An example of a common alternative conception:
It is very common for learners to think that chemical reactions occur so that atoms can fill their outer electron shells, or acquire outer shell octets (which is the same thing for elements in period 2). This is a both a common notion, and one that can be hard to overcome. Students will often continue to think this way even after being taught about energetics (bond enthalpies, free energy changes).
Most of the exampes of chemical reactions met in introductory chemistry classes do produce products that contain ions that do have noble gas configurations (usually outer shell octets) or molecules where the atoms can be considered to have octets in their outer shells (or two electrons for hydrogen atoms). This may seem to reinforce the alternative conception – except, of course, the reactants in those same reactions also usually meet this same criterion.
It does not make any sense to suggest, for example, that hydrogen reacts with fluorine or methane burns in oxygen in order to give produces with octets/full outer shells, when the starting materials already meet that criterion. But, that does not stop many learners making this argument!
This 'full outer shell explanatory principle' is part of the octet framework that dominates many learners' thinking about atoms and molecules and chemical processes.
Read: The octet rule conceptual framework – a common alternative conceptual framework in chemistry
Read: Conceptions of the octet rule
Read about a diagnostic probe for use in teaching: Why do hydrogen and fluorine react?
[Please be aware that a word may have different nuances, or even a different meaning, according to context.]« Back to Index
