy level to another, umm… For example when jumping from 2 to 1, energy changes due to them.
I : All right!
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ST1 : Energy level changes. There is energy difference between them. Umm… It is radiation.
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Then, we explain spectrum. Because the energies are different, different colored lights emitted naturally. The other student who displayed this model also associated spectral lines with just the change of the discrete energy levels rather than connecting it with electronic transitions.
Furthermore, this student did not understand the energy levels correctly and associated energies with orbits through mathematical manipulations as shown in Fig. ST2 : Yes smiling. I think, an energy level is, here pointing to his drawing , umm, I do not understand that it is the energy of an electron or it is the energy of orbit!
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I do not know…. I : Ok, I am trying to understand what you mean.
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ST2 : From the beginning of the semester, it electron always changes energy levels and photon emitted or we send photon and it also changes energy level. I remember it. I remember from modern physics, but there were similar explanations in the chemistry course. Smiling … Umm… If we get a part from here pointing to his drawing again … Don't we integrate small parts in this way? For example, drawing the integral graph , this is dz smiling … I know this… I am not sure about my knowledge.
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Umm… These lines pointing to energy levels , they are energy levels of electrons. But there is something missing. I feel I am right. However, the missing of BE and ET in the model reflects wrong knowledge organization and incorrect understanding of concepts. Students with PSMAS treated spectral lines as a property of an atom that is not connected to the behavior of the electron or any electronic transition. I : Here are the spectra pointing to the figure in Question 1. First one is an emission spectrum and the other is absorption.
You see the colored lines between nm and nm in the emission spectrum. ST7 : Umm… They are… These colorful lines are energy levels. I : How do you explain, for example, why the dark area between the colored lines is large here and it is small here? ST7 : I am not sure but I think it is because of the difference between energy levels…. I : [Q1: In an emission spectrum, what do the colored lines represent in the visible region , or in an absorption spectrum what do the dark lines represent?