THE ATOM 86 



ceedingly loose structure whose impenetrable por- 

 tions must be extraordinarily minute in comparison 

 with the penetrable portions."^ "Even more open 

 than that of our solar system," another (Aston) 

 describes the structure of the atom. 



A number of atoms have been stripped of their 

 valence, or outer, electrons by Millikan and Bowen. 

 In these experiments, in succession, 1, 2, 3, 4, and 5 

 of the outer electrons were stripped from lithium, 

 beryllium, boron, carbon, and nitrogen, atomic 

 numbers 3 to 7.^ 



Some atoms have been shattered. In 1919, Sir 

 Ernest Rutherford and his assistant, L. B. Loeb, 

 first split the nitrogen atom (by bombarding it 

 with alpha particles).^ Since then it has been 

 shown (by Rutherford, Chadwick and Ellis) that the 

 nuclei of many of the light elements are disinte- 

 grated when struck by very swift alpha particles. In 

 every instance the particle ejected from the atom 

 following an impact of an alpha particle on the 

 nucleus is a single positively charged hydrogen 

 nucleus, or positive electron. The transmutation 

 of elements is a fact of observation, insofar as in 

 the radioactive, uncontrolled (and uncontrollable), 

 changes, an atom through loss of an alpha particle 



^Ihid. 



^ Physical Review, July, 1924. 



* E. Rutherford, Philosophical Magazine, XXXVII (1919). 



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