JOURNAL OF CHEMICAL EDUCATION
A CHART OF CHEMICAL COMPOUNDS BASED ON
PING-YUAN YEH National Taiwan University, Taipei, Form-
FORour freshman course we use Pauling's "General Chemistry,"' in which the partial ionic character of covalent bonds is discussed in terms of the electronegativity scale of elements. The accompanying figure is helpful in enabling students to understand the subject more clearly. In the figure both axes express relative electronegat i d y of the elements. A binary compound is located a t a point, the coordinates of which correspond to the position of its two elements, each along a different PAWLING, L:, "GeneralChemistry,"2nded., W. H. Freeman & Go., San Francisco, 1953, p. 235.
axis. Then it is seen that the chart consists of three regions, i. e., metallic, ionic, and covalent compounds. It should be emphasized that there are no sharp transitions from one type to another; indeed, the chart can be so interpreted. Compounds having bonds of the same partial ionic character-e. g., CBr,, HI, and SiH, -fall on the same oblique line. It should be noted some apparently anomalous locations of polyatomic molecules are inevitable (e. g., BF8 or SiF,). This implies that factors other than electronegativity influence the character of bonds in polyatomic molecules.
