An example of a teaching analogy:
"The materials used to make the macroscopic models do not reflect the world at the molecular scale. Pieces that represent ions or atoms are bits of plastic or wood that have distinct surfaces and definitive volumes – but ions and atoms do not: they are fuzzy objects more like gas giant planets with their atmospheres slowly thinning out with altitude than ball bearings or marbles or snooker/ billiard balls.
[This atmospheric analogy seems a good comparison (positive analogy) in terms of the nature of the transition – there is no physical 'end' of the earth's atmosphere. However (negative analogy), in terms of scaling, the earth's atmospheric density drops off relatively more quickly than electron density around an atom. (That is, positing a nominal 'top of the atmosphere' is a better approximation, for a planet than positing an 'edge of the orbital' for an atomic electron.) The atmosphere is made up of a vast number of molecules each of which can reach escape velocity (due to the various interactions that can lead to a molecule being on the tail of the Maxwell-Boltzmann distribution) and potentially leave the atmosphere individually, whereas an orbital contains at most two electrons which can only leave if given a sufficient quantum of energy to completely shift elsewhere.]"
Taber, Keith S. (2024) Chemical pedagogy. Instructional approaches and teaching techniques in chemistry. Royal Society of Chemistry.
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