The electron, its isolation and measurement and the determination of some of its properties

by Robert Andrews Millikan

Fig. 30—Bohr’s form of the periodic table, the most illuminating thus far devised. The elements which are in process of orbital reconstruction, because of the passage of electrons into thus far unfilled inner quantum orbits, are inclosed in frames. Lines connect elements which have similar properties.

[TABLE XV]

NUMBER OF ELECTRONS IN DIFFERENT

ORBITS

Period	Z	1₁	2₁	2₂	3₁	3₂	3₃	4₁	4₂	4₃	4₄	5₁	5₂	5₃	5₄	5₅	6₁	6₂	6₃	6₄	6₅	6₆	7₁	7₂
1	1 H	1
	2 He
2	3 Li	2	1
	4 Be	2	2
	5 B	2	2	(1)
	10 Ne	2	4	4
3	11 Na	2	4	4	1
	12 Mg	2	4	4	2
	13 Al	2	4	4	2	1
	18 A	2	4	4	4	4
4	19 K	2	4	4	4	4		1
	20 Ca	2	4	4	4	4		2
	21 Sc	2	4	4	4	4	1	(2)
	22 Ti	2	4	4	4	4	2	(2)
	29 Cu	2	4	4	6	6	6	1
	30 Zn	2	4	4	6	6	6	2
	31 Ga	2	4	4	6	6	6	2	1
	36 Kr	2	4	4	6	6	6	4	4
5	37 Rb	2	4	4	6	6	6	4	4			1
	38 Sr	2	4	4	6	6	6	4	4			2
	39 Y	2	4	4	6	6	6	4	4	1		(2)
	40 Zr	2	4	4	6	6	6	4	4	2		(2)
	47 Ag	2	4	4	6	6	6	6	6	6		1
	48 Cd	2	4	4	6	6	6	6	6	6		2
	49 In	2	4	4	6	6	6	6	6	6		2	1
	54 Xe	2	4	4	6	6	6	6	6	6		4	4
6	55 Cs	2	4	4	6	6	6	6	6	6		4	4				1
	56 Ba	2	4	4	6	6	6	6	6	6		4	4				2
	57 La	2	4	4	6	6	6	6	6	6		4	4	1			(2)
	58 Ce	2	4	4	6	6	6	6	6	6	1	4	4	1			(2)
	59 Pr	2	4	4	6	6	6	6	6	6	2	4	4	1			(2)
	71 Lu	2	4	4	6	6	6	8	8	8	8	4	4	1			(2)
	72 Hf	2	4	4	6	6	6	8	8	8	8	4	4	2			(2)
	79 Au	2	4	4	6	6	6	8	8	8	8	6	6	6			1
	80 Hg	2	4	4	6	6	6	8	8	8	8	6	6	6			2
	81 Ti	2	4	4	6	6	6	8	8	8	8	6	6	6			2	1
	86 Nt	2	4	4	6	6	6	8	8	8	8	6	6	6			4	4
7	87 ——	2	4	4	6	6	6	8	8	8	8	6	6	6			4	4					1
	88 Ra	2	4	4	6	6	6	8	8	8	8	6	6	6			4	4					(2)
	89 Ac	2	4	4	6	6	6	8	8	8	8	6	6	6			4	4	1				(2)
	90 Th	2	4	4	6	6	6	8	8	8	8	6	6	6			4	4	2				(2)
	118 (?)	2	4	4	6	6	6	8	8	8	8	8	8	8	8		6	6	6				4	4

The seventh period begins ([Fig. 30]) with an unknown element of atomic number 87, which, with its single

orbit, should have a valency of 1, then passes to radium with its two