Keith S. Taber
Amy was a participant in the Understanding Science Project. The first time I talked to Amy, near the start of her GCSE 'triple science' course in Y10 she told me that "in normal chemistry (i.e., the chemistry part of 'double science', as opposed to the optional additional chemistry lesson as part of 'triple science' that Amy also attended) we're doing about ionic bonding" which she understood in terms of "atoms which have either lost or gained electrons so they are either positively or negatively charged" because "in ionic bonding it's the electrons that are transferred".
When asked other examples of ionic bonding apart from sodium and chlorine Amy told me "That's the one I did".
To a teacher it seems inherently obvious that ionic bonding is type of bonding – in much the way that a snare drum is a kind of drum or a conscientious student is a type of student. However, this may not always be obvious to students (even the conscientious ones).
When I asked Amy about bonding she referred to things being chemically bonded, and when I asked if ionic bonding was the same as chemical bonding, she was not sure how these concepts were related:
So what exactly is bonding?
Erm, where er one thing is joined on to another thing, and it can be chemically bonded or, yeah {laughs}
So we can talk about chemical bonding?
Mm.
Are there other types of bonding then?
Erm, there must be, if there's chemical bonding, I'm not sure, erm
[pause, c.5s]
But we talk about chemical bonding,
Mm.
and we talk about ionic bonding. So is ionic bonding the same thing as chemical bonding or is there a difference?
Erm, in, well in chemical bonding, erm like in a compound, where erm – two or more elements are joined together, that's an example of chemical bonding, but in – erm – ionic bonding it's the erm electrons that are transferred. [pause, c.2s] I think.
It seems Amy had been taught about chemical bonding and had learn about this as "a compound, where two or more elements are joined together", and she had been taught about ionic bonding and had learnt that this was where "the electrons are transferred".
Ionic bonding is not (and need not be associated with) electron transfer. It is not possible form talking to Amy to now exactly what her teacher told her – clearly she could have misunderstood or forgotten material form class. It is possible that it was made clear that ionic bonding was one type of chemical bonding, but Amy either missed that point or did not now recall it. It is also possible is was not made explicit but was assumed to be obvious (especially if ionic bonding had been presented as part of a sequence on chemical bonding. Sadly, what is obvious to teachers is not always obvious to learners, and indeed I've seen in my interviews that students are not always clear when one topic has finished and another has started. There is no sense here that I wish to criticise the teacher (who for all I know gave an exemplary presentation of the chemical bonding), but would simply suggest that when teaching one can never assume what should be obvious is obvious and that it is probably difficult to be too explicit about key ideas, or to reiterate them too often!
So at this point it seemed Amy only knew one example of ionic bonding, sodium chloride, and did not associate this with compounds which had chemical bonding. This could be considered a fragmentation learning impediment – a failure to make a link that was expected from the teaching. I went on to ask her for an example of a compound, and a she told me about sodium oxide I thought this was an opportunity to probe at the association between ionic boding and chemical bonding a little more.
