JOURNAL OF CHEMICAL EDUCATION
THE LONG FORM OF THE PERIODIC TABLE GEORGE GLOCKLER and A. I. POPOV State University of Iowa, Iowa City, Iowa
IT 1s a matter of very considerable interest to learn tantalum, and tungsten. Thus the tielines proposed that Professor Coryell ( 1 ) has proposed independently by Coryell between these elements are definitely jnstia long form of the periodic table similar to the one pub- fied. However, it is well known that the inclusion of lished by us (9). I n an article on "The periodic table: the spectral terms of the ground state of atoms in the The 6 d d f 'mixed transition groups" (5) Coryell men- periodic t,able shows that the elements of the same tions a number of interesting points which have to do column usually have the same spectral terms. Although it is not certain that thorium and protacwith the problem of drawing "tie-lines" between elements in the table. In this respect Dr. Coryell differs tinium have any 6 f electrons, Schuurmans (4)found by with us in certain cases. At the outset it should be spectroscopic obsewation, that uranium has three 5 f said that different authors will very likely differ in the electrons in the neutral atom. It is therefore an eelcway these tie-lines should be drawn. It is a matter of tronic homologue of neodymium and some recognition opinion and judgment whether or not a tie-line should of this fact probably should be given in the periodic be a heavy printed line or a dotted line. As a matter of table. fact it would be desirable to shade these tie-lines in Another recent publication (5) shows that the spectra varying degrees to indicate the different relations that of europium and americium are quite similar in appearexist between the elements in question. Coryell points ance and that, therefore, it is very probable that ameriout that the limitations of typography restrict the cium has seven 5felectrons. Therefore, although there possible shadings of meaning it would be desirable t o is very little chemical similarity between the two elements, a tie-line between them is again justified. Perconvey by their use. It has already been pointed out in the previous haps the solid tie-line between tin-hafnium, antimonypublication (t)that any form of the periodic table tantalum, etc., should be replaced by dotted ones. a t best will give only an approximate guide t o the physi- However this equally well applies to the tie-lme becal and chemical properties of the elements. Minor tween copper-silver-gold or between cesium-francium. differences in the structure of the table will he due to In these cases the chemical and physical properties of the personal preferences of the various investigators. elements show much greater variation than, say elePerhaps the only thing that can be asked of a periodic ments of the halogen group. It may be possible t o table is that it would be simple, instmctional, andin- improve the periodic table by varying the shading of the tie-lines t o indicate different degrees of relationelude all the known elements in a single framework. I n these respects there is essentially no difference ship between elements. However, such shading would between our modification and that proposed by Coryell certainly vary from author to author. (1, 5). For example, the position of the neutron can be chosen as suggested by Coryell or by us. I t is LITERATURE CITED located above helium in the latter's table. Its position (1) CORYELL, C. D., Record Chem. Progress, 12, 55 (1951). (2) GWCKLER, G., AND A. I. POPOV,J. CAEM.EDUC.,28, 212 in a "zeroth" row seems t o be a matter of choice. (1851). The positions of thorium, protactinium, and uranium (3) CORYELL, C. D., ibid., 29,62 (1952). in the periodic table have been debated for a long time. (4) SCHUURMANS, P., Physica, 11, 410 (1946). Recent chemical investigations indicate clearly that (5) TOMEINS, F. S., AND M. FRED,J. Opt. Soc. Am., 39, 357 (1949). chemically these elements are homologues of hafnium,
