LETTERS T h e Periodic (?) Table
few attempts to actually change the law in the light of more recent knowledge. It is hardly scientific to To the Editor: maintain that Mendeleeff's original statement is One of my students asked me the other day: "Is it sacred and subject to no modification whatever forevertrue that the periodic law has been discarded as ob- more. solete?" He had just been reading the paper by W. F. The only concrete difficulty Professor Cadbury Luder in the January issue of this JOURNAL entitled mentions is that "the resemblances between magnesium "Electron Configuration as the Basis of the Periodic and zinc and between sulfur and chromium, as shown rable." Since I was already somewhat irate on the by sulfates and chromates, are not so much as sugsubject of this paper, the remark induced me to gested in this chart." This objection is conclusively write this letter. answered by a glance a t the chart, where it is perfectly Among the reasons for my irritation was my belief obvious that both chromium and sulfur have six that there have been too many pet "periodic charts" valence electrons and that magnesium and zinc have published in recent years, including the same chart by two. Furthermore, the chart immediately makes the same author in this JOURNAL in 1939. Another plain the reason why chromium does not have a valence reason was the optimistic claim made for the merits of of minus two as sulfur does! this latest chart: "The chart . . . overcomes all . . . the When the chart was first proposed in 1939 (based on defects . . without introducing any new difficulties." Ebel's suggestion in this JOURNAL) I was not aware of Among the new difficulties which occur to me is the Gardner's chart published in Nature in 1930. Gardner fact that the resemblances between magnesium and was among the first to realize that the solution to the zinc and between sulfur and chromium, as shown by problem of pet periodic charts demanded a change in snlfates and chromates, are not so much as su~zested the law to one based upon our knowledge of atomic . . in this chart. structure. After becoming acquainted with Gardner's The strongest objection, however, is that although chart and the other atomic structure charts discussed this chart is an interesting wav of classifving the in the second article, I noticeathat Mitra's goal of a elements, it is not a periodic table. * A periodic tabye is a combination of the periodic table with the table of graphical representation of this important natural law: electron configuration was realized simply by adding to that the properties of the elements are periodic the top of the original form of my chart the s, p, d, f functions of their atomic numbers. The Luder chart divisions of the electrons. I repeat: A chart of the places elements with similar properties in the same elements based upon electron configuration is not vertical column, but i t does not bring out the all- merely another rearrangement of the Mendele& chart. important fact of periodicity; in fact i t abandons It is a modification of the periodic law made necessary periodicity altogether. Hence the completely false by the confusion arising from the many attempts to impression as to the present status of the periodic law merely rearrange Mendeleeff'schart to conform to new registered by the student quoted above. Let us retain experimental facts. the periodic table as a representation of the periodic W. F. LUDER law. N O R T H E A S TUEN~ I V E R S ~ BOSTON. MASSACHUSE~~S WILLIAM E. CADBURY, JR.
Cubic Centimeters a n d Milliliters
To the Editor: Professor Cadbury's imtation is revealed not only by his frank declaration of it, but by the fact that his two principal objections to an electron configuration chart are merely matters of opinion. They are also niutually contradictory. According to Professor Cadbury too many pet periodic charts have been published in recent years, yet this one is not a periodic chart. The whole point of my article lies in this contradiction. The very f a d that so many modifications of Mendeleeff's chart have been suaaested indicates the need of some modification of the ld;ig:nal statement of the periodic law. The article gathered together the
To the Editm: On page 149 of the March number of your excellent Journal, V. T. Jackson makes the claim that the term cubic centimeter is preferable to the "tongue twisting and confusing milliliter" although he admits that the liter has been defined by the International Commission of Weights and Measures as the volume occupied by a kilogram of water a t its maximum density. It is true that the original intent was to make the liter exactly 1000 cubic centimeters and the error in accomplishing this is surprisingly small. Few of us can work within 0.03 of one per cent in any of the measurements we make.