580 



SCIENCE 



[N. S: Vol. L. No. 1304 



TABLE I 



The Helium — H^ System of Atomic Structure H : 

 He=(4 H)=4.00 



Increment from Series 2 to Series 3 = 4He. Increment from Series 3 to Series 4 = 5 He (4 He for 

 K and Ca) . Increment from Series 4 to Series 5 = 6He. 



Note: The simple helium system begins with carbon (=3 He), and continues with oxygen (4 He), 

 neon (5 He), magnesium (6 He), silicon (7 He), sulphur (8 He), argon (10 He), calcium (10 He), ti- 

 tanium (12 He), chromium (13 and iron (14 He). 



While both the argon and the calcium atom are built from 10 helium atoms, the nucleus of the argon 

 atom contains 10 alpha (a) particles alone, while the nucleus of the calcium atom contains 10 alpha 

 particles with two negative electrons which serve to bind on one of the alpha particles. These may b« 

 called binding electrons. 



The composition of the thorium nucleus is expressed by the formula okEm, that of the nucleus of the 

 uranium atom by a^sKic^s, and that of the isotope of lead which comes from radium as Otihie^j. 



and I wish to show just a little as to the way 

 in which these alpha particles are bound 

 together. 



Eirst, the atomic weights of the lighter 

 atoms of even atomic number beginning with 

 carbon are, 12, 16, 20, 24, 28, 32, 40, 40, 

 48, 52 and 56, the last being the atomic 

 weight of iron, of atomic number 26. Thus 

 the atomic weights of the atoms whose 

 nuclear charge is expressed by an even 

 number, are divisible by 4, the weight of the 

 helium nucleus. If we study the elements of 

 high atomic number, beginning with uranium, 

 which is number 92, we find that the even 

 numbered atoms change into the atom of next 

 lower even number by the loss of a single 

 alpha particle from the nucleus of the atom. 

 Thus we find just the same system of struc- 

 ture indicated by the actual disintegration 

 of the radioactive atoms, as is made evident 



by the atomic weights and the nuclear charges 

 on the atoms of low atomic weight. 



Second, the atomic weights of the elements 

 of odd atomic number point to the idea that 

 their nuclei are compounds of a certain 

 number of alpha particles with three hydro- 

 gen nuclei, so that their formula is na -|- 3h 

 In the exceptional cases of nitrogen the 

 formula is 3a -{- 2h -\- e. 



Four years ago I presented the following 

 formula for the respective nuclei : 



Carbon nucleus = 3a 

 Nitrogen nucleus = 3a + 2ft -f e 

 Oxygen nucleus =4a 

 where t represents a negative electron. 



It is of extreme interest in this connection 

 to note that Sir Ernest Rutherford has just 

 announced that he has been able to bom- 

 bard these atoms with extremely rapid mov- 

 ing alpha particles, and that he has been 



