Comments on: All Models Are Wrong in Chemistry! (And In All Science)

By: Miquel Solà

Miquel Solà — Sat, 17 Jan 2015 05:54:28 +0000

Personally I like very much the following sentence by Dewar:

“The only criterion of a model is usefulness, not its “truth””

M. J. S. Dewar, JACS 106 (1984) 669

By: Lloyd Carroll

Lloyd Carroll — Fri, 16 Jan 2015 17:00:01 +0000

Unfortunately, some scientists who work in rigorous areas in the fields of mathematics and physics, for example, seem to occasionally take umbrage with the qualitative nature of many of the models used in Chemistry. I know of one physicist/engineer who refers to Chemistry as “the class where you learn things that can’t possibly be true”, or “where you go to unlearn what you just worked hard to learn.”

In some ways, these people have a point – for instance, we teach students the octet rule, then explain that it doesn’t provide a framework the magnetic behavior of diatomic oxygen. Or we teach broad features of orbital structure and filling (Aufbau principle and such), then proceed to explain to students that the rules/guidelines we just gave them don’t work for all elements – there are a whole list of them that have a different electron configurations than are predicted by the Aufbau and pauli exclusion principles.

Personally, I do not find myself bothered by such examples – I look at these models (“incorrect” though they might be) as incrementally (and sometimes, exponentially) more complex, and more complex models allow for a greater understanding of nuance and variation. The learning of a simple model provides a cognitive space for a student, which can then be refined and enhanced in developing understanding of more complex behaviors. This is normal, this is learning, and to develop deeper understanding successfully requires thought and careful consideration.

By: Yessica

Yessica — Fri, 09 Jan 2015 04:42:26 +0000

In reply to Mike Ryan. I agree. As a chemistry undergrad, I am aware that several of the models we use to understand fundamental chemistry are technically incorrect. But they have persisted because they are easier for someone at our knowledge level to understand/internalize. I can't really think of any clear way to avoid that, considering that people struggle enough in class as it is.

By: Mike Ryan

Mike Ryan — Thu, 01 Jan 2015 22:12:41 +0000

Many good points. Le Chatelier and Markownikoff are two examples that come to mind of methods that work but whose “story” has little basis in fact. The idea of the reagents trying to restore an equilibrium position gives the right answer but conjures up the picture of some kind of molecular debating chamber where decisions to favour the endothermic reaction are made so that the temperature can be reduced to re-establish the status quo.

Thanks for promoting discussion. It is good to re-examine how we as teachers see the chemistry so that we can minimise the misconceptions we set up for students.