The electron, its isolation and measurement and the determination of some of its properties — John Stuart Mill — John Shaqi
The electron, its isolation and measurement and the determination of some of its properties
John Stuart Mill · en
Precisely the same procedure is repeated in the fifth period of
eighteen elements between krypton and xenon, the rare-earth group which
intervenes between strontium (Sr) and silver (Ag) corresponding to the
elements in which, with increasing atomic number, the added electrons
are filling up the empty orbits in the fourth shell instead of going
into what is now the outer or fifth shell (see Table XV).
Now in considering the sixth period of thirty-two elements from xenon
(Xe) to niton (Nt), a glance at Table XV shows that the fourth shell
in xenon contained only eighteen electrons, whereas in niton there are
thirty-two, i.e., there are fourteen unfilled orbits in xenon in the
fourth shell; and a similar glance at the fifth shell shows
vacant orbits there. The first two elements in this group, viz.,
caesium (Cs) and barium (Ba), take the added electrons in
orbits, then the electrons begin to go inside until gold is reached,
when the fourth and fifth shells become full and from gold (Au) to
niton (Nt), as the added electrons go to the outer shell, the chemical
properties again progress as from sodium to argon, or from copper to
krypton.
It will be noticed that in Fig. 30 element 72 is hafnium, the element
discovered in 1923 by Coster and Hevesy[164] by means of X-ray
analysis. It is because its chemical properties resemble so closely
those of zirconium that it had not been found earlier by chemical
means. Hevesy estimates that it represents one one hundred-thousandth
of the earth’s crust, which makes it more plentiful than lead or tin.
[Pg 226]
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.
[Pg 227]
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