STRUCTURAL UNITS AND CHEMICAL FORMULAE

Abstract

Teaching inorganic chemistry for beginners and introducing chemical formulae is not usually supported by structural models, while such models (e.g. the ball-and-stick model) are used in organic chemistry. On the basis of Dalton’s atomic theory, we propose to take sphere packings and crystal lattices as structural models of inorganic solids. Students can develop images of chemical structures and differentiate between molecules and giant structures. Unit cells can be introduced as smallest units of giant structures, and students can derive formulae from given unit cells. Based on the above proposal, a research study was carried out with two classes of grade 8 as the experimental group and other three classes as control group. The experimental group was working for a period of about three months with metals, alloys and their chemical structures, finally with elementary cubes of the cubic structures and their unit cells. Performance in tests, coupled with answers to questionnaires and interviews showed that students of the experimental group were able to recognise unit cells of cubic structures and to derive empirical formulae from the used models. [Chem. Educ. Res. Pract. Eur.: 2002, 3, 185-200]