Understanding metallic bonding: Structure, process and interaction by Rasch analysis

Abstract

This paper reports the results of a survey on senior secondary school students’ understanding of metallic bonding. The instrument was developed based on Chi’s ontological categories of scientific concepts and students’ understanding of metallic bonding as reported in the literature. The instrument had two parts. Part one probed into the students’ understanding of metallic bonding as (a) a submicro <i>structure</i> of metals, (b) a <i>process</i> in which individual metal atoms lose their outermost shell electrons to form an sea-electron and octet metal cations, or (c) an all-directional electrostatic force between delocalized electrons and metal cations, that is, an <i>interaction</i>. Part two assessed the students’ explanation of the malleability of metals, for example, (a) as a submicro structural re-arrangement of metal atoms/cations, or (b) based on the all-directional electrostatic force. The participants in this study included 3,006 Year 10-12 students who were taking chemistry. The instrument was validated by the Rasch Model. The psychometric assessment showed that the instrument possessed reasonably good properties of measurement. The results collected from the instrument revealed that it was reliable and valid for its intended purpose. Analysis of the results revealed that the <i>structure</i>, <i>process</i> and <i>interaction</i> categories of understanding were unidimensional and in an increasing order of difficulty. Implications of the findings for the teaching and learning of the free electron model are discussed.