The role of anthropomorphisms in students' reasoning about chemical structure and bonding

In two of the eight sequences analyzed, students produced explanations containing only anthropomorphisms, whereas in the remaining six sequences students also invoked technical as well as anthropomorphic relations. However, the extent to which these two kinds of relations interacted to support the students' emerging explanations differed. In three sequences, the students managed to produce a reasonable explanation through a fruitful combination of anthropomorphisms and technical relations. This is exemplified below in Excerpt 1. In the remaining three sequences however, students managed less well. This is exemplified in Excerpts 2 and 3. In all three examples, we also provide an analysis of what kind of support these students would have needed to carry through with their explanations. This second part of the PEA led to three tentative hypotheses concerning how anthropomorphisms may support students' chemical explanations. On a general level, the analysis suggests that in order to arrive at a chemically satisfactory explanation, these groups would have needed to establish not only further technical, but additional anthropomorphic relations as well.

Excerpt 1: Continuity between anthropomorphic and technical relations

Our first excerpt is an example of how relations to anthropomorphisms interacted fruitfully with technical relations towards an explanation of the chemical concept of electronegativity. In particular, here both kinds of relations reinforced the students' explanations by being clearly tied to each other.

Emma and Julia were trying to solve the chemical problem: Give the approximate values of electronegativity of noble gases, even though you (probably) won't find them in the tables. Argue for your opinion! Before the excerpt began, they had tried to determine the electronegativity values by providing answers which were poles apart: zero and high.

1 Emma: Zero [sounds doubtful]… no… high is not zero…can't you take… if we could have, find out "electron gain energy" [in English] plus "ionization energy" [in English]

2 Julia:    No but you know, it's only to think.

3 Emma: Yeah, it's high… is it, is it enough?

4 Julia:    Well no but…

5 Emma: Is it enough what it says in the answer?

6 Julia:    Yeah, but what we should think about actually, it says "argue for your opinion". It's actually the noble gases, they are very satisfied [laughs] and happy [laughs].

7 Emma: Yeah.

8 Julia:    I mean, they have a full shell… they're cool [laughs].

9 Emma: Yes why?

10 Julia:    Because…

11 Emma: They don't want to let go a single bit.

12 Julia:    No… so it takes a lot of energy to make an ion from a noble gas.

13 Emma: They fight for their electrons.

14 Julia:    Yeah, right… They're among those cool guys [laughs].

Table 1. Summary of the technical and anthropomorphic relations found in Excerpt 1.

Technical relations	Anthropomorphic relations
find out – electron gain energy plus ionization energy
	high value – satisfied – happy
	they – full shell – cool
	they – don’t want to let go
lot of energy – to make an ion from a noble gas
	they – fight for their electrons
	they – cool guys

The starting point for filling the main gap concerning the electronegativity values of noble gases was by construing a technical relation, viz., to the definition of electronegativity according to Mulliken (Turn 1). This relation, being a quantitative measure, seemed not to be considered enough for solving the problem and the students instead turned to the answer given in the handout (Turn 3), which states: "The noble gases have high ionization energies therefore they have rather high electronegativity values according to Mulliken". As the students realized that they needed to argue for the high electronegativity values of noble gases rather than actually provide a value (Turn 6), they began to construe a number of relations to anthropomorphisms, such as high value – satisfied - happy (Turn 6), full shell - cool (Turn 8), and don't want – to let go (Turn 11). Then, in Turn 12, the students returned to the initial Mulliken definition of electronegativity, but this time through the more qualitative, yet technical, relation it takes - a lot of energy - to make an ion of a noble gas. This relation, in turn, was immediately followed by two additional anthropomorphisms, thus closing the sequence.

It is noticeable here how closely the second technical relation was connected to the anthropomorphisms coming before and after. Indeed, the relation is introduced as a further clarification of the two initial anthropomorphisms, evident through the words "No… So…" (Turn 12). And the following anthropomorphism, equally, is added to the technical relation as a confirmation. We may say, thus, that the anthropomorphisms and the second technical relation here were made continuous with each other in the students' reasoning, such that each reinforced the other.

Turning to the second part of the analysis, i.e., what additional gaps or relations could have made these students' explanation even more satisfactory, we may note that the students never explicitly connected the relation in Turn 12 to ionization energy, nor did they establish any explicit relation between electronegativity and ionization energy. Thus, one possible way of helping the students "go all the way", as well as making sure that they actually saw these connections, could be to help them notice an additional gap, viz., by asking "what concept captures the notion of an amount of energy needed to make an ion of a noble gas?", which aims at getting the students to establish a further relation between Turn 12-13 and ionization energy. Filling this additional gap would have closed the students' emerging argument for the connection between high ionization energy and high electronegativity of noble gases given in the answer from the handout.

A first hypothesis emerging from this analysis, thus, is that students may produce strong explanations of chemical phenomena through a combination of anthropomorphisms and technical relations if these are actually made continuous with each other. However, they may need help closing their reasoning with explicit relations to the target concepts of the explanation.

Excerpt 2: Anthropomorphisms for making distinctions between concepts

In our next example, Alice and Linda were engaged in answering the question: What does electronegativity of an atom mean? Contrary to Excerpt 1, here the students never managed to make the anthropomorphic and technical relations continuous with each other and, consequently, never arrived at a satisfactory explanation of the electronegativity concept, either from their own or from a scientific point of view. The sequence started by Alice reading the question constituting the main gap aloud:

15 Alice:   What is electronegativity? … Don't you know that? [laughs].

16 Linda:   I think…

17 Alice:   That it [an atom] wants or doesn't want electrons.

18 Linda:   This was the difference between electronegativity and electron affinity… so electron affinity is the ability and need to attach an electron… electron affinity.

19 Alice:   The opposite [of electronegativity].

20 Linda: Yeah.

21 Alice:   If you have high electronegativity, that's noble gases for instance …which have full shell.

22 Linda:   No, higher electronegativity, for example fluorine and chlorine.

23 Alice:   Why?

24 Linda:   Here it is… [pause]... Exactly, electron affinity.

25 Alice:   Negativity, but then what has…?

26 Linda:   Nitrogen, for example, is equal to zero ["plus minus noll" in Swedish]. Not equal to zero … Right, which question was it?

27 Alice:   Three […] right, that's right. But hey, does a noble gas have low affinity, no, low electronegativity… cause iodine…

[They continue checking electronegativity values for another 21 turns, then change subject].

Table 2. Summary of the technical and anthropomorphic relations found in Excerpt 2

Technical relations	Anthropomorphic relations
	it wants or doesn’t want electrons
…difference between electronegativity and electron affinity…
	electron affinity – ability and need to attach an electron
electron affinity - the opposite [of electronegativity]
high electronegativity… have full shell

The students initially attempted to fill the main gap through an anthropomorphic relation, viz., "electronegativity – wants or doesn't want electrons" (Turn 17). This relation did not seem to be satisfactory and they instead tried to fill this gap through a technical relation to the difference between electronegativity and electron affinity (Turn 18). This relation led to the emergence of a new gap concerning the meaning of electron affinity, which, in turn, the students tried to fill with an anthropomorphic relation (Turn 18). However, this relation also applies reasonably well to the electronegativity concept. Therefore, it did not help the students distinguish between the two concepts. They made another attempt to fill the main gap through yet another anthropomorphic relation (Turn 21), followed by continuing attempts to differentiate between the two concepts of electronegativity and electron affinity (Turns 22–27). However, the main gap about the meaning of electronegativity lingered in these two students' reasoning.

Turning to the second part of the analysis, we may say that if the students had managed to fill the gap concerning the meaning of electron affinity (Turn 18), they would have also been in a much better position to fill the main gap concerning the meaning of electronegativity. Put differently, the effort to complement the anthropomorphic relations with a technical relation between electronegativity and electron affinity could have been a potentially fruitful way to explain electronegativity, assuming that the students had managed to distinguish between the two concepts. One might of course argue that the failure to make this distinction could be blamed on the anthropomorphic relations established by the students to make sense of the two concepts (Turns 18 and 21). However, considering the discussion as a whole, it seems unlikely that additional technical relations or definitions of the two concepts would have helped the students at this point. But what if the students had been supported to continue distinguishing between the two concepts through anthropomorphisms, by being encouraged to construe additional anthropomorphic relations, with the aim of clarifying this distinction in a qualitative manner? In this particular case, the anthropomorphism in Turn 18 could have been more clearly connected to a gap specifically concerning the similarities between electronegativity and electron affinity, and perhaps explicitly developed into the anthropomorphic relation "electronegativity and electron affinity – ability to attach electrons" (cf. Turn 18). Then, the students could have been encouraged to fill a gap concerning the difference between the two concepts, again with the help of current anthropomorphisms. For instance, electronegativity could be related to the ability to "attract" rather than "attach" shared electrons, or the "unwillingness to share electrons equally in a bond", whereas electron affinity could be related to "the tendency for an atom to attach or accept an electron". Finally, after having clarified the difference between the concepts with the help of anthropomorphisms, students could be supported to make these relations continuous with technical ones, such as "how much an atom wants to attract electrons to itself – its electronegativity - helps determining charge distribution in a bond" while "the tendency for an atom to attach or accept an electron – its electron affinity - determines whether a pair of reactants will participate in charge-transfer reactions".

A second hypothesis emerging from the analysis, therefore, is that anthropomorphisms invoked by students may be taken advantage of and developed further, in order to help them better appreciate critical distinctions between chemical concepts, these qualitative renderings of the distinction may be related back to, and made continuous with, more technical definitions of the concepts.

Excerpt 3: Anthropomorphisms for making connections between concepts

Just as Excerpt 2, Excerpt 3 is an example where the students failed to make the anthropomorphic and technical relations continuous with each other. Here, too, the students needed support, not with making a distinction but with clarifying the relationship between two concepts, in this case effective nuclear charge and shielding effect. This excerpt occurred right after Emma and Julia had settled for the answer concerning the electronegativity values of noble gases in Excerpt 1. Next, they spontaneously set out to explain the concept of effective nuclear charge, which they had worked with in the previous problem-solving activity.

28 Emma: But the effective nuclear charge, this, do you remember it? Lower effective nuclear charge.

29 Julia:    Yeah but it has to do with…

30 Emma: It's easier…it's the same thing….but high effective nuclear charge means it also holds on tighter.

31 Julia:    Mm.

32 Emma: But a high shielding number then they willingly let go of electrons. Then they shield.

33 Julia:    No, but it has nothing to do with shielding but only with how.

34 Emma: But effective nuclear charge is atomic number minus shielding.

35 Julia:    Yeah yeah… no, but it's like this, if it has high shielding, then it's easier to take them [electrons].

36 Emma: Yeah, exactly.

37 Julia:    Yeah… I'm just thinking in my head.

38 Emma: It's such an awful lot of different concepts.

39 Julia:    Because then they're so far away so that it's much that's shielding.

40 Emma: Yeah.

41 Julia:    So, they're sort of…

42 Emma: Loose.

43 Julia:    Yeah…they're gone.

Table 3. Summary of the technical and anthropomorphic relations found in Excerpt 3

Technical relations	Anthropomorphic relations
	Lower effective nuclear charge – easier
	high effective nuclear charge – holds on tighter
	high shielding number – willingly let go – they shield

it - has nothing to do - with shielding
effective nuclear charge - atomic number minus shielding
	high shielding – easier to take them
	Far away…much that’s shielding
	They – loose - gone

Initially, two anthropomorphic relations were established for filling the main gap concerning the meaning of effective nuclear charge (Turns 28, 30). Then, a relationship between effective nuclear charge and shielding effect was introduced, first through an anthropomorphic relation to shielding (Turn 32), and then through a technical relation including the formula of effective nuclear charge (Turn 34). In the remaining discussion, the students tried to fill this gap concerning the relationship between the concepts (Turn 34) through a number of additional anthropomorphic relations, such as "high shielding – easier to take them" (Turn 35), and "far away – much that's shielding" (Turn 39). However, the students never really managed to make the technical relation continuous with these anthropomorphic relations, at least not explicitly, and the discussion ended with the main gap lingering.

Turning to the second part of the analysis, we see that if the students had managed to fill the gap concerning the relationship between effective nuclear charge and shielding effect (Turn 34), they would have come a long way towards providing an explanation of effective nuclear charge. As in Excerpt 2, one could argue that the anthropomorphic relations did not appear to help the students to accomplish this. However, also as in Excerpt 2, it seems reasonable to assume that at this point, these students would not have been helped by an outright technical definition of shielding and its relation to effective nuclear charge. Instead, a possible way could be to acknowledge, and even add anthropomorphisms, and then help the students to explicitly connect them to each other and to technical relations. Thus, an additional gap "How does the shielding electrons influence the charge experienced by the outer electrons?"could have been introduced, thereby connecting to the anthropomorphisms already established. In order to fill this gap, the students could then be supported to make the anthropomorphic relations already established in Turns 28, 30 and 35 continuous with each other, specifically, "high shielding - easier to take them" (Turn 35) and "lower effective nuclear charge - easier" (Turns 28 and 30). Then, a more technical gap could be introduced, such as "How does shielding influence the effective nuclear charge?" This gap may be filled by connecting the concepts through both the students' anthropomorphic relations to other anthropomorphic and technical relations in the following manner: "much that's shielding" (Turn 39) - due to the many electrons in the inner orbits - shield the outer electrons from the full positive charge of the nucleus and, so, electrons that are "far away" (Turn 39) and "loose" (Turn 42) - experience or feel less of the positive nuclear charge - refers to the actual or effective nuclear charge.

The third and final hypothesis from the analysis, thus, is rather similar to the second one, and implies that anthropomorphisms invoked by students may be taken further in order to help establish connections between chemical concepts, whereafter these qualitative renderings of the connections may be related back to and made continuous with more technical definitions of the concepts.