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.
Can you tell me what you think that's meant to represent?
Er, two hy-, a hydrogen molecule, 'cause it's like they've got one electron, in the only one shell, and they're joined together, a covalent bonding, and they're sharing it.
So what is a covalent bond exactly?
When they share electrons.
When you share electrons?
Yeah.
So when Umar thought of covalent bonding he seemed to primarily associate this with the notion of 'sharing' of electrons. The idea that atoms can 'share' anything could be considered an example of anthropomorphism, but this is a common metaphor that is widely used in discussing bonding.
The 'sharing' notion is however little more than a descriptive label, and has limited explanatory power. Acceptable explanations of the bond would draw upon scientific concepts, such as electrical forces, or atomic orbital overlaps allowing the formation of lower energy molecular orbitals. I probed Umar to see how he understood the nature of the covalent bond.
Or do you think they're stuck together?
I think they're quite strong together, covalent is quite a strong bond.
So that will hold them together will it?
Yeah.
Umar certainly saw the bond as a strong linkage of some kind, but so far my questions had not revealed how he understood the bond to hold the molecule together.
Well how does it do that?
It's like, they're joined together, 'cause first of all they just had two atoms with one electron each, and now they're sharing two electrons between them. So it's quite strong.
Oh, why's that?
Because the the the actual, when they share them they're like combined into like one sort of whole thing, instead of two separate atoms.
Right, so the, so the bond, which is the sharing of two electrons, that holds them together,
Yeah.
to make one thing, which we've called a molecule.
Yeah.
So at this point in Umar's course he seemed to conceptualise the covalent bonding as electron sharing and saw the action of sharing to inherently hold the molecule together, and seemed to be satisfied with that as an explanation for the bond. This 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 (see Sharing the same shell and electron makes them more joined together like one)*.
