JOURNAL OF CHEMICAL EDUCATION
e
A SPACE MODEL OF THE PERIODIC SYSTEM OF ELEMENTS JENNIE E. CLAUSON Glendale High School, Glendale, California
the various schemes for representing the periodic system of the chemical elements as summarized by Quam and Quam ( I ) , there are space models constructed by Crookes ( B ) , Emerson (S), Soddy (4), Harkins and Hall ( 5 ) , and Schaltenhrand (6). All are variations of the helix, but none gives an adequate position to the rare earths. In the models given by Payne (7). the position of the rare earths has not been improved. He states that the creation of a perfect periodic arrangement is probably impossible. Among the features that he specifies should be present are: 1. A position for hydrogen showing how it is re. lated to the Li-F series. 2. A way of showing the relationship between the left and the right columns of a family. 3. A way of showing the relationship between the inert gases and the elements in the triads. 4. A reasonable position for the rare earths. AMONG
5 . The position of the unfinished series.
In the space model here presented, some of the specifications may he considered to have been met. A wire spiral is fastened to an upright iron support set in a circular hardwood base. Wooden beads strung on the wire represent atoms. On the planed side of each bead is a piece of cloth tape which bears the symbol of the element and its atomic number. On the hase is a chart with radii numbered clockwise, beginning at the left: 0, I, 11, 111, IV, V, VI, VII, I I 1 111' 1 V , I V I Two short radii are inserted between VII-VIII and VIII-I' to accomodate the first and third members of the triads. Two small circles have their diameters on radius 0 and are tangent to the center of the large circle. The curve on this radius is a projection of the wire to show the transition from the neutron to hydrogen to helium. The system begins with the neutron on a vertical
MAY. 1952
extension of wire, placed so that its projection falls on radius 0. The wire below it makes a reverse curve so that hydrogen, placed on its antinode, falls over radius I. Helium is a t the next antinode, in line with the neutron and over radius 0. Lithium follows ahove radius I, as the mire begins a clockwise spiral. Carbon is above radins IV, N over V', 0 over VI', F over T'II', and Ne over radius 0. Another turn of the spiral places Na below Li, Si below C, etc.., finishing with A over radius 0. At this point the spiral enlarges to the full circle of the base, so that elements of the long periods are ahove each radius. The inserted short radii allow places for the triads Fe, Co, Ni and Ru, Rh, Pd, etc. La comes over radius 111, and the lanthanides, finishing with Lu, are placed on a loop of mire that stands vertically in the 111-111' plane. Hf begins another horizontal curve a t radius IV, continuing to radius 111. Here Ac starts another vert,ical loop for the actinides in the 111-111' plane, finishing witah element 103. Symmetry indicates that another curve of the spiral would end with elemeot 118 over radius 0. Perhaps 118 cannot be formed but mould disintegrate into neutrons, in which case the cycle would he complet,e from neutrons to neutrons. Viewed vertically, all the inert elements are above radius 0. All members of family I are above radins I or 1', family I1 is ahove radius I1 or 11', etc., the elements of the short periods being on small circles and the long periods on t,helarge. The lanthanides and the actinides are placed so as to form a continuous part of the system, in a plane a t right angles to the elements in the spiral. Improvements can be made in the model, in addition to truing up the curves. Two parallel plane surfaces could be made on the beads so that the name of the element could be seen from more than one direction. The heads could he colored to bring out certain relationships. The scale adopted r a s merely 'one of convenience, la@ enough to be useful as a classroom teaching device, but not so large as to overburden the rigidity of the mire. Only three sizes of beads were used, although there might he a gradation in sizes to represent increase in atomic volume. This model can he used to show students the essential relationships in the periodic system without bogging them down in detail. There are no makeshifts for accommodating the lanthanides and the actinides. Instead there is a continuity of sequence from the smallest to the largest atom, preceded by the neutron as the first condensation of primordial energy. The numbered heads following californium allow new names to be entered as additional transuranium elements are synthesized. LITERATURE CITED (1) QULM,G. N., AND M. B. QVAM,''Type8 of graphic elassifications of theelements," J. CHEM.EDUC., 11,288-97 (1934). (2) CROOKES, W., "On the position oi helium, argon and krypton in the scheme of elements," Proe. Roy. Soe. (London), 63, 409-11 (1898); Chem. Neu.?, 78,25-6 (1898).
(3) EMERSON, B. K., "Helix Chemica, A d u d y in the periodic relations of the elements and their graphir representation," Am. Chem. J., 4 5 , 166-210 (1809); "The Helix Chemiea," Chem. Reus., 5, 215-29 (1028). (4) SODDY, F., "The Chemistry of the Radio-Elements," Longmans, Green & Co., London, 1914, Part 11. (5) HARKINS,\V. D., ASD K. E. HALL, "Atomic structure V. The periodic s,viitem and the properties of the elements," J. Am. Chem. Soe., 38, 165)-221 (1916). (6) S ~ H A L T E X B RG., ~ N "Darstellung D, den periodisches Systems der Elemente dureh eint. raumlichn Spirde," ibid., 1 1 2 , 2 2 4 1102n> \. ..,.
( 7 ) PAYNE, E. C., "A p w i o d i ~system of the c l ~ m m t s , "J . CHEM. Eouc., 15, 180-:3 (19:38).
