The octet framework

The octet rule conceptual framework – a common alternative conceptual framework in chemistry

A topic in Learners' conceptions and thinking

Sometimes the terms 'alternative conception' and 'alternative framework' (or 'alternative conceptual framework') are used synonymously. However, it is useful to distinguish between a single conception (a way of thinking about melting, say, for example, that substances only melt at high temperatures) and a network of linked conceptions that tend to be used together and reinforce each other.

An alternative conceptual framework

The octet framework is an extensive set of related ideas that may be found among school and sometimes university level learners.

"This framework includes notions that are incorrect, but also perceptions that would better be described as partial perspectives or limited understandings…

An atomic ontology: atoms as the units of matter — the building block metaphor…

The assumption of initial atomicity…

Ownership of electrons…

Covalent bond as sharing of electrons…

The ionic bond as electron transfer…

The metallic bond…the full shells explanatory principle was invoked

[alternative conceptions about] Stable species…

Use of anthropomorphic language…

The significance of electronic history…

References to ionic molecules…

Electrovalency as the determinant of the number of ionic bonds formed…

Dichotomous classification of bonding…

Bonds [contrasted with] 'just forces'…"

Taber, 1998, pp.601-605

This is represented in the figure:

The idea that chemistry is driven by atoms seeking full shells tends to widely influence student thinking

The central notion of the octet framework is the common alternative conception, the full outer shells explanatory principle.

Read about 'The full outer shells explanatory principle'

The development of the framework also seems to be encouraged by the common 'assumption of initial atomicity' – that is, in thinking about chemical processes as though the reactants are composed of distinct atoms (which is very seldom going to be the case, as the only substances which are usually found in atomic form are generally inert and do not readily react.)

Read about 'The assumption of initial atomicity' alternative conception

One common feature of the framework is the idea that electrons belong to atoms and retains some kind of link to them, even after being removed form the atom.

Read about the ownership of electrons conception

What is common in a common alternative framework?

Every person's thinking tends to be unique – even when superficially similar there are often nuances and subtleties that can be used to distinguish people sharing the 'same' idea.  Whilst is is often reasonable to claim that (for example) 'before teaching four-fifths of people hold a notion that a moving body must be subject t to a force in the direction of travel', when we explore people's thinking about a topic in depth we soon find differences in the details of their thinking.

The octet framework is 'common' in the sense that many learners will adopt it to a significant extent – but not that each of these individuals demonstrates all aspects of the framework (as shown in the figure above).

Indeed when we think about learning, and conceptual change, it seems obvious that no learner will acquire such a framework all at once – they will likely become committed to the central motion the full outer shells explanatory principle, and then as they learn about new aspects of chemistry come ot apply that alternative conceptions in different contexts. So they will build something like the framework above over time. Similarly, when taught the limitations of these ideas, they may find it easier to shift away from some aspects of the framework than others.

One part of the framework that is very commonly held by learners relate to ionic bonding, and indeed in this regard there is a subset of the octet framework, the molecular framework for ionic bonding, which also deserves the term 'framework' as it usually involves several related conceptions that together offer a coherent (if scientifically incorrect) mental model of ionic bonding.

Read about 'The molecular framework for ionic bonding'

Some examples of students’ thinking about the importance of full shells/octets

The following links lead to some postings about student comments related to octets and full outer shells:

 How does the alternative conceptual framework originate?

Clearly the octet rule is a valid heuristic used in chemistry, and in elementary chemistry classes. It seems that some basic ideas taught in chemistry (e.g., species that are stable tend to have octet structures; everything is made from atoms) become developed into a widespread framework fro thinking about key chemical topics. However, more research is needed to explore this, as it seems unlikely so many students would come to the same alternative conceptions spontaneously form reflecting on valid chemical teaching.

So many misconceptions developing from so little teaching? (Version included, with some adaptations, in Taber, 2024)

Sources cited:

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