Hackh — Modification of the Periodic Table. V.)7 



allotropic forms of a nonmetallic character are placed 

 toward the halogen group, thus fitting very well into the 

 system. The melting points given in Table VI follow 

 not so generally a certain direction, nevertheless their 



3B 



5A 



6k 



7A 



1A 



2A 



3A 



5B 



6B 



81 

 Tl 



82 



Pb 



83 

 Bi 



84 

 Po 



85 



86 



Nt 



87 



88 

 Ka 



89 



Ac 



90 

 Th 



91 



Bv 



92 

 U 



(PbRal <— \RaF ) 

 206/ _jf \ 210/ 



(iRaE I 

 , V 210/ , . 

 iPbTKV /ThC\ 

 208\ / 212' 

 PbAcl ^ I AcC 

 RaD j 4 \RaC' 

 , 210/ ,-A \ 214 



hEm 



220 



Ac Em 



RaEm 

 222 



Isotopes of the elements with 

 atomic number 81-92 are the - 

 substances mentioned in the 

 vertical columns. The number 

 of isotopes are given at the 

 bottom of the table. Thus e.g. 

 Pb has 7 isotopes. 



Disintegration takes place in 



two ways: 



C s alpha-radiation, indi- 

 cating loss of He -atom : 

 the elements become more ele- 

 tro -positive and the atomic 

 weight decreases by 4. 



7» » beta-radiation, indi- 

 cating loss of electrons : 

 the elements become more 

 electro-negative, the atomic 

 weight remains the same. 



234 



238 



Table VII. System of radioactive elements, from thallium to uranium. 



periodicity is better exhibited than in the old table. 

 I have used the table in keeping a permanent record of all 

 the nnmerical data about the elements ; each property that 

 can be expressed in a numerical value has its own table, 

 and I have found this method very satisfactory and 

 better than the customary alphabetical tables. New 



Am. Jour. Sci.— Fourth Series, Vol. XLVI, No. 273. — September, 1918. 

 19 



