Conservation of force: sharing-out of nuclear charge
Alice (17 year old college student, a participant in the Physical Science project) appeared to hold the common notion (Taber, 1998) that nuclear charge was shared out among electrons, so on ionisation,
“you’ve got the same number of protons, or if you like positive charge from your nucleus, as you have before, but then you’ve got a different number of electrons that it can effect, and it’s fewer, so, it should balance out that each of these electron have got more charge effecting them”.
This is an alternative conception relating to forces which appears to be common among students, and seems to derive from intuition about how the world works, i.e. as if in an atom each proton is responsible for attracting one electron (or because it has a 1+ charge, has the capacity to attract a single negative charge). Potentially this may derive from implicit processing in the cognitive system, that is how our brains undergo preconscious processing, such as pattern recognition, which occurs before conscious awareness of what we are thinking, i.e. our tacit knowledge. (Note: this type of cognitive feature has been called a 'phenomenological primitive', or 'p-prim'). Such perceptual features can sometimes act as grounded learning impediments, as they channel the way learners interpret teaching, leading to understanding at odds with scientific knowledge.
This particular alternative conception is linked to the way learners commonly (a) see forces as from one body to another (rather than being two-way interactions), and often fail to make the distinction scientists make between the force itself, and its effect(s).
Reference: Taber, K. S. (1998). The sharing-out of nuclear attraction: or I can’t think about Physics in Chemistry. International Journal of Science Education, 20(8), 1001-1014.
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Dr Keith S Taber kst24@cam.ac.uk
University of Cambridge Faculty of Education