October 27, 1921] 



NATURE 



^73 





The atomic volume ratios from solids are F = 2S, 

 C1 = 6S, Br = 8S, and I = 128. The differences now 

 agree wiih those of the atomic refractions 



(i) There is a decrease in the atomic volume from 

 carbon to fluorine, silicon to chlorine — that is, against 

 increasing atomic weight. 



(2) The differences between successive members of 

 the same series are equal to the volume of hydrogen 

 (an approximation). 



(3) The difference between the volumes of suc- 

 cessive homologues is n x 36. 



n is 4 between series i and 2. 

 H is 2 ,, ,, 2 and 3. 



H is 2 ,, •» 3 and 4- 



If the masses be compared, there is a difference of 

 2 in the first series and An = 16 (4x4), 44, and 47 

 resfjectively between groups 2 to i, 3 to 2, and 4 to 3. 

 It follows that there is a concentration of matter 

 from within to without, or that members of the first 

 and second series are less condensed than those of 

 succeeding series. 



There is also a difference of 37 between alterna- 

 trve values of a single element : — O 11 and 7-4, A 36, 

 S 25-0 and 21-6, 34, and so on. 



The volumes thus indicate that the elements are 

 built up from discrete parts which are similar for 

 all the elements. The indication is, of course, not 

 exceptionally c'ear, but it is very pronounced. This 

 IS not surprising, seeing that liquids are subject to 

 so many different influences. 



If A.V.'s be plotted against A.M.'s, paraboloid 

 curves are formed (a) at 61, in solid state, (b) at 

 absolute zero b x 10*. Note esf>eciallv the rare gases 

 Xe 76, Ar 144, Kr 177, Xe 228-251, Xit 287 (cf. 

 R. X. Pease, Journ. Amer. Chem. Soc., Mav, 1921)^ 



A periodic relationship also exists between the 

 atomic refractions. Traube was the first to indicate 

 a valency relationship, but in a verv imperfect 



Table of Atomic Refractivities. 



C 



3-36 



Si 

 8-8o 



(0-98) 



(I-04) 



X 



2-38 



5-38 



P 



776 



274 



As 



I0-50 



(0-90) 



(0-97) 



o 

 1-48 



531 



S 



679 



(776) 



Se 



(IO-86) 

 989 



(o-8i) 



^0-83) 



F 



0-67 

 5-29 



CI 

 5 "96 



273 

 Br 



879 



5-08 

 I 



Similar serial and group relationships are noticed 

 in the atomic refractions as in the atomic volumes. 

 First, successive differences of from o-8i to 104 are 

 noticed from element to element in the different 

 series, and this corresponds to the atomic refractivitA- 

 of hydrogen, or, showing a rough proportionalitv to 

 their respective valencies, C 336 (4x084), X '2-36 

 <3xo-79), O 1-48 (2x074), F 1x0-67, Xe o. The 

 atomic refractivities, however, differ considerably in 

 different circumstances. 



The differences between the values for homo'ogues 

 are again a considerable multiple of the unit — 

 n = 4 (4x1-33) between the first and second groups, 

 2 (2 x 1-34) between the second and third groups, and 

 again 4 (4x1-27) between the third and fourth groups. 

 The unit is, however, larger in the group differences 

 than in the serial (o-8i to 106). We'know that there 

 is justification for these multiples from observations 

 on atomic degradation phenomena. Dividing bv 8 the 



NO. 2713, VOL. 108] 



ratio is equal to 0-67, which is similar to the valency 

 value. 



A relation can be found between the atomic refrac- 

 tions for members of the two short series if the 

 number of helium (2) phis latent valency electrons be 

 added to the number of acting valencies. 



r.(Ei) = (He-f L.V.)xo + «(F.V.)xo74 

 r.CC) = 3 approx. Nc = 2 + o + 4 = 6 A.X. = 6 

 r.(F) =074 Nf = 2 + 6+i=9 .A..N. = 9 



y.(E,) = {He+ L.V.)x + 8x0 67 +«;F.V.)x 074 

 ^.(Cl) = 6 Xa = 2 + 6 + 8-t-i = i7A.N.= l7 



f'{^} = 7SS Np =2 + 2 + 8 + 3=15 A.X. = i5 



r.(Br) = 878 NBr = 2 + 6+i2+i=2i 



r.(As) = 7-58 Nas — 2 + 2 + 12 + 3=19 



It is evident that the numbers for members of the 

 third series fall short of the atomic numbers. 



Mn. A.X. 25 XBr2i A4 



V A.N. 23 NxsiQ A4 



Br. A.N. 35 XBr2i A14, or 12, if members of the eighth 

 group number only one (iso- 

 topes). 



As. A.X. 33 Xa^i9 a 14. 



From this it follows that a larger nucleus of the 

 members of the longer series becomes impermeable to 

 light, the number being much greater for even series 

 of period 3. These considerations point to the fact 

 that some central condition produces a repelling power 

 on light-waves of moderate length and speed, whilst, 

 on the other hand, the electrical rather than the 

 material elements tend to retard the light. 



It is thus seen that there is a clear and distinct 

 connection between the atomic volumes, the atomic 

 refractions, the make-up of the elements, and also 

 their evolution from sub-atomic discrete electrified 

 particles. 



The accompanying curve (Fig. i) shows the nature 

 of the relationship in a general way, and this is 

 approximately rectilinear. 



Expressed numerically, this becomes 



V»-V 



R> -R =^'^ 



also 



150 

 5-3 



AV 



The differences — between series are 28, 27, and 



1-2 respectively, the latter being small because r = i 

 for one propertv and 2 for the other. 



aV 



The relation - is equal to j. between successive 



groups. 



The light-waves from the evidence of optical refrac- 

 tivities appear to pass chiefly through the gaps between 

 the atoms A | B | C ( D, as through a grating encoun- 

 tering the valencv electrons which tend to retard them. 

 Onlv single rings of electrons in the first series are 

 affected bv the light-waves, the nuclei not being 

 affected. This is shown by the diminishing refrac- 

 tivities with the increase of atomic m.asses in the 

 regions of the oeriodic system under examination. In 

 the second and subseauent series a shell of electrons 

 (several rings) is influenced. — a similar kernel not 

 being affected, .^nv influence which causes the elec- 

 trons to be drawn more into paths of light (unsatura- 

 tion) results in an increase of the refractivitv. 



If the electrons be suonosed to be distributed in 

 soace, according to principles of equal distribution in 

 the same atom,' with, perhaps, constraining disturb- 



J Octaher'nil models for rare g?ses (sphere*). 



