PERIODICITY PATTERNS of the ELEMENTS K. GORDON IRWIN Colorado State College, Fort Collins, Colorado
The table forms of the Periodic classification, such as writer pernits such yisualizations. Periodicity patterns those of Mendelebff and others, do not readily admit of a for density, metallurgical relations, melting point, actiyity visual presentation of such periodicdies as run counter to of the metals, valence, oxide properties, and fieriodicity family and grou$ lines. The spiral form used by the patterns as applied to analysis groupings are shown.
T
HE SYSTEM of the elements is now recognized as being an entirely continuous one, starting with the element whose atom is the simplest and ending with the one that is most complex. The properties of the elements fit into this continuous plan. Unfortunately no table form of periodic classification is designed to show a steadily changing and unbroken arrangement. All tables, of necessity, are broken up into segments. A chart giving to the arrangement of the atoms a spiral form, fashioned somewhat after the nebulae of astronomy, would seem well worth attention. Such a form fits the needs of modern theory, while retaining the family features of the table forms. What would seem equally important in connection with chemical study, such a spiral form, can be used as a graphical framework for the visual presentation of those periodicities that exist among the elements. The main purpose of the present article is to present such a chart and to show, applied to it, the "periodicity patterns" for several important physical and chemical properties of the elements. The spiral form of the periodic classification devised by the writer and used in the present discussion possesses several features common to the forms of Hackhl and Clark.= It differs from both in having the spiral begin with element 0 (neutron); from Hackh in the treatment of the rare-earth group; from Clark in the treatment of the rare earths, the position of hydrogen, and the family inter-relationships. As shown in Figure 1 the spiral begins with neutron, which is considered as belonging structurally to the inert gas family. Each coil of the spiral represents a period that ends with helium, neon, argon, or some other member of the inert gas family. The number of elements in the periods are: 2, 8, 8, 18, 18, 32, and 6. The rare-earth group is shown as a double loop falling
between cerium (58) and hafnium (72). That this arrangement fits in with the properties of these elements is indicated by the periodicity patterns, to be discussed later.
HACKH, I. W. D., "Chemical dictionary," P. Blakiston's Son In terms of modem theory the elements a t the upper and Co., Philadelphia, Pa., 1929, p. 544. CLARK,J. D., "A new form of periodic chart," J. C n ~ x . left are electron donors, those a t the ripht are electron acceptors; while carbon (6) and silicon (14) near the E~uc., 1 0 , 6 7 5 7 (No"., 1933).
335
center are predominantly electron sharers. An electron reorganization takes place with the rare earths, and with the transition elements a t the bottom of the chart. The radioactivity of elements beyond polo-
VALENCE.
VALENCE
Valence was used as the periodicity basis for Mendele6ff'schart. The periodicity pattern, Figure 2, visualizes the valence situation even better than is the case with the table form. At the upper center are the inert gases with a valence of 0. To the left in the area marked A , and diametrically opposite in the area marked A', the valence advances in a regular order with each element having but a single normal valence toward oxygen. In area B-which extends across the chartthe elements can show more than one normal valence
..
Design by I
