400 



PROTOPLASM 



the hypothesis that electrons, Uke planets, are not only traveling 

 their celestial orbits but spinning on their own axes. 



Name 



Negative electron, or nega- 

 tron 



Positive electron, or posi- 

 tron 



Neutron 



Proton, or hydrogen nucleus 



Alpha particle, or helium 

 nucleus 



Photon, light quantum, 

 X-ray quantum, or 7-ray 

 quantum 



Charge, e.s.u. 



— e 



-4.77 X lO-'" 



4.77 X 10-'° 





 +4.77 X 10-'° 



+e 

 +2e = +2 X 4.77 X 10" 







Mass 



10 2^ grams 



10-27 grams 



1.8 X 10-24 grams 



1.8 X 10-24 grams 



4 X proton 



Newer Theories of Atomic Structure. — Modern theories which 

 substantially modify, indeed in the main replace, the older 

 (Bohr) theory of atomic structure, have been advanced by de 

 Broglie, Heisenberg, and Schrodinger. Important as these 

 newer theories are, it is still true, as Ruark and Urey state, that 

 "the conception of a planetary atom, governed by ordinary 

 mechanics, will remain a useful tool for many years, whatever 

 theoretical developments may be." 



The fundamental concepts of the new physics are the substitu- 

 tion of quantum mechanics (the wave theory) for the older 

 Newtonian mechanics and the substitution of probability for 

 certainty. It had its beginning in the wave theory of motion 

 advanced by the French physicist Louis de Broghe. As in the 

 case of light, physicists found that some phenomena are more 

 easily interpreted if the electron is considered to be a particle, 

 while others are better explained if the electron is regarded as a 

 wave. De Broglie, therefore, suggested that if Hght radiation 

 has the properties of both waves and particles, this might also 

 be true of electrons; that is to say, electrons are corpuscular, yet 

 they move through space by mechanical laws which are not the 

 same as Newtonian mechanics, and this motion can be best 

 represented as the motion of waves. 



The newer physics has gone still further. It tells us that when 

 ideas have to do with things that approach the infinite, they 

 perforce become less and less definite. Imponderables, incom- 



