912 Dr. A. 0. Crehore on 



Helium. 



Fig. 7 may represent two helium atoms similar to that 

 of fig. 1, lined up so as to have a common axis o£ rotation. 



M 



m 



2$ 



\m& % 



& s \ 



Fig* 7. — Representing the centres of the charges in two helium atoms 

 coaxial with each other. 



The positive charge of Ae is at 0, the four electrons being 

 A ls A 2 , Bj, and B 2 . Using the method shown in detail above 

 for hydrogen^ the electrostatic force of the atom (A 2 A 1 OB 1 B 2 ) 

 upon the positive charge of the other atom, c, is 



F = ^{(2406 2 -2V>- 4 -f(32806 4 -.1200pa 2 ^ 



He-atom ^ 



-f30yoa 4 >- 6 ...}. . . (38) 



The electrostatic force of the same atom upon the four 

 electrons together (a 2 a 1 b 1 h 2 ) is 



F = j{(-2406 2 +12pa 2 )r- 4 + (-15280M + 36 , 00p^ 2 



He-atom K r 



on four electrona. — 90 / O 2 (2 4 — 15jOa 4 )r -6 . . . }. . . (39) 



The sum of these gives the whole electrostatic force of the 

 second He-atom on the first : 



e 2 

 f = - k \-12pa 2 r-* + (-i2000b±+24:00pa 2 fc-90p 2 a* 



on He-atom. ~h 15/)a 4 )^" 6 . . }. . (40y 



Using the relation 2b — po? as before, (40) becomes 



F =y{-246V- 4 -(7650-60/p)6V- 6 ...}, (41) 



H"e-atom «? 



on He-atom. 



In the above example with hydrogen all the electrostatic 

 terms vanished up to the r" 10 term after introducing the 

 relation (26), but here even the r~ 4 term does not vanish 

 and becomes the largest term, showing great repulsion 



