19, 1 Perkins: The Octet Theory of Valence 3 
cording to the number of electrons. The shells are filled in the 
following order: First shell, 2 electrons; second, 8; third, 8; 
fourth, 18; fifth, 18; sixth, 32; seventh, (32?). (See Table 1). 
The electrons either rotate, perhaps in ring form, or revolve in 
small* orbits, so that they are powerful electro-magnets. ‘(See 
Plate 1.) 
TABLE 1.—The atoms arranged according to their electron. shells. 
3 Hydro-| First |Second/ First |Second| Rare | Uran- 
gen | short | short | long long | earth | ium 
period. | period. | period. | period. | period. | period. | period. | 
Bae eh Elec- Vacen-| 
tronsin} cies in 
Number of shells______ : 1 2 3 4 5 6 7 | shell. | shell. | 
Electrons in kernel-__- 0 2 10 18 386; 64 86 
Completed shell _______ 2 8 s 18 18 82} (82?) 
(* O) | (He2) |(Ne10) | (A 18) |(Kr 36) |(Xe 54) |(Nt 86) | ena 
(H1)| Li3|.Nall/ K19| Rb37| Cs55| * 87 pe oe eers 
Be4 | Mg12; Ca20| Sr88| Ba5dé/} Rags le Hier 
B5| Ali3/} Se21| Yt39! La57|} Ac89 __ Biaath aoe 
Ti22) Zr40|/ Ce68/ Th90 RA ee eA 
V 23) Cbh41| Pr5d9 |Ux291 Biteociccns 
Cr 24 | Mo42| Nd60| Ug2 3 ee 
Mn 25 * 43 pie > Ue Hoenn Spa T loveckgae 
Ba GS to. Bs or aE 
6G G8 teas 2c; Le aaa 90) 
Gd 6th occ PU ieee ees 
PUGS (oo jigs a 
Ho 66 1.2 bi ee 2 Bae 
DY OFA vaendence ee 
D 7, o,f eee geno Be becascoe 
yin By Recent Ses 1B feel 
Tme to pean AR i303 po 
eD Gicdacstiace th gy beer aE 
ta TE fe 10 feces coal 
Tee eke ID) scudese | 
We TE tee io ry Peer 
EES Ammar pe eens 
Fe 26} Ru 44| Os 76 |__..-__- (Se joc. 
Ceo? | Rh 45) ir ?7 |... (a8 
Ni2s|) Pd i6| Pt 78 |._---.-- (10) 345 
Cu 29 | Ag 47 | Au 79 |________ CS Tic 
Zn 30 | Cd 48 | Hg 80 |_______- cP bide maaan 
Ga31| In49/| T181 |_-..-... (18)27 |..i....-} 
C6} Sil¢| Ges2| Sn60| Pb& |__-. 22]. ea | 
NY| P16 | Ass | Obit | Sige 3) 
O8 S16/| Se84| Te52 RaF 84 abe athe 2 
Hi F9| Cli7} Br35 153 bode Se peels emsenees a a a 1 
He2 |Nel0} Al18 | Kr86/| Xe54 | Nt86 |___-____|______.. 0 
* Not yet discovered. 
* Concerning the size of these rings or orbits, there is much difference of 
opinion among physicists. They may be much smaller, relative to the shell, 
than represented in Plate 1, but larger orbits than these seem to be excluded 
by chemical evidence. 
