A NEW PERIODIC CHART To the Editor
direction) = analogy in periods or period relationship (e. g., iron period, Mn, Cr, etc.). DEARSIR: This empirical relationship is now borne out by the I read with great interest the article on "A New concept of atomic structure: elements in the upper Periodic Chart" by John D. Clark [J. CHEM.EDUC., half add electrons to the outermost shell, elements in 10, 675 (Nov., 1933)l and note with disappointment the lower half add electrons to the next inner shell (in that the author has left out all the elements from Ce 58 the case of the rare earths, to the second inner shell)to Lu 71, contenting himself with naming them the hence their great similarity. In other words, beginning "rare earths," thereby losing an opportunity of stress- with Sc the M shell is being filled to its full capacity. ing the "new" principle regarding the periodic system. which is reached with Ga. Similarly, with Y, La, and With this omission the chart is similar to one pub- Ac the N , 0, and P shells are respectively filled, while lished in 1918 [Astrophys. J., 48, 241 (Nov., 1918)l with Ce the 0 shell is beginning to be filled from 18 up and since then repeated with several additions, as to 32 electrons, although the P and Q shells have 8 and in the "Chemical Dictionary" (Philadelphia, 1929, p. 4 electrons, respectively. 544). I n the spirals this is indicated by using a dotted line The really "new" principle regarding the periodic for the upper portions and a solid line for the lower system was stated in 1918 [J. Am. Chem. Soc., 40, portion. In the modified table (e. g., "Chemical Dic1023 (Aug., 1918) and Am. J. Sci., 46, 481 (Sept., tionary," p. 545) the elements in the upper half are 1918)l and formulated empirically as: the properties of placed in vertical groups, those of the lower half in the elements in the upper half of the spiral (or modified horizontal groups, thereby stressing the principle of table) are similar along the vectors (or vertical direction group-relation and period-relation. of the table) = analogy in groups or group-relationship INGO W. D. H A C ~ (e. g., halogens, etc.) while the properties in the lower COLLEGE OF PHYSICIANS AND SURGEONS S ~ FRANCISCO, N CAL~ORNL~ half are similar along the periphery (or in a horizontal
