THE NATURE OF MATTER 167 



neon with ten. In each of these, two of the electrons are in the 

 inner sphere, the remainder in the outer. Now neon has eight 

 in the outer sphere, which seems to be its capacity, and these 

 eight are apparently symmetrically arranged. Neon like helium 

 is very inactive and ends the second series. In the first place we 

 have helium with two electrons in a sphere about the nucleus, then 



Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon 



2+1 2 + 2 2+3 2+4 2 + 5 2+6 2 + 7 2 + 8 



These form what may be termed the second series, the electrons 

 arranged in a second sphere. Again we have a series of eight 

 elements, the third series, each one with one additional electron 

 in its atom, and these seem to be in a third sphere nearly 

 coincident with the preceding one, as follows: 



Sodium 

 2+8+1 



In argon the third sphere is full, 2+8+8. The fourth series is a 

 double series, the electrons being in a sphere with a radius three 

 times that of the helium electrons, therefore capable of holding 

 more electrons. The fourth series ends with krypton. This has 

 two electrons in the first sphere, eight in the second, eight in the 

 third which is nearly coincident with the second, eighteen in 

 the fourth, thirty-six altogether. The fifth series is also a double 

 series, the electrons being in a sphere that is nearly coincident 

 with the fourth, and also has room for eighteen electrons. It 

 ends with xenon, which has fifty-four electrons. The sixth series 

 is a triple series. The electrons are in a sphere with a diameter 

 four times that of the first sphere, which sphere therefore has 

 capacity for 4 2 X2 electrons or 32. Niton, with eighty-six 

 electrons, ends the sixth series. The added electrons of the 

 seventh series are in a sphere coincident with the sixth and 

 therefore with a capacity of thirty-two. However, the later 



