Keith S. Taber
Umar was a participant in the Understanding Chemical Bonding project. When I spoke to him in the first term of his advanced level chemistry course he identified figure 2 (below) as representing a hydrogen molecule, with covalent bonding.
Sharing the same shell and electron makes them more joined together like one
Umar was a participant in the Understanding Chemical Bonding Project. When I spoke to him in the first term of his advanced level chemistry course he identified figure 2 (below) as representing a hydrogen molecule, with covalent bonding.
Umar suggested that covalent bonding is when atoms share electrons to combine into one whole thing. That discussion took place early in the interview, before we then discussed a whole range of other images. Near the very end of the interview I returned to ask about figure 2 again.
Interviewer: And number 2 was what kind of bond?
Umar: Covalent.
I: Now, what holds the molecule together in number 2?
U: The two electrons – shared.
I: And how does that hold them together?
U: 'cause they're sharing the same – shell and electron.
I: And why does that hold them together?
U: Makes them more, together like, makes them more like joined together like one.
After we had first discussed what this image was meant to represent early in the interview, Umar discussed a wide range of other images, and in the context of some of these he discussed bonding in terms of forces and electrical charge. As he had not mentioned such notions in the context of figure 2, even after using the ideas elsewhere, I sought to see if he recognised that forces were acting in the hydrogen molecule.
I: I see. Is there any force there holding them together?
U: It's, erm could be the charges of the electrons and the charge of the nucleus.
I: Would the nucleus have some sort of interaction with the electrons – some sort of attraction or repulsion?
U: Yeah.
I: Would it be attraction or repulsion?
U: Erm, attraction.
I: So which electron does this nucleus attract.
U: Erm, it attracts both of them, and the other one attracts both of them because they are both, like, opposite charges. So that's why they are like, around there. It might be like they move around. Around that part.
I: So they might actually move about?
U: Yeah.
I: I: But you think the two nuclei attract the two electrons?
U: Yeah.
I: Do the two electrons attract the two nuclei?
(Pause, c.3s)
U: Yeah, think so, the – yeah.
I: Yeah? Do the two electrons attract each other?
U: No, they repel.
I: Do the two nuclei attract each other?
U: No they repel.
So it seemed that Umar understood the forces acting in the covalent molecule but that these ideas were not readily cued in that context even though he readily used the idea of forces between charges to explain other kinds of chemical bonding. In the context of covalent bonding however, the notion of the bond as electron 'sharing' was cued instead. Arguably the notion of the covalent bond as sharing of electrons acted as a grounded learning impediment perhaps blocking him bringing to mind alternative ways of thinking about the bond. This could be seen as an example of weak anthropomorphism: the idea that the electrons were 'shared' stood in place of a more scientific explanation of the bonding process.
