i.e. ways of presenting the scientific content in different stages of production and under different
syntactic formats. In our work with teachers, the scientific enterprise is depicted as
an aim-driven, value-laden transformation of the natural world mediated by conceptual
and material tools; in such depiction, theoretical models are given a central
role. The paper presents a didactical (i.e. instructional) unit with such conceptualisation
of NOS; this conceptualisation is set against the backdrop of some scientific
narratives on the history of the atomic theory that are embedded in the unit.