A NEW PERIODIC TABLE PIERRE VAN RYSSELBERGHE Department of Chemistry, Stanford University, California
A new periodic table, emphasizing the importance of the azimuthal quantum number of the last electron added i n the building u p of the successiwe elements, i s presented. The table consists of a group of subtables corresponding to 1 = 0, 1 , 2, 3, arranged i n such a m y that all the usual relationships between elements are preserved or made more a p a r e n t . The natural sequence of atomic numbers i s thereby sacrificed (as it always i s on account of the rare earths) but can easily be followed by means' of numbers assigned to the warious horizontal lines.
The only missing regularity is the natural succession'of atomic,numbers, but all periodic classifications have to sacri6ce it on account of the rare earths. Moreover, it can easily he restored by reading the horizontal lines in the order indicated by the numbers written on the numbers
"
r
1
0
1-7
I (7' I H2e 1
1
++++++
A
I
S FAR as the author is aware, a periodic chart of
the nature of the one he wishes to present here has never appeared elsewhere. None of the numerous tables shown in the very up-to-date booklet published in the U. S. S. R. for the Mendele& centenary1 is based upon the principle applied here nor is there anything resembling it in the recent monograph by Rabinowitsch and Thilo.= The principle used results from the following considerations. The chemical properties of the.elements depend on the nature ( i . e., the quantum numbers) and on the number of electrons in their respective valence shells. For most elements one of these valence electrons is the one added to the electronic configuration of the preceding element. When some valence electrons belong to a d shell, there are rearrangements with the neighboring s shell (elements Sc 4 Ni: 3d, 4 s 4 e m e n t s Y 4 Pd: 44 5 s 4 e m e n t s La 4Pt: 5d, 6s) or with a neighboring f shell (elements Th, Pa, u 6d, 5f). The chemical properties d ~ p e n dmore on the azimuthal quantum number 1 of the last electron added than on the principal quantum rmmber n. This is particularly well shown by the rare earths, for which the last electrons added correspond to n = 4, 1 = 3. The rare earths are always grouped together in some sort of annex to the periodic table, a situation made particularly imperative by the fact that their atomic numbers are between those of lanthanum and hafnium whose last electron has n = 5, 1 = 2. Since one isolates from the main table the elements for which the last electron added has 1 = 3, why not put in as many separate tables those corresponding to 1 = 2, 1 = 1, 1 = O? This can be done very easily, as shown by our chart, which is self-explanatory. The usual relationships between analogous elements are preserved and are in fact emphasized by this new arrangement. i f e e l e dn eM L ~ ~ bcongress," i l ~ ~1934; available us through the kindness of Dr. J. W. McBain. 3 R ~ ~ ~ ~ o w r E. r s AND c n , TmLo, E., "Periodisches System," Enke, Stuttgart, 1930.
8
-
--- - - --- -1---116 I
I I
I 3
1
--
1 1 1 1 %1 5 I I I I 1 2; 1 1 1 / -1
g Ga Ge 31= 32 -
5
1
6
1
In l3 49 17 TI 81 7
4
2
5
2
6
2
::
I - :fig
I
--------,---,I2
S50o Pb 82
As 33
Se 34
Sb 51 BI 8;
Te 52 Po 84
I 53
Rn
85
El2l&l:ilY; Y
1 ?: 1 1 1 f 1 1 Cb
MO
Ma
39 41 42 43 La(l5')Hf Ta W Re 57 .I. 72 73 74 75 T h Pa 19 A" 8 9 1 9 0 / ~ 1 1 Z I c e Pr ~d 11 sa 58 59 60 61 62 Tb D y Ho Er T" 65 66 67 68 69
86
E I 5; I 2 1 1 '2 I & I %
R"
44
Rh 45
Pd 46
1 1 1 1 1 YbE"63 L"64 1 1 1 1 I 70 1 71
1st period: 2ndperiod: 3rd period: 4th period: 5th period: 6th period: 7th period:
~d
Line 1-Elements 1-2 Lines 2, 3-Elements 3-19 11-18 Lines 4. Lines 6, 7, 8, 9--Elements 1 9 3 6 Lines 10, 11, 12, 13-Elements 37-54 Lines 14, 15, 15', 16, 17-Elements 55-86 Lines 18, 197Elements 87-92
left of the heavy frame lme. Each horizontal line is limited by the frame of the table. For instance, K and Ca on the one hand, Cu and Zn on the other hand, form two distinct horizontal lines, as shown by the different numbers given to these groups.. They are a t t h e same level because the valence electrons have the same quantum numbers. This table apparently satisfies most of the requirements listed by C l a ~ k . It ~ has moreover the distinct advantage over the various spiral classifications, that it CLARX.J. D., J. CHEM.EDUC., 10,675 (1933).
474
grants to each element a square of equal size in which the customary information (atomic number, atomic weight, numbers of isotopes, etc.) could conveniently be tabulated. This is, of course, the common advantage of all the classifications of the original Mendeleeff type. Interesting features of the table are the following. Hydrogen occupies a natural position and its relationship to both lithium and fluorine is made clear by writing its symbol a t the top of the columns of both these elements. All the nou-metals (except H and He) are in the sub-table corresponding to 1 = 1, where they are separated from the other elements by a double Sme. Another double line separates the rare gases from the other nou-metals. The various families (nitrogen group, sulfur group, halogens, rare gases, alkali metals, etc.) are in unintermpted columns. The metals exhibiting magnetic properties are all in the subtables corresponding to I = 2 and 1 = 3. The rare earths
form line 15' which, in the natural sequence of atomic numbers, should be intercalated between La and Hf of line 15. Line 15' is split into two lines of seven elements each in order to condense the table horizontally. Incidentally, this brings out certain known analogies in pairs such as Ce and Tb, Gd and Ln. Several more properties of the table will be noticed by direct inspection. It appears as though a table of this type could profitably be used in the teaching of chemistry. It is simple enough, can easily be reproduced, emphasizes the rBle of quantum numbers in the building up of the periodic system, and lends itself particularly well to the demonstration of the Pauli exclusion principle. The author has used it in lectures on the periodic classification with excellent results. His decision to publish it has been prompted by the absence of any analogous table from the Russian booklet mentioned above, and, hence, from chemical literature as a whole.
